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smithsonian contributions to paleobiology • number 107

The Geology and Vertebrate 

Paleontology of Calvert Cliffs, 

Maryland, USA – Volume 2

Turtles and Toothed Whales

Edited by

Stephen J. Godfrey

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FRONTISPIECE. Section of Calvert Cliffs north of Randle Cliff, Calvert County, Maryland. Donald J. Morgan III and John 

R. Nance (on ladder) examine fossils from the Miocene Epoch in the Plum Point Member of the Calvert Formation. Photo by 

Stephen J. Godfrey, 13 January 2017; courtesy of Calvert Marine Museum.
smithsonian contributions to paleobiology • number 107

The Geology and Vertebrate 

Paleontology of Calvert Cliffs, 

Maryland, USA – Volume 2

Turtles and Toothed Whales

Edited by

Stephen J. Godfrey

Smithsonian

Scholarly Press

WASHINGTON, D.C.

2023
ABSTRACT

Godfrey, Stephen J., editor. The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA – Volume 2: Turtles and Toothed 

Whales. Smithsonian Contributions to Paleobiology, number 107, viii + 191 pages, frontispiece + 94 figures, 44 life rendering images, 

10 tables, 2023. — This volume is a follow-on to a work published by Smithsonian Institution Scholarly Press in 2018 on the Miocene 

vertebrate fauna from Calvert Cliffs, Maryland, USA. Two chapters are included in this compendium, one on turtles (chelonians) and 

the other on toothed whales (odontocetes). It is anticipated that two more volumes will be needed to complete the taxonomic review. 

Robert E. Weems details the occurrence of 19 kinds of chelonians that have been discovered in the Miocene and Pliocene marine strata 

of Delaware, Maryland, and Virginia, USA, 13 of them in the Calvert Cliffs. The most commonly found remains are those of an extinct 

sea turtle, Trachyaspis lardyi. Remains of four other marine turtles, Procolpochelys grandaeva, Lepidochelys sp., a generically indeterminate cheloniid, and a leatherback turtle (Psephophorus polygonus), are far less common. The other 14 chelonian taxa are nonmarine 

forms that inhabited the land, rivers, and marshes west of the Mid-Atlantic Seaboard during the Miocene. They were washed into the 

coastal marine environments that were then accumulating the sediments exposed today as the strata in the Calvert Cliffs. Stephen J. 

Godfrey and Olivier Lambert review the taxonomically diverse odontocete fauna of 29 named species. Nine of these Miocene taxa 

represent newly named species. Fragmentary remains hint at even greater diversity. Reviewed taxa are restricted to those known from 

along the Calvert Cliffs and other Miocene age deposits on the Atlantic Coastal Plain in Maryland and Virginia, USA. They range in 

age from approximately 22 to 8 Ma and derive from the Calvert, Choptank, and St. Marys Formations. This fauna preserves one of 

the most abundant and diverse assemblages of extinct toothed whales known. None of the named odontocete species included in this 

review are known from beyond the North Atlantic Ocean. In terms of their chronostratigraphic distribution, collectively, they range in 

age from the Aquitanian through the Tortonian, with the large majority occurring within the Burdigalian, Langhian, and Serravallian 

stages (the latter two being the most speciose). The greatest taxonomic diversity occurred during the Miocene Climate Optimum, a time 

(ca. 17–15 Ma) when global average temperatures were as much as 4°C to 5°C above today’s average temperatures, at least for much 

of that interval.

Cover Image: Section of Calvert Cliffs at Rocky Point, Calvert County, Maryland. This cliff includes Miocene-age sediments from 

two formations: the St. Marys Formation comprises the upper half and is resting on the Choptank Formation below. Photo by Dave 

Williams, 7 October 2007; courtesy of Calvert Marine Museum.

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Library of Congress Control Number: 2023935694

ISSN: 1943-6688 (online); 0081-0266 (print)

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for Printed Library Materials Z39.48–1992.
I dedicate this volume to David “Dave” J. Bohaska, 

recently retired from the Department of Paleobiology, 

National Museum of Natural History, Smithsonian Institution.

For 25 years, Dave has helped me (and innumerable visitors 

and researchers, including my coauthor Olivier Lambert since 

his first visit in 2002) in so many ways just about every time we 

visited the fossil cetacean collection. Dave’s intimate knowledge 

of the national collection helped move this volume forward.

Thank you, Dave!

(Photo by George N. Bohaska.)

Dedication

David “Dave” J. Bohaska

(2023)

Contents

INTRODUCTION by Stephen J. Godfrey 1

1 Miocene and Pliocene Chelonians from the Calvert Cliffs 

and Nearby Regions 3

Robert E. Weems

2 Miocene Toothed Whales (Odontoceti) from Calvert Cliffs, 

Atlantic Coastal Plain, USA 49

Stephen J. Godfrey and Olivier Lambert

INDEX 187

INTRODUCTION

When the first volume of The Geology and Vertebrate Paleontology of Calvert 

Cliffs, Maryland, USA was published in 2018 (Godfrey, 2018), it was anticipated that a companion volume would include the balance of the vertebrate 

taxa that have been found along Calvert Cliffs and in other Miocene sediments that crop 

out in southern Maryland and northern Virginia. At that time, no one imagined a global 

pandemic and the delays that it could have on the completion of this extended project. 

Well, COVID-19 happened, and for more than two years (and at the time of this writing), 

the collections in the Department of Paleobiology at the Smithsonian have been closed and 

inaccessible to most researchers. Consequently, without access to many critical specimens 

in that collection, several chapters came to a screeching halt. In addition to which, with sadness we also marked the passing of Dr. Storrs Lovejoy Olson, long-time curator of birds at 

the Smithsonian, prolific author, and expected contributing coauthor to the review chapter 

on the Miocene fossil birds from Calvert Cliffs.

Nevertheless, several authors were able to forge ahead in spite of the limitations imposed by the pandemic, very fortunately having collected, prior to the Smithsonian shutdown, the information and images necessary for the completion of their reviews. Although 

several other chapters are nearing completion, it was decided that the two chapters included in this volume were of sufficient length to warrant publication in a single volume. 

Consequently, at least one and perhaps two additional volumes are anticipated to complete 

this review, with a principle focus on the known diversity, of the Miocene-age vertebrates 

preserved in the shallow marine sediments that comprise Calvert Cliffs.

In chapter 1, Robert E. Weems details the occurrence of 19 species of turtles 

(chelonians) that have been discovered in the Miocene and Pliocene marine strata of 

Delaware, Maryland, and Virginia, USA, 13 of them in the Calvert Cliffs. What was 

unexpected is that of these 19 species, 14 are nonmarine turtles that inhabited the land, 

rivers, and marshes west of the Mid-Atlantic Seaboard during the Miocene. Occasionally, these turtles were washed into the coastal marine environments that were then 

accumulating the sediments exposed today in part as the strata along Calvert Cliffs. One 

new species is named.

Chapter 2, coauthored by Stephen J. Godfrey and Olivier Lambert, contains descriptions of the 29 named species of extinct toothed whales (odontocetes) known from the 

Miocene marine strata in coastal Maryland and northern Virginia. Additional fragmentary 

and unnamed specimens evidence even greater diversity. This fauna preserves one of the 

most abundant and diverse assemblages of extinct toothed whales known. Sixty-two percent of the Miocene odontocetes from Maryland and Virginia are endemic to this region, 

Curator of Paleontology, Department of Paleontology, Calvert Marine Museum, P.O. Box 

97, Solomons, Maryland 20688, USA; Research 

Associate, Department of Paleobiology, National 

Museum of Natural History, Smithsonian Institution, Washington, D.C. 20013-7012, USA.

*Correspondence: 

Stephen.Godfrey@calvertcountymd.gov

Received 7 May 2020; accepted 15 December 

2022.

The Geology and Vertebrate Paleontology of 

Calvert Cliffs, Maryland, USA – Volume 2

Turtles and Toothed Whales

Edited by Stephen J. Godfrey*
2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

83% are known only from the western North Atlantic, and 100% 

are known only from the North Atlantic Ocean. The greatest 

taxonomic diversity occurred during the Miocene Climatic Optimum, a time (ca. 17–15 Ma) when global average temperatures 

were as much as 4°C to 5°C above today’s average temperatures, 

at least for much of that interval.

Both chapters highlight the contributions of amateur 

and professional paleontologists. In chapter 1, a professional 

paleontologist found the one newly named species. In chapter 2, 

nine new species are named, the type specimens of which were all 

found by amateur paleontologists. If ever there were testament 

to the ongoing contributions that the amateur paleontological 

community can make in helping to advance our knowledge of 

paleontology, it would be these type specimens and the resulting 

newly named species. That collaborations with members of the 

amateur community (many of whom have a self-taught expertise 

in paleontology) could be so wonderfully synergistic was not a 

part of my formal paleontological education. That realization 

came only over time by getting to know individuals in that 

community, by working with members of our fossil club (many of 

whom have contributed, and continue to contribute, to our fossil 

club newsletter, The Ecphora) and our departmental volunteers, 

and by being receptive to their offers to help and donate specimens 

to the Calvert Marine Museum. Thankfully, there are now many 

resources to help foster amateur–professional collaborations in 

the field of paleontology (to list just a few, MacFadden et al., 

2016; Boessenecker, 2022; myFOSSIL, 2022).

Our first volume (Godfrey, 2018) was dedicated to the 

local landowners who have so generously allowed professional 

paleontologists to quarry fossils from their cliff-front properties and 

the amateur/avocational collectors who have contributed so many 

scientifically important fossils to both the Calvert Marine Museum 

and the Smithsonian Institution’s National Museum of Natural 

History. In addition to recognizing once again the very important 

contributions both of these groups have made to the preservation 

of the fossils included in this volume, I further dedicate this work to 

the citizens of Calvert County, who help to fund the Calvert Marine 

Museum, and American taxpayers in general for their ongoing 

financial support of the Smithsonian Institution.

A WORD OF WARNING

As in the first volume (Godfrey, 2018), I include here this important word of warning! “Digging in the cliffs is dangerous and 

is prohibited on all state and federal lands” without obtaining permits. “On private land, permission must be obtained from the owners before digging. If you see a skull, bone, or unusual fossil in the 

cliffs, please report it to the Calvert Marine Museum in Solomons, 

Maryland (telephone, 410-326-2042). The museum appreciates 

getting this information and, if justified by the importance of the 

find, will make every effort to obtain the necessary permission and 

have trained personnel collect the specimen, giving full credit to the 

finder” and property owner (Ashby, 1979:16).

ACKNOWLEDGMENTS

I am exceedingly fortunate and honored to be a research 

associate within the Department of Paleobiology at the 

Smithsonian Institution. Nick Pyenson has been my sponsor for 

many years, for which I am very grateful. Without his support 

for my tenure as a research associate, publishing with the 

Smithsonian Institution Scholarly Press (SISP) would not have 

been possible. Many thanks, Nick! Once again, I have been 

blessed to work with Ginger Minkiewicz, director of SISP, to 

bring this publication to fruition. Furthermore, Myka Bangert, 

program assistant at SISP, was always ready to provide logistical 

and technical support. Other members of the SISP production 

team include publications specialist Meredith McQuoidGreason, freelance copyeditor Tshawna Byerly, and freelance 

typesetter Claire Purnell. I am very grateful for their attention to 

detail. I also express my appreciation to the Editorial Board of 

SISP, who pushed for excellence, resulting in a better publication 

than I had originally envisioned.

I also sincerely thank the other contributing authors, 

Olivier Lambert and Robert E. Weems, for their detailed reviews 

and extraordinary patience in light of COVID-19 delays. The 

artistic excellence of Brenna Litynski and Tim Scheirer is evident 

throughout. Their life renderings have helped to enliven the 

Miocene vertebrates reviewed herein. John Nance (paleontology 

collections manager at Calvert Marine Museum [CMM]) also 

helped in many ways.

I am also indebted to Jeffery Murray (CMM director) 

and Rachelle Green (CMM deputy director and my immediate 

supervisor) for their ongoing support for work like this. The 

curatorial position at the CMM is made possible with funding 

from the citizens of Calvert County, Maryland, and the County 

Board of Calvert County Commissioners. Additional funding for 

the Department of Paleontology comes from the Clarissa and 

Lincoln Dryden Endowment for Paleontology.

REFERENCES

Ashby, W. L. 1979. Fossils of Calvert Cliffs. Calvert Marine Museum Special 

Publication 2. Solomons, Md.: Calvert Marine Museum.

Boessenecker, R. W. 2022. Amateur Collectors Are Critical to the Study of Fossil 

Vertebrates: A Case Study from Two Neogene Localities in Northern 

California (Santa Margarita and Purisima Formations). Palaeontologia 

Electronica, 25(1):a10. https://doi.org/10.26879/1199

Godfrey, S. J., ed. 2018. The Geology and Vertebrate Paleontology of Calvert 

Cliffs, Maryland, USA. Smithsonian Contributions to Paleobiology 100. 

Washington, D.C.: Smithsonian Institution Scholarly Press. https://doi.

org/10.5479/si.1943-6688.100

myFOSSIL. 2022. https://www.myfossil.org/ (accessed 18 April 2022).

MacFadden, B. J., L. Lundgren, K. Crippen, B. A. Dunckel, and S. Ellis. 2016. 

Amateur Paleontological Societies and Fossil Clubs, Interactions with Professional Paleontologists, and Social Paleontology in the United States. Palaeontologia Electronica, 19(2):19.2.1E. https://doi.org/10.26879/161E
ABSTRACT. Nineteen kinds of chelonians have been discovered in the Miocene and Pliocene marine strata of Delaware, Maryland, and Virginia, 13 of them in the Calvert Cliffs. 

The most commonly found remains are those of an extinct sea turtle, Trachyaspis lardyi. 

Remains of four other marine turtles, Procolpochelys grandaeva, Lepidochelys sp., a generically indeterminate cheloniid, and a leatherback turtle (Psephophorus polygonus), are far 

less common. The other 14 chelonian taxa are nonmarine forms that inhabited the land, 

rivers, and marshes west of the Mid-Atlantic Seaboard during the Miocene and Pliocene. 

They were occasionally washed into the coastal marine environments that were then accumulating the sediments exposed today as the strata in the Calvert Cliffs. Although rare, these 

nonmarine turtle finds provide significant insight into the onshore turtle fauna that lived 

in Delaware, Maryland, and Virginia at that time. Nonmarine turtles found in the Calvert 

Cliffs include two genera and three species of tortoises: Hesperotestudo ducateli, Floridemys 

hurdi, and Floridemys nancei sp. nov. Pond and river turtles are represented by a side-necked 

turtle (Bairdemys miocenica), one or more musk turtles (Kinosternidae indet.), a softshell 

turtle (Apalone cf. A. ferox), and a painted turtle (Chrysemys isoni). Seven other species of 

nonmarine turtles are known from Miocene and Pliocene strata exposed elsewhere in the 

Delaware-Maryland-Virginia region: a softshell turtle (Apalone lima), a chicken turtle (“Deirochelys” carri), a map turtle (Graptemys sp.), a slider turtle (Trachemys inflata), two cooters 

(Pseudemys caelata and Pseudemys williamsi), and a tortoise (Hesperotestudo williamsi). 

The documented Miocene and Pliocene turtle fauna from Delaware, Maryland, and Virginia 

(13 taxa from the Calvert Cliffs plus 6 taxa from elsewhere) is almost as diverse as the turtle 

fauna living today in the Delaware, Maryland, and Virginia Piedmont–Coastal Plain regions 

(20 taxa). Seven of these Miocene and Pliocene chelonian genera are now extinct (Bairdemys,

Floridemys, Hesperotestudo, Procolpochelys, Psephophorus, Trachyaspis, and the indeterminate cheloniid genus), whereas seven other genera still inhabit this region (Apalone, Chrysemys, Deirochelys, Graptemys, Lepidochelys, Pseudemys, and Trachemys).

1 Miocene and Pliocene 

Chelonians from the Calvert 

Cliffs and Nearby Regions

Robert E. Weems* 

Research Associate, Department of Paleontology, 

Calvert Marine Museum, Solomons, Maryland 

20688, USA. 

*Correspondence: rweems4@gmail.com

Received 7 May 2020; accepted 15 December 

2022.
4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

INTRODUCTION AND TAXONOMIC HISTORY

Turtle remains are fairly common in the Miocene strata of 

the Calvert Cliffs, but they are often overlooked because many 

of their remains are small in size and even the larger specimens 

tend to break up badly when washed out of the cliffs. Not surprisingly, the most common turtle remains found in the marine 

strata of the Calvert Cliffs are those of marine turtles. Other 

turtle remains, which represent animals that lived either in fresh 

water or on land, are much less commonly found but provide 

valuable insights into the onshore chelonian fauna that existed 

immediately west of the shallow seas that covered most of the 

Delaware, Maryland, and Virginia Coastal Plains during much 

of the Miocene epoch. Nineteen kinds of Miocene and Pliocene turtles are documented here from this region, 13 of which 

have been found in the Calvert Cliffs (Figure 1.1, locality 4). 

This fauna demonstrates that turtles were about as diverse in the 

mid-Atlantic region during the Miocene and Pliocene as they are 

today, with 20 kinds of turtles inhabiting this region. 

The earliest report of Miocene turtles from Maryland was 

by Cope, who in 1867 reported two types of sea turtle remains 

from Miocene Calvert Formation strata near the Patuxent River 

(Cope, 1867; Figure 1.1, locality 3). He referred these specimens 

to “Chelone sp.” and placed them in the collections of the Philadelphia Academy of Natural Sciences. Unfortunately, these specimens cannot be located today and apparently have been lost, 

but on the basis of their descriptions by Cope, Weems (1974) 

surmised that they probably pertained to the turtles now called 

Trachyaspis and Procolpochelys. Almost 30 years later, Cope 

(1896) described a Miocene sea turtle from Hanover County, 

Virginia, that he named Syllomus crispatus on the basis of two 

costal fragments with vermiform external sculpturing and a 

highly distinctive humerus (illustrated in Hay, 1908: fig. 269). It 

was not until 1936 that Berry and Lynn described a second sea 

turtle with vermiform carapace sculpturing and prominent costoperipheral fontanelles that they named Peritresius virginianus. 

That same year, Collins and Lynn (1936) described a third sea 

turtle specimen with vermiform carapace sculpturing and prominent longitudinal carapace ridges that they named Chelonia 

marylandica. Although each of the type specimens of these three 

nominal species do show real differences, subsequent collecting 

has shown that these differences represent only variants within a 

single population of sea turtles and that these differences mostly 

reflect changes in carapace morphology due to growth and, to a 

lesser degree, a very variable development of longitudinal ridges 

on the carapace in this species (Weems, 1974).

In addition to synonymizing these variant nominal species described from Maryland and Virginia, Weems (1974) 

recognized two other nominal species that had been erected 

for the same taxon of Miocene sea turtle: Trachyaspis aegyptiaca (Lydekker, 1889) from Egypt and Kurobechelys tricarinata

Shikama, 1956 from Japan. As Kurobechelys tricarinata was not 

named until 1956, Weems (1974) concluded that it was a junior 

synonym of Syllomus aegyptiacus. The taxon Trachyaspis lardyi 

was erected by Meyer in 1843 for a turtle costal from Italy, but 

Weems (1974) did not believe that T. lardyi was a sea turtle and 

so concluded that T. aegyptiaca, which was a sea turtle, was 

incorrectly assigned to this genus. Therefore, he synonymized 

all of this material under the binomen Syllomus aegyptiacus on 

the basis of the oldest generic and specific names applied to the 

material he studied. More recently, however, Lapparent de Broin 

(2001) and Chesi et al. (2007) showed that the type species of 

Trachyaspis, T. lardyi Meyer, 1843, is a sea turtle and that its 

generic and species names have priority over all other names applied to this turtle material. Thus, the proper name for this taxon 

is Trachyaspis lardyi.

The first Miocene sea turtle species described from anywhere in the Atlantic Coastal Plain came from the Kirkwood 

Marl of New Jersey. It was named Chelonia grandaeva by Leidy 

(1851), but this species was later referred to a new genus under 

the binomen Procolpochelys grandaeva by Hay (1908). The very 

fragmentary type material of this genus and species was not successfully described until a paper by Zangerl and Turnbull (1955) 

did so on the basis of several fairly complete carapace and plastron 

specimens that were reassembled from the numerous type fragments. For well over a century, this taxon was not recognized outside of New Jersey until Weems (1974), on the basis of specimens 

he discovered in the Calvert Formation in the Horsehead Cliffs 

of Westmoreland County, Virginia (Figure 1.1, locality 1), finally 

established that this species also occurs in Miocene strata in the 

Northern Neck of the Virginia Coastal Plain. Since then, further 

remains of Procolpochelys have shown up in the Calvert Cliffs; in 

the cliffs south of Popes Creek, Maryland (Figure 1.1, locality 2); 

and in Calvert strata exposed along the Pamunkey River in east 

central Virginia (locality 3 in fig. 1 of Weems and George, 2013). 

These remains are described and discussed herein.

Remains of leatherback sea turtles were first reported from 

upper Shattuck-Zone 9 (just below Shattuck-Zone 10) in the 

Calvert Cliffs by Palmer (1908), who described a substantial but 

still fragmentary portion of a leatherback carapace under the 

name Psephophorus calvertensis. Since then, the only other published report of a leatherback turtle was by Weems (1974), who 

pointed out that a fragmentary turtle scapula reported by Case 

(1904) as “Chelone sp.” from the Miocene of Maryland actually 

is a scapula of Psephophorus. Occasional remains of leatherback 

turtles, usually isolated dermal platelets or small patches of dermal platelets, have continued to be found with regularity in the 

Maryland Miocene. However, only two specimens found in the 

cliffs south of Popes Creek, Maryland, are complete enough to 

add to our understanding of this species.

A nonmarine Maryland Miocene turtle was first reported 

by Cope (1867) from the Patuxent River area; he gave this material the name Trionyx cellulosus. Unfortunately, Cope did 

not illustrate this material, and it has apparently since been 

lost; it is now considered to be a nomen vanum (Hay, 1908; 

Weems and George, 2013). Soon after, however, he named another new species of softshell turtle, Trionyx lima, from the 

“Miocene marl” of New Jersey (Cope, 1869a, 1869b, 1869c) 
NUMBER 107 • 5

FIGURE 1.1. Map showing major localities from which turtle remains have been found in the Calvert Cliffs and nearby areas. (1) Horsehead, Stratford, and Nomini Cliffs, located near Stratford Hall and Wakefield in Westmoreland County, Virginia, along the right (south) 

bank of the Potomac River. (2) The Popes Creek bluffs, located in Charles County, Maryland, along the left (east) bank of the Potomac 

River. (3) The Thomas Residence, located in Charles County, Maryland, near the right (west) bank of the Patuxent River; this is the area 

from which the earliest Maryland Miocene sea turtle remains were reported. (4) The Calvert Cliffs, located along the western shore of 

Chesapeake Bay in Calvert County, Maryland.
6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

that was illustrated by Hay (1908); this taxon remains valid. As 

discussed in Weems and George (2013), the generic name Trionyx is no longer considered to be appropriate for any middle 

or late Cenozoic softshell specimens from North America, so 

this species is now designated as Apalone lima (Cope, 1869). 

In 1936, Collins and Lynn described two species of nonmarine turtles found in Shattuck-Zone10 of the Calvert Cliffs: 

one was a tortoise that they named Testudo ducateli, and the 

other was a side-necked turtle that they named Taphrosphys 

miocenica. In recent years, Weems and George (2013) assigned 

Testudo ducateli to the genus Hesperotestudo as Hesperotestudo (Caudochelys) ducateli (Collins and Lynn, 1936). Similarly, Taphrosphys miocenica has been taxonomically updated 

(Weems and Knight, 2012) and is now assigned to the genus 

Bairdemys as Bairdemys miocenica (Collins and Lynn, 1936). 

In more recent years, Holman (1998) and Weems and George 

(2013, 2014) have recognized five more kinds of nonmarine 

turtles from the Calvert Formation: Kinosternon sp. (here 

modified to Kinosternidae indet.), Floridemys hurdi, Hesperotestudo (Caudochelys) williamsi, Chrysemys isoni, and Trachemys sp. Except for Floridemys hurdi, which came from the 

Calvert Cliffs, the other new taxa came from the lower Calvert 

Formation Pollack Farm site in Delaware, the lower Calvert 

Formation Popes Creek bluffs in Maryland, and the lower Calvert Formation outcrops along the Pamunkey River in Virginia. 

More new finds of Miocene turtles in the Calvert, Choptank, St. 

Marys, and Eastover Formations (Figure 1.2) are described and 

discussed here for the first time, including a new species (Floridemys nancei sp. nov.) from the St. Marys Formation. Five taxa 

of turtles (Apalone lima, “Deirochelys” carri, Pseudemys williamsi, Pseudemys caelata, and Hesperotestudo williamsi) are 

not known from the Calvert Cliffs, but they may well be found 

there in the future. The Pliocene taxon Graptemys sp. is likely 

too young to have been present during the Miocene, when the 

sediments of the Calvert Cliffs were accumulating, but it is also 

discussed here for the sake of completeness.

Museum Abbreviations

AMNH American Museum of Natural History, New York, 

New York, USA

ANSP Academy of Natural Sciences Philadelphia, Philadelphia, Pennsylvania, USA

CMM Calvert Marine Museum, Solomons, Maryland, USA

HSMC Historic St. Mary’s City, St. Mary’s City, Maryland, 

USA

NHMW Naturhistorisches Museum Wien, Vienna, Austria

PU Princeton University, Princeton, New Jersey, USA

UF University of Florida, Gainesville, Florida, USA

USNM National Museum of Natural History (formerly the 

U.S. National Museum), Smithsonian Institution, 

Washington, D.C., USA

Other Abbreviations

ICZN International Code of Zoological Nomenclature

SZ Shattuck-Zone

SYSTEMATIC PALEONTOLOGY

Class Reptilia Laurent, 1768

Order Testudines Linnaeus, 1758

Suborder Pleurodira Cope, 1864

Superfamily Pelomedusoides Cope, 1868a

Family Podocnemididae Cope, 1868b

Supergenus “Shweboemys Group” sensu Meylan, 1996

Genus Bairdemys Gaffney and Wood, 2002

Turtle – Bairdemys – Podocnemidi

Bairdemys miocenica (illustration by Brenna Litynski)

Shell of Bairdemys healeyorum (Weems and Knight, 2012)
NUMBER 107 • 7

Type Species. Bairdemys hartsteini Gaffney and Wood, 2002.

Bairdemys miocenica (Collins and Lynn, 1936)

Taphrosphys miocenica Collins and Lynn, 1936:155–162 (original description).

Bothremys sp. Gaffney and Zangerl, 1968:208–209.

Bothremys sp. Zug, 2001:207.

“Taphrosphys” miocenica Gaffney et al., 2006:110–111.

Bairdemys miocenica Weems and Knight, 2012:298–300.

Bairdemys miocenica Weems and George, 2013:585.

Holotype. USNM 13784, anterior plastron (epiplastra, entoplastron, and hyoplastra) of a single individual.

Holotype Locality and Horizon. 0.4 km 

(0.25 mile) south of Camp Roosevelt along the Calvert Cliffs, 

Calvert County, Maryland; SZ 10 (Shattuck, 1904), Calvert Formation; early Middle Miocene (early Langhian, ca. 15–16 Ma; 

Weems and Edwards, 2007).

Diagnosis. Anterior lobe of plastron short, broad, and 

rounded with well-developed but rather thin axillary buttresses, 

maximum length of hyoplastra about equal to their breadth, mesoplastral contact with hyoplastron indicates that mesoplastra 

FIGURE 1.2. Miocene stratigraphic units present in the Coastal Plain of Virginia and Maryland. Nearly all of these units, ranging in age 

from about 21 to 6 Ma, were deposited in shallow to mid-shelf marine environments. The most offshore environments are present in transgressive cycle E of the Plum Point Member (Calvert Formation) and in transgressive cycle C of the Conoy Member (Choptank Formation). 

Three transgressive cycles do not have Shattuck Zone (SZ) numbers because Shattuck (1904) did not recognize transgressive cycle C in the 

Fairhaven Member and because he did not study the Eastover Formation, which does not appear to be present in Maryland. Transgressive 

cycles and packages of SZs are adapted from Weems et al. (2017). Because the zones that Shattuck named were not defined the same way 

as zones are defined in modern stratigraphic usage, they are called “Shattuck-Zones” in this chapter.
8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

were relatively small, located far from the midline, and rather 

polygonal in shape. Intergular scute small, pentagonal, mostly 

located on the epiplastra, and only slightly projecting backward 

onto the entoplastron; gular scutes small, triangular, and located 

far forward on only a small part of the epiplastra; humeral scutes 

also relatively small and forwardly located, meeting along the 

midline beneath the intergular; pectoral scutes large, covering 

the anterior two-thirds of the hyoplastra and the posterior twothirds of the entoplastron and extending forward onto the posterior parts of the epiplastra. Nuchal much wider at rear than at 

front, being anteriorly constricted by encroachment of the first 

peripherals; cervical scute not present. Caput of humerus elongated roughly along the axis of the humeral shaft, which is rather 

thick and stout.

Previously Referred Material. USNM 186773, 

nuchal, xiphiplastron fragment, and humerus, from Pungo River 

Formation, Lee Creek Mine (presently known as the Aurora Mine), 

Aurora, North Carolina, described and illustrated in Zug (2001).

Newly Referred Material. CMM-V-1765, second 

or third neural element. Collected from the Calvert Cliffs by James 

Kaltenbach about 1.2 km (0.75 mile) south of Plum Point Road in SZ 

10, Plum Point Member, Calvert Formation (basal Middle Miocene).

Remarks. The type material and referred elements are 

shown in Figure 1.3. Remains of Bairdemys miocenica are quite 

rare in the Miocene of the mid-Atlantic region, and in the Calvert Cliffs they have shown up only in SZ 10. The only other 

known specimens of this species came from the Lee Creek Mine 

(Zug, 2001); they almost certainly came from the Pungo River 

FIGURE 1.3. (A) Holotype anterior plastron of Bairdemys miocenica (USNM 13784) in ventral (external) view with 

sulcal grooves darkened for clarity and scutes named. (B) Referred left xiphiplastron fragment of Bairdemys miocenica

(USNM 186773) in internal view showing pubic scar. (C) Referred nuchal of Bairdemys miocenica (USNM 186773) 

in dorsal (left) and ventral (right) views. (D) Referred humerus of Bairdemys miocenica (USNM 186773) in dorsal 

(left) and ventral (right) views. (E) Referred second or third neural element of Bairdemys miocenica (CMM-V-1765) 

in dorsal (left) and lateral (right) views.
NUMBER 107 • 9

Formation, which is correlative with the lower Calvert Formation. Bourque (2016) has suggested that Miocene occurrences 

of side-necked turtles in North America represent episodic invasions by Central American or Caribbean populations that entered 

North America during exceptionally favorable, frost-free climatic 

intervals but failed to remain established here for long. The very 

restricted stratigraphic occurrence of Bairdemys in Maryland during the Miocene Climatic Optimum supports this idea. It has been 

proposed in recent years that the stereogenyin turtles (including 

Bairdemys) are a marine-adapted branch of the podocnemidian 

turtle group (Ferreira et al., 2015). If true, this would also help 

explain the episodic reoccurrence of Bairdemys throughout the 

Miocene marine column of the Chesapeake Group.

Suborder Cryptodira Cope, 1868

Family Kinosternidae Hay, 1892

Turtle – Kinosternidae

Kinosternon sp. (illustration by Brenna Litynski)

Shell of Kinosternon pannekollops (after Bourque, 2015)

Kinosternidae indet.

Kinosternon sp. indet. Holman, 1998:141–142.

Kinosternon sp. Weems and George, 2013:572–576.

Kinosternidae indet. Bourque, 2015:842. 

Kinosternon sp. Bourque and Schubert, 2015:16. 

Kinosternon sp. Joyce and Bourque, 2016:34.

Previously Referred Material. One complete 

and one fragmentary left sixth costal, one left hyoplastron, two 

left and one right hypoplastra (USNM 483389), collected by 

George Simonson, David “Dave” J. Bohaska, Ralph E. Eshelman, and Robert “Bob” Purdy from the Fairhaven Member, 

Calvert Formation, Pollack Farm site, Delaware (Weems and 

George, 2013).

Newly Referred Material. (1) Two peripheral 

elements (CMM-V-2546), collected by Elma Williams Andres, 

probably derived from SZ 14, Plum Point Member, Calvert Formation; Kenwood Beach, Calvert County, Maryland. (2) Two 

neurals (CMM-V-8750), collected by Jeff O’Neil, Little Cove 

Point Member, St. Marys Formation, Chesapeake Ranch Estates, 

Calvert County, Maryland. (3) Neural (CMM-V-8751), collector unlisted, Little Cove Point Member, St. Marys Formation; 

Chesapeake Ranch Estates, Calvert County, Maryland. 

Description. Carapace fragments thick; median 

neural and lateral costal keels absent; anterior musk duct groove 

on the third peripheral inferentially extends forward onto the 

unknown second peripheral and backward onto the unknown 

fourth peripheral; plastron has a well-developed hinge line 

on the anterior border of the hyoplastron; entoplastron 

absent; presence or absence of a hinge line on the posterior 

border of the hypoplastron uncertain; xiphiplastra inferred to 

be narrow.

Remarks. The small size of kinosternid turtles makes 

their bones and shell elements easy to miss or overlook. Even 

so, a number of specimens have come to light, most notably at 

the Pollack Farm site in Delaware (Holman, 1998; Weems and 

George, 2013). Neural elements were not represented among 

the Pollock Farm material, but the Calvert Cliffs material does 

include several (Figure 1.4C–E), none of which show any evidence of a keel. The external surface of the shell elements has 

a somewhat porcelaneous texture, which is not commonly seen 

in other Calvert Cliffs turtles. Although Holman (1998) and 

Weems and George (2013) considered this material to be referable to the genus Kinosternon, Bourque (2015), Bourque and 

Shubert (2015), and Joyce and Bourque (2016) concluded that 

this material can be confidently assigned only to the family 

Kinosternidae. This more conservative view is adopted here.
10 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
NUMBER 107 • 11

Family Trionychidae Gray, 1825

Genus Apalone Rafinesque, 1832

Turtle – Apalone – Trionychidae

Apalone ferox (illustration by Brenna Litynski)

Shell of Apalone spinifera (The Fossil Forum, 2016)

Type Species. Apalone ferox (Schneider, 1783).

Apalone cf. A. ferox (Schneider, 1783)

Apalone ferox Auffenberg, 2001:124.

Referred Material. (1) Distal costal fragment 

(CMM-V-3570), collected by Lum F. Douglass from the Little 

Cove Point Member, St. Marys Formation; Chesapeake Ranch 

Estates north of Driftwood Beach, Calvert County, Maryland. 

(2) Costal fragment (CMM-V-4531), collected by John R. Nance 

from the Little Cove Point Member, St. Marys Formation; 

Chesapeake Ranch Estates north of Driftwood Beach, Calvert 

County, Maryland. (3) Left seventh costal (USNM 451945), collected by Jean Hooper from the Little Cove Point Member, St. 

Marys Formation; Chesapeake Ranch Estates, Calvert County, 

Maryland. (4) Costal fragment (CMM-V-8746), collected by Jeff 

O’Neil from the Little Cove Point Member, St. Marys Formation; Chesapeake Ranch Estates, Calvert County, Maryland. (5) 

Posterior half of neural (CMM-V-8745, part), collected by Betty 

Cridlin from the Little Cove Point Member, St. Marys Formation; Chesapeake Ranch Estates, Calvert County, Maryland. (6) 

Neural element (CMM-V-8748), collected by Robert E. Weems 

from the Little Cove Point Member, St. Marys Formation; Stratford Harbor bluffs, Westmoreland County, Virginia. (7) Distal 

costal (CMM-V-8747), collected by Walt and Nancy Johns from 

the Windmill Point Member, St. Marys Formation; Windmill 

Point, St. Mary’s County, Maryland. (8) Fragment of anterior 

central region of left hyoplastron (CMM-V-3696), collected by 

Walt Johns from the Windmill Point Member, St. Marys Formation; Windmill Point, St. Mary’s County, Maryland. (9) Proximal end of right hyoplastron (CMM-V-8752), collected by John 

R. Nance from the Windmill Point Member, St. Marys Formation; Windmill Point, St. Mary’s County, Maryland.

Description. Carapace lacks peripheral elements and 

sulcal grooves; external surface covered with a coarse, dominantly pitted texture like that of Apalone ferox and Apalone 

spinifera but unlike the fine texture of Apalone mutica; a ridge 

pattern is weakly developed along the proximal ends of costals. 

Hyoplastron has a typical Apalone conformation, with an anteroposterior length somewhat elongate as in A. ferox and longer 

than found in A. spinifera.

Remarks. Apalone spinifera occurs today in both 

Maryland and Virginia, but only in their western parts in 

streams that lie within the Mississippi River drainage basin. 

Apalone ferox does not range as far north today as Virginia or 

Maryland. Many of the specimens illustrated here are compatible in their surface texture with either A. ferox or A. spinifera, 

but not with A. mutica. The proximal hyoplastron specimen, 

however, has an anteroposterior length that is much greater 

than that of A. spinifera but does match closely that of A. ferox. 

Of the three species of Apalone presently living in the United 

FIGURE 1.4. (Opposite) Carapace elements of Kinosternidae indet. found in the Calvert Cliffs. (A) Sixth left costal (USNM 483389) in internal, 

anterior, and external views. (B) Peripheral element (CMM-V-2546) in dorsal (external) view. (C) Neural element (CMM-V-8751) in dorsal 

(top) and ventral (bottom) views. (D) Neural element (CMM-V-8750) in ventral (top) and dorsal (bottom) views. (E) Neural element (CMM-V8750) in anterior view. (F) Right hyoplastron (USNM 483389) in external (top), anterior (middle), and internal (bottom) views; arrows indicate 

the constricted region in the distal portion of the hyoplastron. (G) Tenth left peripheral (USNM 483389) in external (left), posterior (middle), 

and internal (right) views. (H) Fifth right (plastral bridge) peripheral (USNM 483389) in external (left), lateral (middle), and internal (right) 

views. (I) Third left peripheral (USNM 483389) in external (left), posterior (middle), and internal (right) views; arrow indicates the musk groove.
12 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

States, only A. ferox has been identified in the fossil record, 

ranging as far back as the Late Miocene in Florida (Hulbert, 

2001). Because of the antiquity of this material, it is possible 

that it represents a species immediately antecedent to A. ferox

that has most, but not quite all, of the osteological features 

found in A. ferox. This cannot be determined from the osteological material found to date, so the specimens described here 

are referred to Apalone cf. A. ferox in the absence of confirmatory evidence that it belongs unequivocally to the living species 

A. ferox. The occurrence of material indistinguishable from 

A. ferox in Maryland and Virginia during the Late Miocene 

suggests that the climate in Maryland and Virginia then was 

milder and/or more equable than it is today.

The surface sculpturing pattern of A. ferox is dominated 

by pits, with ridges being much less common. This pattern contrasts with the ridge-dominated surface sculpture pattern found 

in Apalone lima, which is discussed next. In the Delaware-Maryland-Virginia region to date, A. lima has been found only in the 

Calvert Formation, and A. ferox has been found only in the St. 

Marys Formation.

Apalone lima (Cope, 1869)

Trionyx lima Cope, 1869a:12 (original description).

Trionyx lima Cope, 1869b:90.

Trionyx lima Cope, 1869c:151, 153, plate vii, fig. 14.

Amyda? Lima Hay, 1908:533.

Trionychidae, genus undetermined Zug, 2001:215.

Apalone lima Weems and George, 2013:580–585.

Trionyx lima Vitek and Joyce, 2015:231.

Holotype. Fragment of the distal end of one costal.

Holotype Locality and Horizon. “Miocene 

marl,” Cumberland County, New Jersey.

Diagnosis. Carapace consists of thickened, flat costal 

elements with rounded distal edges. Dorsal surface is sculptured 

with rather high and narrow ridges running across the bone, 

separated by grooves that are somewhat wider than the ridges. 

Summits of the ridges are uneven. Connecting ridges are rare, 

but occasionally, a ridge divides or abruptly ends. Proximally, 

the ridges are somewhat irregular in their course; distally, they 

are narrow and much interrupted. Sulcal grooves are absent on 

the external surface of both the carapace and plastron.

Previously Referred Material. (1) Two carapace fragments (CMM-V-4661), collected by Ron Ison from the 

Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; 

along the Pamunkey River near the boundary between New 

Kent and King William Counties, Virginia. (2) One small carapace fragment (USNM 540752) and one left xiphiplastron fragment (USNM 540753), collected by George Simonson from the 

Cheswold sands, Fairhaven Member, Calvert Formation; Pollack 

Farm site, Kent County, Delaware (Weems and George, 2013).

Remarks. The combination of a ridge and groove 

sculpture pattern on the external surface of these elements, 

the absence of any sign of peripheral sutures on distal costal 

elements, and the absence of any indication of sulcal grooves 

all readily characterize this material as pertaining to the family Trionychidae. The costal specimens discussed here (Figure 

1.5) are thick and have a ridge and groove sculpture pattern 

indistinguishable from Apalone lima (Cope, 1869). Xiphiplastron fragments are somewhat different, having short ridge segments arranged in an irregular pattern. This species originally 

was assigned by Cope (1869) to the genus Trionyx, which 

in the nineteenth century was a catchall generic designation 

for most fossil trionychid material found in North America. 

Modern taxonomic analysis restricts the genus Trionyx to the 

African softshell turtle Trionyx triunguis (Meylan, 1987), so 

it is no longer plausible to place the species lima in that genus. 

Generic taxonomy within the family Trionychidae depends 

heavily on cranial and plastral anatomy, and none of the 

type material or the material illustrated here and ascribed to 

Apalone lima includes cranial or diagnostic plastral elements. 

Therefore, generic assignment for this taxon cannot be proven 

at this time, even though the species lima is readily recognizable. All modern softshell turtles in eastern North America are 

referable to the genus Apalone, and the living species A. ferox

has a pattern of ridges along the outer half of its mid-costals 

that is somewhat similar to that of Apalone lima. Miocene 

material from the Lee Creek Mine in North Carolina was considered by Zug (2001) to be probably (though not certainly) 

referable to Apalone. Because the Lee Creek Mine specimens 

came from the Pungo River Formation, which is identical in 

age to the lower Calvert Formation, it is likely that they also 

pertain to A. Lima. Vitek and Joyce (2015) chose to leave 

this species in the genus Trionyx as a wastebasket taxon, but 

I see no advantage to leaving this species in a genus to which 

it clearly does not belong to avoid putting it into a genus to 

which it may well belong even though that is not yet certain. 

There is no evidence to refute the assignment of this Miocene 

material to Apalone, so the species lima is referred to that 

genus until such time that any evidence comes to light demonstrating the presence of any other genus of softshell turtle 

in the Neogene or Quaternary of North America. The consistently larger size and relatively greater thickness of these 

elements, compared with similar elements of living species of 

Apalone, indicate that they pertain to a taxon larger than any 

of the living species in this genus, and therefore, they cannot 

be ascribed to any of them. Although this taxon would not be 

erected in the current taxonomic environment because of the 

sparseness of the holotype material, it is nevertheless unique, 

deeply rooted in the historic literature, and not readily confused with any other species of Apalone. For these reasons, 

this taxon is retained here despite the skepticism of Vitek 

and Joyce (2015), who considered this species to be a nomen 

dubium.
NUMBER 107 • 13

FIGURE 1.5. (A, B) Costal fragments of Apalone lima (CMM-V-4661) in dorsal (external) views. (C, D) Distal costal fragment 

of Apalone cf. A. ferox (CMM-V-3570) in dorsal (external) and lateral views. (E) Costal fragment of Apalone cf. A. ferox (CMMV-8746) in dorsal (external) view. (F, G) Left seventh costal of Apalone cf. A. ferox (USNM 451945) in dorsal (external) and 

ventral (internal) views. (H, I) Fragment of hyoplastron of Apalone cf. A. ferox (CMM-V-8752) in ventral (external) and dorsal 

(internal) views.
14 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Family Cheloniidae Oppel, 1811

Genus Trachyaspis Meyer, 1843

Turtle – Trachyaspis – Cheloniidae

Trachyaspis lardyi (illustration by Robert E. Weems)

Shell of Trachyaspis lardyi (adapted by Robert E. Weems

from Hasegawa et al., 2005)

Type Species. Trachyaspis lardyi Meyer, 1843.

Trachyaspis lardyi Meyer, 1843

Trachyaspis lardyi Meyer, 1843:699.

Testudo varicosa Costa, 1851:4. 

Chelonia varicosa Costa, 1864:12, table 1.

Chelone sp. Cope, 1867:143. 

Trachyaspis miocoenus Delfortrie, 1869:419–420, table 28, figs. 24–26. 

Trachyaspis aegyptiaca Lydekker, 1889:53, 54.

Syllomus crispatus Cope, 1896:139.

Syllomus crispatus Hay, 1908:211–212.

Trionyx bellunensis Misuri, 1911:1, 8, tables 1, 2. 

Trachyaspis bellunensis Hummel, 1932:102.

Chelonia marylandica Collins and Lynn, 1936:151, 155, 162, table 2.

Peritresius virginianus Berry and Lynn, 1936:176, table 1-4.

Kurobechelys tricarinata Shikama, 1956:37, 54, table 7, figs. 1, 2, table 8, 

figs. 1–3.

Syllomus marylandica Zangerl, 1958:40–41. 

Syllomus virginianus Zangerl, 1958:40–41, 52.

Syllomus aegyptiacus Weems, 1974:281–292.

Syllomus aegyptiacus Weems, 1980:621–625.

Syllomus aegyptiacus Zug, 2001:213.

Trachyaspis lardyi Lapparent de Broin, 2001:182.

Syllomus aegyptiacus Hasegawa et al., 2005:29–64.

Trachyaspis lardyi Chesi et al., 2007:328–321.

Trachyaspis lardyi Weems and George, 2013:570.

Trachyaspis lardyi Weems and Sanders, 2014:88.

Trachyaspis lardyi Villa and Raineri, 2015:5.

Holotype. A single well-preserved costal plate.

Holotype Locality and Horizon. Mont La 

Molière, Switzerland; upper Marine Molasse, Burdigalian, Early 

Miocene.

Diagnosis. Carapace shield shaped and flat with a 

well-developed sculptured pattern on the dorsal surface not attributable to nutrient foramina as in Lepidochelys. Sculpture 

composed of ridges and valleys; ridges irregular in middle of 

costals, trending anteroposteriorly at costal margins. Nutrient foramina are very fine and do not affect the course of the 

sculpture. Longitudinal keels on carapace variably developed, 

ranging from absent through medial keels on neurals to medial 

keels on neurals plus paralleling keels to either side on adjacent costals. All dorsal vertebral arches fused to their overlying 

neurals in adults, except the first, which is suturally attached 

throughout life. Rib necks are short. In very young individuals, peripherals probably sutured to the body of the carapace 

only by the nuchal; in older individuals, peripherals and costals 

meet suturally back at least to the eighth peripheral. Rib-free 

peripheral present between the sixth and seventh costals. At the 

posterior end of the carapace, the second suprapygal is separated from the pygal in juveniles but comes to abut against the 

pygal in older individuals, forming a posterior area of suturing 

that spreads anteriorly to include the eleventh peripherals. In 

older individuals, dorsal medial borders of the ninth and tenth 

peripherals grow inward to meet the costals and form suture 

contacts, leaving only two small fontanelles between the costals 

and the peripherals. Eight costals are always present, but eighth 

costal may split to form a supernumerary ninth costal. Eight 

neurals always present, but first occasionally is split to give the 

appearance of nine neurals. Two intercostal postneurals always 

present; a third appears if the eighth costal has an extra rib 

head or is split. Suprapygals lie entirely behind the last (eighth 
NUMBER 107 • 15

or ninth) costals. Normal pattern of five vertebral scutes (six if 

an extra postneural is present) and four pleural scutes; vertebral scutes twice as long as wide. 

Plastron moderately reduced, left and right sides not suturally attached. Epiplastra large and expanded, entoplastron very 

narrow but elongate. The hyoplastra and hypoplastra rather 

rectangular in shape and sharply angled about one-third of the 

way from their internal borders to their external borders; hyoplastra and hypoplastra meet suturally along nearly their entire 

common border. Xiphiplastra wide, separated by only a narrow 

fontanelle. Plastron sparingly sculptured; sculpture obscure anteriorly. Plastral sulci are best seen in juveniles. 

Pelvic girdle has a large ischial spine, and the femur has large 

and elevated trochanters. The humerus has its deltopectoral crest 

located far down the shaft. Skull and jaws have a pseudodont 

dentition pattern on the jaws functionally acting as teeth. Dorsal 

surface of skull has a pattern reminiscent of the carapace surface 

pattern but finer.

Previously Referred Material from the Chesapeake Group. (1) Partial carapace (USNM 13859, holotype of Peritresius virginianus Berry and Lynn) including neurals 1 

and 5–6, suprapygal 1, right costals 1–5 and 8, three peripherals, 

plus plastron including part of left hyoplastron, both hyoplastra, 

right xiphiplastron, two dorsal vertebral centra, cervicals 6 and 8, 

collected by W. G. Lynn from Plum Point Member, Calvert Formation; Horsehead Cliffs, Westmoreland State Park, Westmoreland 

County, Virginia. (2) Partial carapace (USNM 24872) with nuchal 

fragment, all neurals and postneurals, portions of all costals, right 

peripherals 1 and 2, plus partial plastron including a hypoplastron, 

one dorsal vertebral centrum, cervical 8, portions of both ilia, both 

ischia, a fragment of the left pubis, proximal end of right femur, 

collected by T. B. Ruhoff from a shelf of marl exposed at low tide, 

upper SZ 11, Plum Point Member, Calvert Formation; 0.8 km (0.5 

mile) south of Parkers Creek, Calvert County, Maryland. (3) Right 

humerus (USNM 24878), collected by R. Lee Collins from SZ 12, 

Plum Point Member, Calvert Formation; 0.8 km (0.5 mile) south 

of Parkers Creek, Calvert County, Maryland. (4) Central carapace 

region (USNM 13825) comprising neurals 2–4, both third and 

fourth costals, right peripherals 4 and 5, and left peripherals 4–6, 

holotype of Chelonia marylandica (Collins and Lynn), collected by 

R. Lee Collins and W. Gardner Lynn from base of SZ 10, lower 

Plum Point Member, Calvert Formation; 3.7 km (2.3 miles) south 

of Chesapeake Beach, Calvert County, Maryland. (5) Humerus and 

two costal fragments (AMNH 6134, holotype of Syllomus crispatus

Cope), Plum Point Member, Calvert Formation; from marl pits near 

Hanover, Hanover County, Virginia. (6) Carapace (AMNH 1661, 

paratype of Syllomus crispatus Cope) including nuchal, neurals 1–7, 

postneural 3, suprapygals 1 and 2 pygal, portions of all costals, right 

peripherals 1, 2, and 11, left peripherals 1–6 and 11, plus plastron 

including both xiphiplastra and both hypoplastra, right and left 

scapulae, right and left coracoid, parts of right and left pubes and 

right and left ischia, one dorsal vertebral centrum, cervicals 6 and 

7, fragmentary parietal, collected by Charles T. Berry, Plum Point 

Member, Calvert Formation; Horsehead Cliffs, Westmoreland 

County, Virginia. (7) Carapace (USNM 13858, paratype of Peritresius virginianus Berry and Lynn) with neurals 2–7, right costals 2–8, 

left costals 3–7, collected by W. Gardner Lynn, upper Plum Point 

Member, Calvert Formation; Horsehead Cliffs, Westmoreland State 

Park, Westmoreland County, Virginia. (8) Partial carapace (USNM 

24870) including nuchal; neurals 1, 2, 4, and 7; postneurals 1–3; 

suprapygals 1 and 2; pygal; parts of all right costals; parts of left 

costals 1–3, 7, and 8; right peripherals 4–7 and 10–11; left peripheral 2, plus partial plastron including parts of both hypoplastra and 

xiphiplastra, three dorsal vertebral centra, three caudal vertebrae, 

left ischium, both ilia, right femur, collected by Robert A. Graham 

and Robert E. Weems from near the top of SZ 15A, 60 cm (2 feet) 

below base of SZ 15B (see Weems et al., 2017, for revised zonation); near middle of Stratford Cliffs, Stratford Hall, Westmoreland 

County, Virginia. (9) Posterior carapace (USNM 24871) including 

neurals 6 and 7, postneurals 1–3, suprapygals 1 and 2, pygal, right 

costals 4–9, left costals 4 and 6–9, left peripheral 1, right peripheral 

1, left xiphiplastron, left coracoid, collected by Robert E. Weems 

from near the top of SZ 15A, 0.3 m (1 foot) below base of SZ 

15B (see Weems et al., 2017, for revised zonation); eastern Stratford Cliffs, Stratford Hall, Westmoreland County, Virginia. (10) 

Partial carapace (USNM 24873) including neurals 4–6, left costals 

2–8, left peripherals 4–11, collected by Robert E. Weems from the 

basal foot of SZ 15B (see Weems et al., 2017, for revised zonation); about 1.3 m (4 feet) above beach, eastern Stratford Cliffs, 

Stratford Hall, Westmoreland County, Virginia. (11) Anterior carapace (USNM 24874) with part of nuchal, neurals 1a and 1b, left 

costals 1–3, peripherals 2–6, collected by Robert E. Weems from 

the basal foot of SZ 15B (see Weems et al., 2017, for revised zonation); about 1.2 m (4 feet) above beach, eastern Stratford Cliffs, 

Stratford Hall, Westmoreland County, Virginia. (12) Posterior carapace (USNM 16742) including neural 7, postneurals 1–3, suprapygal 1, right and left costals 6–8, collected by Richard Lemke from 

upper Plum Point Member, Calvert Formation; 0.8 km (0.5 mile) 

south of Scientists Cliffs, Calvert County, Maryland. (13) Partial 

carapace (USNM 24876) including neurals 2 and 7, postneural 1, 

parts of right costals 1–6, collected by Robert E. Weems from the 

basal foot of SZ 15B (see Weems et al., 2017, for revised zonation); 

about 1.2 m (4 feet) above beach, eastern Stratford Cliffs, Stratford 

Hall, Westmoreland County, Virginia. (14) Partial plastron (USNM 

20375) including right xiphiplastron and most of right hypoplastron, collected by R. Lee Collins from upper Plum Point Member, 

Calvert Formation; Horsehead Cliffs, Westmoreland State Park, 

Westmoreland County, Virginia. (15) Nuchal and distal portion of 

humerus (USNM 24879), collected by Albert C. Myrick Jr. from 

SZ 11, Plum Point Member, Calvert Formation; approximately 

230 m (250 yards) south of Parkers Creek, Calvert County, Maryland. (16) Limb elements (USNM 24880) including left and right 

humeri, left radius, left ulna, three carpals, collected by Robert E. 

Weems from fallen block from SZ 15B (see Weems et al., 2017, 

for revised zonation); Horsehead Cliffs, Westmoreland State Park, 

Westmoreland County, Virginia. (17) Left femur (USNM 24881), 

collected by Robert E. Weems from the basal foot of SZ 15B (see 

Weems et al., 2017, for revised zonation); about 1.2 m (4 feet) 
16 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

above beach, eastern Stratford Cliffs, Stratford Hall, Westmoreland 

County, Virginia. (18) Right humerus (USNM 24882), collected by 

Albert C. Myrick Jr. from SZ 15B (see Weems et al., 2017, for revised zonation); about 4.5 m (15 feet) above beach, Stratford Cliffs, 

Stratford Hall, Westmoreland County, Virginia (Weems, 1974). 

(19) Largely complete skull and dentary (USNM 187382) associated with a fragmentary carapace and a humerus, collected by Albert C. Myrick Jr. from SZ 10 (see Weems et al., 2017, for revised 

zonation); bluffs on the Morris property along the right (south) 

bank of the Potomac River, 1 km (0.62 mile) west of the mouth of 

Bridge’s Creek, Wakefield, Westmoreland County, Virginia (Weems, 

1980). (20) Fused dentaries (USNM 427790), collected by Al Robb 

from Sunken Meadow Member, Yorktown Formation; Lee Creek 

Mine near Aurora, Beaufort County, North Carolina (Zug, 2001).

Newly Referred Material. (1) Partial carapace 

(CMM-V-243) with neural lacking a ridge, collected by Norman 

L. Riker, Calvin Taylor, and David J. Bohaska from Popes Creek 

Sand Bed, Fairhaven Member, Calvert Formation; south of Popes 

Creek, Charles County, Maryland. (2) Left hyoplastron and hypoplastron (CMM-V-572), collected by Derek Yoast from fallen 

block of SZ 17, Drumcliff Member, Choptank Formation; about 

1.5 km (0.93 mile) north of Matoaka Beach, Calvert County, 

Maryland. (3) Fifth neural element (CMM-V-5913), collected by 

John R. Nance from Little Cove Point Member, St. Marys Formation; Chesapeake Ranch Estates north of Driftwood Beach, 

Calvert County, Maryland. (4) Proximal end of sixth right costal (CMM-V-3115), collected by William “Bill” Counterman 

from beach, Little Cove Point Member, St. Marys Formation; 

between Chesapeake Ranch Estates and Driftwood Beach, Calvert County, Maryland. (5) Peripheral element (USNM 466115), 

collected by David “Dave” J. Bohaska from the Little Cove Point 

Member, St. Marys Formation; Chesapeake Ranch Estates north 

of Driftwood Beach, Calvert County, Maryland. (6) Proximal 

end of left costal (CMM-V-8727), collected by John R. Nance 

from Little Cove Point Member, St. Marys Formation; Chesapeake Ranch Estates, Calvert County, Maryland. (7) Ninth right 

peripheral (CMM-V-2978), collected by Stephen J. Godfrey from 

beach, Windmill Point Member, St. Marys Formation; Windmill Point, St. Mary’s County, Maryland. (8) Right humerus 

(CMM-V-9975), collected by Aaron A. Alford from the Eastover 

Formation; right bank of the Pamunkey River, New Kent 

County, Virginia.

Remarks. Material belonging to this species has been 

described under three different names in the Maryland-Virginia region: Syllomus crispatus Cope, 1896; Chelonia marylandica Collins and Lynn, 1936; and Peritresius virginianus Berry and Lynn, 

1936. Weems (1974) recognized that all of this material represented individual variation within a single fossil sea turtle taxon 

and designated this species as Syllomus aegyptiacus on the basis 

of advice that the type material of Trachyaspis lardyi belonged to 

a dermatemydid turtle and not to a sea turtle. Lapparent de Broin 

(2001) rejected the conclusion that Trachyaspis was a dermatemydid turtle and concluded instead that it was a cheloniid. Chesi et 

al. (2007) studied new material from Italy referable to Trachyaspis 

lardyi and agreed that this taxon clearly represents a cheloniid sea 

turtle. Therefore, the oldest valid name for the Calvert Formation 

material is Trachyaspis lardyi and not Syllomus aegyptiacus, and 

Weems and George (2013) and Weems and Sanders (2014) have 

concurred with this conclusion. The carapace and plastron surface 

pattern, consisting of raised areas of bumps and elongate vermiform ridges, is distinctive and makes this turtle exceptionally easy 

to identify. The pattern is somewhat reminiscent of that found on 

the carapace and plastron of the softshell turtle Apalone, but close 

examination shows that the patterns are not identical and are 

readily differentiated from each other. Trachyaspis lardyi is by far 

the most commonly found turtle in the Calvert, Choptank, and St. 

Marys Formations. More than 80 specimens, ranging from single 

elements to largely complete turtle shells, have been cataloged into 

the Smithsonian and CMM collections (Figure 1.6). Except for 

SZs 1–3A, which comprise the lowest part of the Fairhaven Member and to date have yielded no reptile, bird, or mammal remains, 

Trachyaspis has been found throughout the Calvert, Choptank, 

St. Marys, and Eastover Formations. This species also ranges upward into the Early Pliocene Sunken Meadow Member of the Yorktown Formation in North Carolina (Zug, 2001) and has been 

reported from the Late Pliocene of Italy (Villa and Raineri, 2015). 

Trachyaspis has a global Northern Hemisphere distribution, being 

reported from Europe, Egypt, Japan, and the eastern United States 

(Chesi et al., 2007). Even so, it has not been reported from the 

Miocene or Pliocene of Florida (Hulbert, 2001), which suggests 

that it did not range as far south as Florida during the Miocene 

and Pliocene. This range may indicate that Trachyaspis spread between the northern Pacific Ocean and the northern Atlantic Ocean 

by way of an ice-free Miocene Arctic Ocean.

FIGURE 1.6. (Opposite) Skeletal elements of Trachyaspis lardyi. (A) Left hyoplastron and hypoplastron (CMM-V-572) in ventral (external) 

view. (B) Partial carapace (USNM 24872) in dorsal (external) view with sulcal grooves enhanced for clarity; note the large tumorous bony mass 

between neural 5 and right costal 4. (C) Fifth neural element (CMM-V-5913) in dorsal (external) view. (D, E) Caudal vertebra in left lateral 

and anterior views, respectively. (F) Right hypoplastron and xiphiplastron (USNM 13859) in ventral (external) view. (G) Right femur (USNM 

24870) in anterior view. (H, I) Subadult right humerus (USNM 24878) in ventral (internal) and dorsal (external) views. (J) Proximal end of 

right sixth costal (CMM-V-3115). (K–M) Ninth right peripheral (CMM-V-2978) in dorsal, anterior, and ventral views. (N) Central portion of 

“Chelonia marylandica” carapace (USNM 13825) with sulcal grooves enhanced for clarity.
NUMBER 107 • 17
18 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Trachyaspis had a greatly modified humerus that provided 

exceptional forelimb power; an enlarged ischial spine, indicating exceptional pelvic muscular control for a cheloniid turtle; 

and jaws that were sharply crenulated to create a pseudodont, 

or “false-toothed,” appearance (Figure 1.7). It is quite possible 

that all of these features were adaptations for an active and predaceous lifestyle. It is remarkable that there also is a pseudodont 

bird (the giant pelicaniform Pelagornis) that occurs in the same 

beds. Possibly, both animals hunted the same food, which may 

have been some kind of cuttlefish.

Carapace specimens from the Calvert and Choptank Formations show considerable variability in keel development, 

but the few carapace specimens known from the St. Marys and 

Yorktown Formations are entirely keeled. I suspect that this reflects a taxonomically significant difference between the CalvertChoptank Trachyaspis populations and the St. Marys–Yorktown 

Trachyaspis populations, but the material from the younger 

group of formations is currently too sparse to justify applying a 

new species name to this group. It is also entirely possible that 

the changes in Trachyaspis seen through time will prove to represent a continuous gradation (morphocline) not readily divisible into discretely separate species. Resolution of this interesting 

problem will require more complete Late Miocene and Pliocene 

material. The best skull and plastron materials have been recovered from Japan (Hasegawa et al., 2005), and the reader is encouraged to consult that reference for more pictures of diverse 

skeletal elements of this species.

Genus Procolpochelys (Hay, 1908)

Turtle – Procolpochelys – Cheloniidae

Shell of Procolpochelys sp. (adapted by REW 

from Weems and Brown, 2017)

Type Species. Procolpochelys grandaeva (Leidy, 1851).

Procolpochelys grandaeva (Leidy, 1851)

Chelonia grandaeva Leidy, 1851:329 (original description).

Procolpochelys grandaeva Hay, 1908:216–220.

Procolpochelys grandaeva Zangerl and Turnbull, 1955:345–382.

Procolpochelys grandaeva Weems, 1974:293–299.

Procolpochelys grandaeva Spamer et al., 1995:125.

Procolpochelys sp. Zug, 2001:213.

Procolpochelys grandaeva Weems and Sanders, 2014:88.

Procolpochelys grandaeva Weems and Brown, 2017:1228–1243.

Holotype. Three neural plates (ANSP 9210–9212) 

from one locality but not certainly from one individual.

Holotype Locality and Horizon. Miocene 

Marl of Salem County, New Jersey.

Diagnosis. Large cheloniid turtle with carapace up to 1.5 

m (5 feet) long. Neurals 2–6 often are divided into front and back 

portions, with neural arches of thoracic vertebrae attached to the 

smaller posterior part of each split neural. Costals are laterally compressed but anteroposteriorly expanded, lacking surface sculpture 

and possessing only faintly impressed sulcal grooves marking the 

borders of dermal scutes; carapace surface smooth without raised 

longitudinal ridges; juveniles have relatively thin costals (about 5 

mm thick), but with advancing age costals thicken greatly (up to 20 

mm thick); costoperipheral fontanelles large, even in adults. Plastron strongly reduced, becoming increasingly so with advancing 

age. Humerus most similar to Caretta among living cheloniids, with 

lateral tubercle short and wide, dorsomedial muscle scar round and 

shallow, and the deltopectoral crest quite prominent and coalesced. 

Snout of Procolpochelys grandaeva is short and rather pointed; in 

ventral view, the foramina orbito-nasale are relatively large, and the 

pterygoids are correlatively quite narrow.

Previously Referred Material. (1) Carapace 

(USNM 24889) including nuchal; split neurals 1b, 2a, 2b, 3a, 3b, 

4a, and 5a; parts of left costals 1–6; right costals 1–6 and 8; fragment of suprapygal; and first right peripheral, collected by Robert 

A. Graham and Robert E. Weems, upper SZ 15A, about 0.3 m (1 

foot) below base of SZ 15B (Weems et al., 2017), Plum Point Member, Calvert Formation; western end of Horsehead Cliffs about 1.5 

m (5 feet) above beach, Westmoreland State Park, Westmoreland 

County, Virginia. (2) Carapace fragment (USNM 24888) including 

split neurals 6b, 6a, 7b, 8a, and 8b; suprapygal; pygal; left costals 

FIGURE 1.7. (Opposite) (A, B) Right humerus of adult Trachyaspis lardyi (CMM-V-9975) in ventral (internal) and dorsal (external) views. 

(C) Partial skull of Procolpochelys grandaeva (USNM 358862) in dorsal view. (D) Skull cap of T. lardyi (USNM 187382) in dorsal view. (E) 

Right dentary of P. grandaeva (USNM 442385) in lateral view. (F) Fused dentaries of P. grandaeva (USNM 442385) in dorsal view. (G) Fused 

dentaries of T. lardyi (USNM 427790) in dorsal view. (H) Lateral view of right dentary of T. lardyi (USNM 187382) showing pseudodont 

dentition.
NUMBER 107 • 19
2 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

1–8; portions of right costals 5–8; left peripherals 1, 3–9, and 11, 

plus left hyoplastron, left hypoplastron, left xiphiplastron, left 

quadrate basioccipital, right opisthotic, part of left parietal, left humerus, four metacarpals, two phalanges, right ilium, and left femur, 

collected by albert C. Myrick Jr., John S. Moses, and Robert E. 

Weems from upper SZ 15A, about 0.3 m (1 foot) below base of SZ 

15B (Weems et al., 2017), Plum Point Member, Calvert Formation; 

eastern end of Stratford Cliffs, 15.24 cm (0.5 foot) above beach, 

Stratford Hall, Westmoreland County, Virginia. (3) Neural element 

(USNM 1184), collected by R. Lee Collins from the Popes Creek 

Sand Bed, Fairhaven Member, Calvert Formation; near the Pamunkey River in the region where it flows between New Kent and 

King William Counties, Virginia. (4) Basicranium (USNM 186969) 

consisting of right quadrate, right opisthotic, parts of right and left 

parietals, supraoccipital, basioccipital, and left exoccipital, collected 

by D. B. Mackie from the upper Plum Point Member, Calvert Formation; Governor Run, Calvert County, Maryland (Weems, 1974). 

(5) Partial skull (USNM 358862) including most of left side (except 

squamosal) and entire basicranium region, collected by Robert E. 

Weems from the Popes Creek Sand Bed, Fairhaven Member, Calvert 

Formation; bluffs south of Popes Creek Maryland, Charles County, 

Maryland (Weems and Sanders, 2014).

Newly Referred Material. (1) Left hyoplastron 

and hypoplastron (CMM-V-8769), found by Kyle Grimsley in the 

Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; in 

bluffs south of Popes Creek, Charles County, Maryland. (2) Fifth 

cervical vertebra (CMM-V-8772), collected by Kyle Grimsley from 

the Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; 

in bluffs south of Popes Creek, Charles County, Maryland. (3) Interneural element (CMM-V-8771), collected by Gary Grimsley 

from the Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; in bluffs south of Popes Creek, Charles County, Maryland. 

(4) Left epiplastron (CMM-V-8775), collected by Kyle Grimsley 

from the Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; in bluffs south of Popes Creek, Charles County, Maryland. 

(5) Suprapygal (CMM-V-8770), collected by Kyle Grimsley from 

the Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; in bluffs south of Popes Creek, Charles County, Maryland. 

(6) Pygal (CMM-V-8408), collected by Daryl Domning from the 

Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; in 

bluffs south of Popes Creek, Charles County, Maryland. (7) Partial 

carapace (CMM-V-5956) including part of neural 4; posterior half 

of neural 7; all of neural 8; proximal parts of right costals 2 and 3; 

right costals 5–6; parts of right costal 7; most of left costals 3, 6, 7, 

and 8; first suprapygal; and proximal end of a coracoid, collected 

by Ron Ison from the Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; right (south) bank of the Pamunkey River, 

New Kent County, Virginia. (8) Fused dentaries (USNM 442385), 

collected on beach by George Fonger, probably from SZ 10, 11, 

or 12, Plum Point Member, Calvert Formation; Plum Point, Calvert County, Maryland. (9) Neural element (USNM 358021), 

collected by George Fonger, SZ 12, Plum Point Member, Calvert 

Formation; south of Plum Point, Calvert County, Maryland. (10) 

Right second costal (CMM-V-83), collected by Norman L. Riker, 

from SZ 19, Boston Cliffs Member, Choptank Formation; Camp 

Conoy-Moran’s, 0.8 km (0.5 mile) south of beach. (11) Proximal 

fifth right costal fragment (CMM-V-2328), collector unlisted, 

found on beach, Little Cove Point Member, St. Marys Formation; 

Chesapeake Ranch Estates, Calvert County, Maryland. (12) Costal fragment (CMM-V-4090), collected by John R. Nance, Little 

Cove Point Member, St. Marys Formation; Chesapeake Ranch Estates, Calvert County, Maryland. (13) Humerus (CMM-V-4571), 

collected by John R. Nance on beach, Little Cove Point Member, 

St. Marys Formation; Chesapeake Ranch Estates, Calvert County, 

Maryland. (14) Peripheral element (CMM-V-5365), collected on 

beach by David “Dave” J. Bohaska, Little Cove Point Member, 

St. Marys Formation; Chesapeake Ranch Estates, Calvert County, 

Maryland. (15) Undivided neural element (CMM-V-8726), collected by John R. Nance on beach, Little Cove Point Member, St. 

Marys Formation; Chesapeake Ranch Estates, Driftwood Beach, 

Calvert County, Maryland.Remarks. Procolpochelys grandaeva is the second most commonly found turtle in the Calvert, 

Choptank, and St. Marys Formations. Twenty specimens, ranging 

from single elements to largely complete turtle shells, have been 

cataloged into the Smithsonian and CMM collections from Maryland and Virginia. Specimens of Procolpochelys grandaeva occur 

at the Lee Creek Mine, but only rarely; they apparently came from 

the Miocene Pungo River Formation, which is age equivalent to 

the lower Calvert Formation (Zug, 2001). Interestingly, no specimens of Procolpochelys have been reported from the Miocene 

strata of Florida (Hulbert, 2001). The split neurals in this species 

are quite distinctive, with the posterior (smaller) neural part attached to an underlying vertebral centrum (Figure 1.8O,P) and 

the anterior (larger) part lacking a ventral attachment to an underlying bone (Figure 1.8M,N). Because of this arrangement, the 

proximal end of most costals (but not all) has a well-developed but 

shallow notch marking the border of the true neural elements between the interneurals (Figure 1.8A). Remains of Procolpochelys 

FIGURE 1.8. (Opposite) Skeletal elements of Procolpochelys grandaeva. (A) Right second costal (CMM-V-83) showing notch (arrow) bordering the true neural element. (B, C) Proximal costal of partially grown individual (CMM-V-2328) showing relatively thin costal thickness. (D, E) 

Costal fragment of adult individual (CMM-V-4090) showing much greater relative thickness. (F) Left femur (USNM 24888) in anterior view. 

(G, H) Right humerus (CMM-V-4571) in dorsal and anterior views. (I, J) Peripheral element (CMM-V-5365) in dorsal and internal views. (K) 

Left hyoplastron and hypoplastron (CMM-V-8769) in ventral (external) view. (L) Fifth cervical vertebra (CMM-V-8772) in ventral view. (M, 

N) Interneural element (CMM-V-8771) in dorsal and ventral views. (O, P) Neural element (CMM-V-8726) in dorsal and ventral views.
NUMBER 107 • 21
2 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

grandaeva are much less common than remains of the smaller sea 

turtle Trachyaspis lardyi but more common than remains of the 

largest sea turtle, Psephophorus polygonus. This relative fossil 

abundance probably reflects the real relative abundance of these 

three species because smaller animals tend to be more numerically 

abundant than larger animals in most environmental settings. Procolpochelys grandaeva, although a pancheloniid turtle, is not particularly closely related to any of the crown cheloniid sea turtles 

living today (Weems and Brown, 2017).

The carapace of a half-grown specimen of P. grandaeva

(CMM-V-5956) has the same proportions as adult carapaces of 

this species (Figure 1.9), but its carapace is much thinner, indicating that toward maturity the carapace of P. grandaeva thickens 

greatly. The distinctly different morphology of these carapace elements from those of Procolpochelys melii precludes reference of 

this specimen to P. melii.

Cheloniidae gen. et sp. indet.

Referred Material. (1) Left epiplastron (CMMV-8774), collected by Kyle Grimsley from the Popes Creek 

Sand Bed, Fairhaven Member, Calvert Formation; in bluffs 

south of Popes Creek, Charles County, Maryland. (2) Third 

neural (CMM-V-8883), collected by Kyle Grimsley from the 

Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; 

in bluffs south of Popes Creek, Charles County, Maryland. (3) 

Pygal element (CMM-V-8953), collected by Steven Jasinski from 

SZ 8, Plum Point Member, Calvert Formation; in bluffs south of 

Chesapeake Beach, Calvert County, Maryland.

Remarks. The neural element (Figure 1.10C) is comparable in size to the neurals of adult Procolpochelys grandaeva but 

is much thinner, which precludes assignment of this specimen to 

that species. This neural also is too large and too smooth to be assigned to Trachyaspis lardyi. The epiplastron (Figure 1.10B) is much 

thicker and more massive than the comparable element in Procolpochelys grandaeva (Figure 1.10A) and Procolpochelys charlestonensis

(Weems and Sanders, 2014: supplementary data, fig. S6B); it also is 

much rounder than the flattened and relatively much wider epiplastra of Trachyaspis lardyi (see life rendering illustration in heading 

for T. lardyi in this chapter). Assuming that both of these elements 

belonged to a single kind of cheloniid sea turtle, it was moderately 

large with a carapace slightly less than 1.0 m (3 feet) long, had hexagonally shaped unkeeled neurals lacking surface sculpture, and 

had a plastron that was strongly reduced with epiplastra relatively 

much wider and more massive than in Procolpochelys charlestonensis or Procolpochelys grandaeva. The pygal element (Figure 1.10D) 

is deeply notched posteriorly, quite unlike either Procolpochelys or 

Trachyaspis; it appears to belong to an animal that was about half 

the size of the animals that possessed the other two elements. It is 

assumed that this pygal represents a young individual of the same 

indeterminate cheloniid species as the other two elements discussed 

here, but it is entirely possible that it belongs to a second indeterminate cheloniid species. All of this material has come only from the 

older (Burdigalian) part of the Calvert Formation.

These shell and girdle elements almost certainly came from 

cheloniid turtles, but none of them falls within the definition of P.

grandaeva or T. lardyi. Searching beyond the Atlantic Seaboard 

region, these elements also cannot be assigned to either of the two 

European Miocene cheloniid turtles that have been described: 

“Chelonia” girundica Delfortrie, 1869 and Procolpochelys melii

(Misuri, 1910). The type material of “Chelonia” girundica (Figure 

1.11) does not include a third neural, but it does include a right 

epiplastron (Delfortrie, 1869: plate 25, fig. 1a) that is somewhat 

similar to that of Lepidochelys olivacea but not at all like the epiplastron illustrated here (Figure 1.10B). Similarly, the pygal looks 

nothing like the pygal of “Chelonia” girundica.

Assignment of “Chelonia” girundica to Chelonia seems very 

unlikely. When the type material of “Chelonia” girundica is compared to similar elements of Lepidochelys olivacea and Chelonia 

mydas, it can be seen that the posterior carapace elements are reminiscent of the comparable elements of C. mydas, but the more anterior carapace elements are more similar to those of L. olivacea

(Figure 1.11). “Chelonia” girundica lacks two very important synapomorphies found in L. olivacea and Caretta caretta: a strong 

tendency for the neurals to split into smaller parts and the presence of a supernumerary anterior pleural scute overlying the first 

costal and nuchal elements. In these regards, “C.” girundica can 

be excluded from the definition of “Tribus Carettini” of Zangerl 

and Turnbull (1955) and falls within the definition of their “Tribus 

Chelonini.” At the same time, however, the strongly reduced first 

costals and strongly elongate fourth costals of “Chelonia” girundica

are not at all like the first or fourth costals of Chelonia mydas, and 

the neural scutes of “C.” girundica are shaped more like those of 

Lepidochelys and Caretta than they are like the neural scutes of C. 

mydas. It seems likely that “C.” girundica, when better known, will 

be assigned to its own genus within the family Cheloniidae.

Assignment to Procolpochelys melii cannot be supported because the epiplastron of this undescribed new Calvert cheloniid is 

very different in shape and massiveness from the epiplastra known 

in the two species of Procolpochelys (Figure 1.10A,B). The size 

and shape of the third neural elements are similar, but this is a 

rather common characteristic of many species of cheloniid turtles. 

Thus, although the material assigned to this new unnamed cheloniid taxon cannot be rigorously excluded from assignment to 

Procolpochelys melii, nothing of a positive nature supports such 

an assignment. For now, this sparse but tantalizing Calvert cheloniid material must be considered to be generically and specifically 

indeterminate but at the same time not referable to any described 

genus or species of Miocene cheloniid turtle. This indeterminate 

Calvert sea turtle, known only from the Popes Creek Sand Bed 

at one locality and from the lower Plum Point SZ 8 bed of the 

Calvert Formation, probably was normally an inhabitant of tropical waters south of the Salisbury Embayment during early Middle 

Miocene times and only rarely migrated north into this region. 

During the early Middle Miocene, it is likely that the ancestors 

of modern cheloniid genera inhabited the Indo-Pacific region and 

were only occasional visitors to the northwestern Atlantic region 

until Late Miocene or Pliocene time (Weems and Brown, 2017).
FIGURE 1.9. An adult Procolpochelys grandaeva carapace (modified from Zangerl and Turnbull, 1955; top) 

and the half-grown Procolpochelys grandaeva carapace from the Calvert Formation (CMM-V-5956; bottom 

left). The carapace of Procolpochelys melii is shown for comparison (bottom right).

NUMBER 107 • 2 3
2 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 1.10. Skeletal elements of Procolpochelys grandaeva and one or more indeterminate cheloniid species. (A) Left epiplastron of P. grandaeva (CMM-V-8775). (B) Left epiplastron of an indeterminate cheloniid (CMM-V-8774). (C) Third neural 

element of an indeterminate cheloniid in dorsal (top left), ventral (bottom), and lateral (top right) views (CMM-V-8883). (D) 

Pygal of an indeterminate cheloniid in dorsal view (CMM-V-8953).
NUMBER 107 • 2 5

FIGURE 1.11. Carapaces of selected cheloniid turtles in dorsal view: Lepidochelys olivacea (adapted from Zangerl and 

Turnbull, 1955), Chelonia mydas (adapted from Zangerl, 1958), and approximate restoration of the carapace of the Miocene cheloniid turtle “Chelonia” girundica (constructed from carapace elements illustrated in Delfortrie, 1869).
2 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Genus Lepidochelys (Fitzinger, 1843)

Turtle – Lepidochelys – Cheloniidae

Lepidochelys sp. (illustration by Brenna Litynski)

Shell of Lepidochelys kempii

Type Species. Lepidochelys olivacea (Eschscholtz, 1829).

Lepidochelys cf. L. kempii

Referred Material. (1) Fifth left costal (USNM 

639757), collected by David “Dave” J. Bohaska from fallen block 

of the Little Cove Point Member; north of Driftwood Beach and 0.8 

km (0.5 mile) south of Little Cove Point, Calvert County, Maryland. (2) Tenth right peripheral (CMM-V-8754), found by John R. 

Nance from the Little Cove Point Member of the St. Marys Formation; Driftwood Beach, Calvert County, Maryland.

Remarks. The fifth costal (Figure 1.12C,D) from the 

Little Cove Point Member of the St. Marys Formation assigned 

to this genus is far too thick to belong to Trachyaspis lardyi, 

is too elongate to belong to Procolpochelys grandaeva, has sulcal grooves indicating a neural scute narrower than that found 

in Procolpochelys grandaeva or Procolpochelys melii, and lacks 

the dense and smooth external surface typical of Procolpochelys 

grandaeva. Instead, it has a finely grooved external surface that 

is unlike that of Trachyaspis lardyi but rather is indistinguishable 

from the external surface of costals in modern specimens of Lepidochelys. This costal from the St. Marys Formation is much less 

elongate than the fifth costals of the living species Lepidochelys 

olivacea but is indistinguishable in its proportions from the living 

species Lepidochelys kempii, and for this reason it is tentatively 

attributed to L. kempii. The other specimen from the Little Cove 

Point Member referable to L. kempii is a tenth right peripheral 

(Figure 1.12A,B) that has a large, deep, rounded socket to receive 

a robust costal rib and an external surface texture similar to that 

of the fifth costal and comes from a turtle about the same size as 

the turtle from which the fifth costal came. The collecting locality 

for these two specimens is the same, which raises the possibility 

that the two specimens may have come from a single individual. 

The age of the Little Cove Point Member, about 10 Ma, makes 

it plausible that this material might pertain to an antecedent species of Lepidochelys kempii now extinct. However, until such 

time as more complete material can support the existence of such 

an undescribed species antecedent to Lepidochelys kempii, this 

St. Marys material is referred to the living species with which it 

is entirely comparable. The only other documented occurrences 

of Lepidochelys in the eastern United States are from the Early 

Pliocene Sunken Meadow Member of the Yorktown Formation 

at the Lee Creek Mine in North Carolina (Zug, 2001) and from 

the Early Pliocene Bone Valley Formation of Florida (Dodd and 

Morgan, 1992).

Family Dermochelyidae Fitzinger, 1843

Genus Psephophorus Meyer, 1847

Turtle – Dermochelys – Dermochelyidae

Dermochelys coriacea (illustration by Tim Scheirer)

Type Species. Psephophorus polygonus Meyer, 1847.
NUMBER 107 • 2 7

Psephophorus polygonus Meyer, 1847

Psephophorus polygonus Meyer, 1847:572–581.

Psephophorus calvertensis Palmer, 1908:369–373.

Psephophorus calvertensis Weems, 1974:301–302.

“Psephophorus” calvertensis Wood et al., 1996:282–285.

Psephophorus polygonus? Delfino et al., 2013:14.

Neotype. A slab containing articulated ridge and nonridge ossicles from part of a dermochelyid dermal shield (NHMW 

2011/0330/0001) displayed at the Naturhistorisches Museum Wien 

(Vienna). The location of the holotype is unknown and may be lost; 

the neotype is a fragment of the same carapace as the holotype that 

fit together with the holotype fragment (Wood et al., 1996).

Holotype Horizon and Locality. Sandburg 

Member of the Studienka Formation, Middle Miocene; upper 

layers of Sandburg Hill, Devínska Nová Ves, close to Bratislava, 

Slovakia.

Diagnosis. On the basis of the following combination of characters (adapted from Delfino et al., 2013), P. polygonus differs from other dermochelyid turtles possessing an 

“epithecal” shield formed by numerous small bony ossicles: 

thick ossicles; ossicles not greatly varying in size and shape; 

ossicles edges with reduced sutural structures; ossicles not arranged in the “sunflower” pattern typical of Natemys; largest 

ossicles arranged in several longitudinal ridges, dorsally arched 

in cross section and often viscerally flat (i.e., ridge is expressed 

only on the dorsal surface), although sometimes viscerally concave (i.e., the ridge curvature is also expressed on the visceral 

surface) and tectiform in cross section; ridge ossicles characterized by variable thicknesses but lacking true external keels like 

those present in Dermochelys; “peaks and valleys” are present 

along the longitudinal ridges, with peaks and bottoms of the 

valleys corresponding to ossicle suture boundaries; neighboring 

longitudinal ridges separated by at least five and often many 

more than five ossicles. 

FIGURE 1.12. Carapace elements of Lepidochelys cf. L. kempii from the Little Cove Point Member of the St. Marys Formation, 

Calvert Cliffs. (A, B) Tenth right peripheral (CMM-V-8754) in external and internal views and (C, D) fifth left costal (USNM 

639757) in medial and dorsal views.
Previously Referred Material. (1) Holotype 

specimen of Psephophorus calvertensis (USNM 6059) consisting of patches of dorsal dermal shield ossicles and numerous 

isolated ossicles, originally articulated but largely scattered because of cliff collapse before the specimen could be collected 

by William Palmer from the top of SZ 9, about 30 cm (1 foot) 

below the base of SZ 10, lower Plum Point Member, Calvert 

Formation; 3.2 km (2.0 miles) south of Chesapeake Beach, 

Calvert County, Maryland (Palmer, 1908). (2) Fragmentary 

scapula with both scapular rods broken off (USNM 8349), possibly collected by G. A. Sieglie from the Plum Point Member of 

the Calvert Formation; Plum Point, Calvert County, Maryland 

(Weems, 1974).

Newly Referred Material. (1) Numerous large 

dorsal and ventral dermal shield fragments (USNM 364381) 

plus two cervical vertebrae, three caudal vertebrae, partial scapula, largely complete right and left pubes, right ilium, and left 

ischium, collected by Robert E. Weems and Stephen R. Horman 

from the Popes Creek Sand Bed, Fairhaven Member, Calvert Formation; in bluffs south of Popes Creek, Charles County, Maryland. (2) Numerous dorsal and ventral dermal shield fragments 

(CMM-V-8773) associated with girdle elements, limb elements, 

and a few skull fragments, collected by Kyle Grimsley and Gary 

Grimsley from the Popes Creek Sand Bed, Fairhaven Member, 

Calvert Formation; in bluffs south of Popes Creek, Charles 

County, Maryland. (3) Patches of dermal shield plates (USNM 

358053), collected by George Fonger and Mr. Miron from SZ 

10, Plum Point Member, Calvert Formation; 4 km (2.5 miles) 

north of Kaufmann Camp, Calvert County, Maryland. (4) Left 

humerus (CMM-V-12), collected by Wally Ashby from SZ 14, 

Plum Point Member, Calvert Formation; Scientists Cliffs, 27 m 

(30 yards) south of groin 1 and 366 m (400 yards) north of Governor Run Road, Calvert County, Maryland. (5) Dermal shield 

ossicles (CMM-V-127), collected by Norman L. Riker from SZ 

17, Drumcliff Member, Choptank Formation; Matoaka Cabins, Calvert County, Maryland. (6) Fragment of dermal shield 

(CMM-V-851) with broad and rounded keels, collected by Jean 

Hooper, David “Dave” J. Bohaska, Paula Bohaska, and Betty 

Cridlin from Little Cove Point Member, St. Marys Formation; 

Chesapeake Ranch Estates north of Driftwood Beach, Calvert 

County, Maryland. (7) Dermal shield ossicle bearing broad and 

rounded ridge (CMM-V-5070), collected by John R. Nance from 

Little Cove Point Member, St. Marys Formation; Chesapeake 

Ranch Estates north of Driftwood Beach, Calvert County, Maryland. (8) Dermal shield ossicle bearing broad and rounded ridge 

(CMM-V-8753), collected by John R. Nance from Little Cove 

Point Member, St. Marys Formation; Chesapeake Ranch Estates 

north of Driftwood Beach, Calvert County, Maryland. (9) Dermal shield ossicles (CMM-V-5133), one with broad and rounded 

keel, collected by John R. Nance and Walt Johns, Windmill 

Point Member, St. Marys Formation; Windmill Point, St. Mary’s 

County, Maryland. (10) Juvenile femur (USNM 433264), collected by S. F. Blake from the Windmill Point Member, St. Marys 

Formation; Windmill Point, St. Mary’s County, Maryland.

Remarks. Isolated dorsal and ventral dermal shield ossicles of this species are occasionally found, but because the combined dorsal and ventral shields of a single Psephophorus turtle 

probably were composed of more than 1,000 ossicles, the dermal 

shields from a single individual could easily become scattered 

across a wide area of Miocene seafloor and create a false sense 

that this species was far more abundant than it actually was. 

On the basis of partial skeletons, only seven or eight individuals 

can be reliably counted. The dermal shields found in the Popes 

Creek Sand Bed generally have low and rounded ridges (Figure 

1.13E), as do the few ridge elements that have been found in 

the St. Marys Formation. In contrast, a number of the ridged 

ossicles found with the holotype dermal shield of Psephophorus 

calvertensis, collected from the upper part of SZ 9 of the Plum 

Point Member, have much higher and more angular ridges (Figure 1.13F), although other ridges from this same specimen are 

lower and more rounded (Figure 1.13G,H). A different specimen 

found in SZ 10 (USNM 358053) does not show indication of 

high or sharply angled ridges.

Wood et al. (1996) thought that the high and sharply angled 

ridge on the dermal shield of the Psephophorus calvertensis holotype was different enough from the lower and more rounded 

ridges on the neotype of P. polygonus to distinguish P. calvertensis from P. polygonus. However, a more recent reevaluation by 

Delfino et al. (2013) of topotype material of P. polygonus from 

the same locality as the neotype has documented that some of 

this associated material also has ridges much higher and sharper 

than the ridges on the neotype. I suspect that the circular patterns 

present on ossicles of the neotype of P. polygonus are probably 

indicative of ventral shield ossicles, which seem to be somewhat 

different from dorsal shield ossicles on the basis of observations 

of specimen USNM 364381. It remains possible that two species 

are represented among this material, but the more likely conclusion is that the higher- and sharper-ridged ossicles found in the 

holotype of P. calvertensis come from the anterior portion of the 

medial ridge on this specimen and that its presence or absence 

likely reflects individual variation, sexual dimorphism, or advanced age of those animals that bore the sharply angled ridges. 

Delfino et al. (2013), on the basis of their recognition of both 

rounded ridges and angular ridges among the topotype material of P. polygonus, suggested the possibility that P. calvertensis

is synonymous with P. polygonus. The similarly mixed occurrences of rounded and sharp ridges among the Miocene material from the Calvert Cliffs and nearby areas strongly supports 

this suggestion. For this reason, the available Miocene material 

from Maryland and Virginia is referred here to Psephophorus

polygonus because (1) it is indistinguishable from the topotype 

material of P. polygonus, (2) it is from the same part of the geologic column (Middle Miocene), and (3) the only living dermochelyid turtle (Dermochelys) is cosmopolitan in its occurrence, 

thus indicating that dermochelyid turtles are and were very wide 

ranging. A femur (USNM 433264) recovered from the Windmill Point Member of the St. Marys Formation has characteristic 

dermochelyid morphology and texture and so almost certainly 

2 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
NUMBER 107 • 2 9

FIGURE 1.13. Dermal shield fragments of Psephophorus polygonus. (A) Ventral shield fragment (USNM 364381) in ventral (external) view; natural shield border at top. (B) Dorsal shield fragment (USNM 364381) in dorsal (external) view; natural shield border 

at left side of top. (C, D) Dorsal shield fragments of “P. calvertensis” holotype (USNM 6059) in dorsal (external) view. (E) Rounded 

and low dorsal shield ridge region (USNM 364381) in cross-sectional view. (F) Angular and high dorsal shield ridge region of “P. calvertensis” holotype (USNM 6059) in cross-sectional view. (G, H) Rounded and low ridge-bearing shield ossicles of “P. calvertensis” 

holotype (USNM 6059) in dorsal and cross-sectional views. (I, J) Rounded and low ridge-bearing platelet (USNM 442461) in dorsal 

and cross-sectional views.
pertains to P. polygonus (Figure 1.14K–N). It is only about 5 

cm in length, so unlike all other P. polygonus material found so 

far, it belonged to a juvenile animal. In Dermochelys, the femur 

is about one-sixth the length of the dermal shield; this implies 

that the juvenile P. polygonus femur from the Late Miocene St. 

Marys Formation came from an animal that had a dermal shield 

and body length only about 30 cm (1 foot) long. The absence of 

any obviously subadult material from the Calvert and Choptank 

Formations suggests that P. polygonus did not nest or grow up in 

this region during the Early and Middle Miocene.

The posterior portion of a parietal bone was found with 

specimen CMM-V-8773 (Figure 1.15I). It is thick and has a typical Psephophorus conformation. Notable is the presence of a 

large depression on the dorsal surface of this bone that partially 

healed before the animal died. It seems likely that this wound was 

caused by a tooth of either the large crocodilian Thecachampsa 

antiquus or the large squalodontid Squalodon whitmorei, both 

of which occur in this same bed at this outcrop.

With the possible exception of one or two dermal shield ossicles, apparently found in the Pliocene or Pleistocene strata of 

the Lee Creek Mine in North Carolina, no remains of the dermochelyid taxon Dermochelys coriacea have ever been found in the 

Neogene or Pleistocene fossil record. The oldest certainly identified remains of Dermochelys are of Middle to Late Holocene 

age. The anatomical differences in these two taxa indicate that 

they have had a long separate evolutionary history, but the Neogene fossil record is highly biased for unknown reasons in favor 

of Psephophorus and against Dermochelys (Frazier et al., 2018).

Family Emydidae Rafinesque, 1815

Subfamily Deirochelyinae Agassiz, 1857

Genus Deirochelys Agassiz, 1857

Turtle – Deirochelys carri – Emydidae

Deirochelys reticulata (illustration by Brenna Litynski)

Shell of Deirochelys reticulata (USNM 220867)

Type Species. Deirochelys reticulata (Latreille, 1801).

“Deirochelys” carri Jackson, 1978

Deirochelys carri Jackson, 1978:43, fig. 11.

Deirochelys carri Auffenberg, 2001:127–128.

“Deirochelys” carri Vlachos, 2018:17.

Referred Material. Proximal portion of third 

left costal (CMM-V-8755), found by Donald J. Morgan III 

in the Windmill Point Member of the St. Marys Formation; 

Windmill Point, St. Mary’s County, Maryland.

Description. Costal has narrow, low, parallelaligned ridges running anteroposteriorly on its external surface with sulcal grooves marking the borders of dermal scutes, 

a rough-textured surface on both its dorsal and ventral sides, 

and a rudimentary, dorsoventrally compressed, bladelike rib 

head.

Remarks. This specimen (Figure 1.16 A,B) is the 

first record of a chicken turtle from the Miocene of the midAtlantic region. “Deirochelys” carri is known from the Late 

Miocene of Florida (Hulbert, 2001), so the present specimen 

does not constitute a temporal extension for this genus, although it is a considerable geographic range extension of its 

Miocene distribution. This specimen is assigned to “Deirochelys” carri because it is indistinguishable from that species, 

it comes from the same stratigraphic interval (Late Miocene), 

and there is no evidence for any geographic or ecological barriers between the Florida and mid-Atlantic regions during the 

Miocene. Vlachos (2018) agreed that Deirochelys carri Jackson, 1978 is a deirochelyine turtle, but he was skeptical that 

it should be assigned to the living genus Deirochelys and so 

placed its generic name in quotation marks. That designation 

is followed here.

3 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
FIGURE 1.14. Vertebrae and femur of Psephophorus polygonus. (A, B) Seventh cervical vertebra (USNM 

364381) in left lateral and ventral views. (C) Eighth cervical vertebral arch (USNM 364381) in left lateral view. 

(D, E) Eighth cervical vertebral centrum (USNM 364381) in ventral and posterior views. (F, G) Anterior caudal 

vertebra (USNM 364381) in left lateral and posterior views. (H, I) Posterior caudal vertebra (USNM 364381) in 

left lateral and anterior views. (J) Posterior caudal vertebra (USNM 364381) in posterior view. (K–N) Juvenile 

femur (USNM 433264) in proximal, distal, dorsal, and lateral views.

NUMBER 107 • 31
3 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 1.15. Girdle elements and humerus of Psephophorus polygonus. (A, B) Scapula (USNM 364381) in lateral and articular views. (C, D) Right and left pubes (USNM 364381) in ventral view. (E) Right ischium (USNM 364381) in ventral view. (F) 

Right ilium (USNM 364381) in ventral view. (G) Coracoid (CMM-V-8773) in external view. (H) Left humerus (CMM-V-12) in 

dorsal view. (I) Posterior portion of left parietal (CMM-V-8773) in dorsal view, anterior end up. Note partially healed puncture 

wound at top left.
FIGURE 1.16. (A, B) Proximal costal fragment of “Deirochelys” carri (CMM-V-8755) 

in external and internal views. (C, D) Posterior peripheral of Trachemys inflata? (CMMV-4663) in external and posterior views. (E) Distal end of sixth left costal of Trachemys 

inflata (CMM-V-8950). (F, G) Right hyoplastron of Pseudemys caelata (HSMC 2017-1) 

in ventral and internal views; “en” marks the location of the lower right corner of the entoplastron. (H) Nuchal of Pseudemys williamsi (CMM-V-4327) in dorsal view. (I) Fourth 

through seventh right peripherals of Pseudemys williamsi (USNM 639758) in lateral view. 

(J) Neural of Pseudemys williamsi (USNM 639758) in dorsal view. (K–M) Left epiplastron of Trachemys inflata (CMM-V-4663) in dorsal (internal), ventral (external), and anterior views. (N–P) Neural element of Graptemys sp. (CMM-V-1895) in dorsal (external), 

anterior, and ventral (internal) views.

NUMBER 107 • NUMBER 107 • 3 3
3 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Genus Graptemys Agassiz, 1857

Turtle – Graptemys – Emydidae

Graptemys geographica (illustration by Brenna Litynski)

Shell of Graptemys geographica (USNM 220876)

Type Species. Graptemys geographica (Lesueur, 1817).

Graptemys sp.

Graptemys barbouri Jackson, 1975:213–219.

Graptemys kerneri Ehret and Bourque, 2011:575–587.

Referred Material. Neural element (CMM-V1895), collected by William Holliman from the upper Yorktown 

Formation at Rice’s Fossil Pit, Hampton, Virginia.

Diagnosis. Small turtle with thick hexagonal neurals, 

lateral margins planar but anterior margin strongly concave and 

posterior margin strongly convex. Anterior neurals have a pronounced dorsal keel.

Remarks. Graptemys geographica is the only species 

of Graptemys that occurs today in the Maryland and Virginia 

regions. It mostly occurs in southwestern Virginia within the Tennessee Valley drainage region, but a few local populations are 

found in eastern Virginia in Prince William County and the city 

of Hampton (Virginia Herpetological Society website). In Maryland, populations are known only from along the Susquehanna 

River in Cecil and Harford Counties (Maryland Department of 

Natural Resources, 2023). The presence of a neural referable to 

Graptemys in the Late Pliocene Yorktown Formation of southeastern Virginia (Figure 1.16N–P) is somewhat surprising because 

this specimen is far older than any other fossil material of Graptemys reported from anywhere in the eastern United States (Ehret 

and Bourque, 2011). Evidence of Graptemys has been reported as 

far back as the Oligocene in South Dakota (Clark et al., 1967), so 

it seems likely that this turtle originated in the Mississippi Valley 

drainage system and did not successfully invade the northern Atlantic Coastal Plain drainages until Late Pliocene time. Although 

this specimen can be firmly referred to Graptemys, it is far from 

sufficient to provide a species-level identification.

Genus Chrysemys Gray, 1844

Turtle – Chrysemys – Emydidae

Chrysemys isoni (illustration by Brenna Litynski)

Shell of Chrysemys isoni
NUMBER 107 • 3 5

Type Species. Chrysemys picta (Schneider, 1783).

Chrysemys isoni Weems and George, 2013

Chrysemys isoni Weems and George, 2013:576–578.

Chrysemys isoni Vlachos, 2018:47.

Holotype. One largely complete nuchal element 

(CMM-V-4664).

Holotype Locality and Horizon. Side gulley 

of Pamunkey River where it forms the boundary between King 

William and New Kent Counties, Virginia. Probably derived 

from the Fairhaven Member of the Calvert Formation in strata 

equivalent in age to the Popes Creek Sand Member of Gibson 

(1983; =the lower “Newport News unit” of Powars and Bruce, 

1999).

Newly Referred Material. (1) Partial carapace 

and largely complete plastron of a single individual (CMM-V8881), collected by Billy Palmer from the Plum Point Member (SZ 12), Calvert Formation; south of Plum Point, Calvert 

County, Maryland. (2) Right epiplastron (CMM-V-2491), found 

by Jean Hooper from the Little Cove Point Member of the St. 

Marys Formation; Driftwood Beach, Calvert County, Maryland.

Diagnosis. Anterior region of nuchal greatly 

thickened, with an anterior border strongly constricted and 

deeply crenulated; lateral borders with adjacent first peripherals distinctly concave; cervical scute large and elongate on 

both dorsal and ventral sides, ventral side much longer than 

dorsal side. Entoplastron diamond shaped with rounded 

anterior and posterior edges; epiplastra lack the prominent 

knob found in C. picta near the middle of their dorsal (internal) surfaces.

Remarks. The Palmer specimen, together with the type 

nuchal, provides sufficient information to reconstruct the entire 

carapace and plastron (Figure 1.17G,H). These specimens together make Chrysemys isoni the best known nonmarine turtle 

from the Delaware-Maryland-Virginia Miocene. The right epiplastron is stratigraphically somewhat younger than the Palmer 

specimen but is indistinguishable from it and lacks the prominent 

dorsal knob present in living Chrysemys picta. Therefore, the St. 

Marys epiplastron is referred to Chrysemys isoni despite the age 

difference between the Calvert and St. Marys Formations. Vlachos 

(2018) designated this taxon as a nomen dubium because he considered a single nuchal element to be insufficient to define a new 

species among pan-emydid turtles. Because the Palmer specimen 

has greatly expanded our knowledge of the anatomy of this species, this objection is no longer true.

Genus Trachemys Agassiz, 1857

Turtle – Trachemys scripta – Emydidae

Trachemys inflata (illustration by Brenna Litynski)

Shell of Trachemys scripta (from Boulenger, 1889)

Type Species.Trachemys scripta (Thunberg in Schoepff, 1792).

Trachemys inflata

Chrysemys inflata Weaver and Robertson, 1967:56–58.

Trachemys inflata Auffenberg, 2001:128–132.

Trachemys sp. Zug, 2001:214.

Trachemys inflata Parmalee et al., 2002:233–238.

Trachemys inflata Holman and Parmley, 2005:311–314.

Trachemys sp. Weems and George, 2013:578.

Chrysemys inflata Vlachos, 2018:47.
FIGURE 1.17. (A) Portions of the anterior carapace of Chrysemys isoni (CMM-V-8881) in external view. (B) Nuchal of Chrysemys isoni (CMM-V-4664) in dorsal (external) view. (C) First suprapygal of Chrysemys isoni (CMM-V-8881) in dorsal view. (D) 

Pygal and last right peripheral of Chrysemys isoni (CMM-V-8881) in dorsal view. (E) Posterior plastron fragment of Chrysemys 

isoni (CMM-V-8881) in ventral (external) view. (F) Anterior plastron of Chrysemys isoni (CMM-V-8881) in external view. (G) 

Restoration of carapace of Chrysemys isoni. (H) Restoration of plastron of Chrysemys isoni.

3 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
NUMBER 107 • 3 7

Previously Referred Material. (1) Posterior 

peripheral (USNM 358314), collected by Peter J. Harmatuk, 

from the Lee Creek Mine, Aurora, North Carolina; either from 

the Pungo River Formation or the Sunken Meadow Member of 

the Yorktown Formation. (2) Pygal (USNM 186774), collector 

unknown, from the Lee Creek Mine, Aurora, North Carolina; 

either from the Pungo River Formation or the Sunken Meadow 

Member of the Yorktown Formation. (3) Posterior peripheral 

(CMM-V-4663), found by Ron Ison in a ravine along the Pamunkey River where it forms the boundary between New Kent 

and King William Counties, Virginia; either from the Popes 

Creek Sand Bed of the Fairhaven Member of the Calvert Formation or the Eastover Formation (Weems and George, 2013). 

Newly Referred Material. (1) Distal end of 

sixth left costal (CMM-V-8950), collected by Betty Cridlin from 

the Little Cove Point Member, St. Marys Formation; Chesapeake 

Ranch Estates, Calvert County, Maryland. (2) Left epiplastron 

(CMM-V-4328), collected by Rose and David Schooff, from 

New Kent County, Virginia; probably (but not certainly) found 

in the Eastover Formation.

Description. Posterior peripheral elements with a 

strongly bifurcated external margin, posterior lobe much more 

elongated than anterior lobe, sulcal grooves clearly visible. 

Costals have a strongly crenulated external surface. Epiplastron about as long as wide with an epiplastral lip that projects 

strongly forward and has an angular anterolateral corner.

Remarks. The bifurcated external margin of the posterior peripheral (Figure 1.16C,D) is diagnostic for Trachemys

among Neogene, Pleistocene, and Holocene southeastern U.S. 

turtles, and its exceptionally deep bifurcation is most typical of 

T. inflata. The strong forward projection of the epiplastral lip 

of the epiplastron (Figure 1.16K–M), with its sharp anterolateral external border and inward slope toward the midline, also 

is characteristic of T. inflata and unlike the living species T. 

scripta. The size of the epiplastron illustrated here is smaller and 

somewhat less anteroposteriorly elongate than the specimen illustrated in Auffenberg (2001), but the reason is likely due to the 

specimen illustrated here being immature. The epiplastral lips on 

the illustrated specimens from Tennessee (Parmalee et al., 2002) 

and Nebraska (Holman and Parmley, 2005) are strongly serrated along their anterior margins, but the specimen illustrated 

in Auffenberg (2001) and the specimen illustrated here are not. 

Vlachos (2018) observed that this species was based originally 

only on a nuchal plate that was differentiated from other emydid 

species by the presence of a deep nuchal notch associated with 

a significant cervical scute protrusion. He concluded that these 

characteristics are common among emydids, they are not diagnostic for any particular species, and therefore this species is 

a nomen dubium. I, however, can find no other turtle material 

reported from the Miocene or Pliocene of the Atlantic Coastal 

Plain that can be confused with this taxon, and the morphology of the posterior peripheral and costal elements reported here 

(Figure 1.16C–E) and in Auffenberg (2001) clearly indicates that 

this material pertains to a species of Trachemys and not Chrysemys. Therefore, the name Trachemys inflata is retained here 

until such time as clear evidence is found for the existence of a 

second species in the Miocene of the Atlantic Coastal Plain that 

has carapace elements that could be confused with the specimens 

described here. In Florida, T. inflata ranges from the Late Miocene to the Early Pliocene. It is not altogether certain whether the 

two posterior peripherals inferred to be from the Calvert Formation are correctly assigned to that unit; the specimen from the 

Pamunkey River (Weems and George, 2013) possibly could be 

from the Eastover Formation, and the specimen from the Lee 

Creek Mine (Zug, 2001) may well be from the Sunken Meadow 

Member of the Yorktown Formation and not from the Pungo 

River Formation. Therefore, this species is here questionably reported as being present in the Early Miocene (Burdigalian) part 

of the Calvert Formation and firmly reported from the Late Miocene St. Marys Formation.

Genus Pseudemys Gray, 1856

Turtle – Pseudemys – Emydidae

Pseudemys williamsi (illustration by Brenna Litynski)
3 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Shell of Pseudemys williamsi (UF 11561)

Type Species. Pseudemys concinna (Le Conte, 1830).

Pseudemys williamsi (Rose and Weaver, 1966)

Chrysemys williamsi Rose and Weaver, 1966:41–44, fig. 1 (original description).

Pseudemys williamsi Auffenberg, 2001:128–129.

Pseudemys williamsi Vlachos, 2018:18.

Referred Material. (1) Anterior nuchal (CMMV-4327), collected by Rose and David Schooff, probably 

found in the Eastover Formation; New Kent County, Virginia. 

(2) Partial carapace (USNM 639758) including a neural, left 

peripherals 4 through 7, and right peripheral 7, found by 

Robert E. Weems in the Eastover Formation; north bank of 

Richmond City Landfill at end of P Street, Richmond, Virginia (stratigraphy of locality described in Johnson and Ward, 

1990:42).

Description. Nuchal with characteristic P. williamsi

conformation. Costals and peripherals have a nearly smooth, 

dense external surface with prominent sulcal grooves that mark 

the borders of dermal scutes. 

Remarks. These specimens (Figure 1.16H–J) are 

the first convincing records of Pseudemys williamsi from 

the Maryland-Virginia Miocene, although one specimen 

(Figure 1.16C) identified as Trachemys from the Calvert 

Formation in Virginia by Weems and George (2013) may 

also pertain to this species. The nuchal scute shape is clearly 

that of P. williamsi, and the lack of any surface sculpture 

pattern and the relative proportions of the peripherals of 

the specimen from Richmond also are characteristic of 

Pseudemys and different from those of other deirochelyine 

turtles. The locality data for the nuchal is vague, but on 

the basis of the known occurrence of late Cenozoic units 

in New Kent County, this specimen must have come from 

the Calvert, Eastover, or Yorktown Formation. The preservation seems typical of Eastover vertebrate fossils, and P. 

williamsi is known only from Late Miocene beds in Florida 

(Hulbert, 2001), so derivation from the Eastover Formation seems likely. This species likely will be found eventually in the St. Marys Formation.

Pseudemys caelata Hay, 1908

Pseudemys caelata Hay, 1908:356–357 (original description).

Chrysemys carri Rose and Weaver, 1966:44–47.

Pseudemys caelata Jackson, 1976:655–659.

Pseudemys caelata Auffenberg, 2001:129.

Pseudemys caelata Vlachos, 2018:60.

Newly Referred Material. Right hyoplastron 

(HSMC 2017-1), found by Donna Richardson from the Windmill Point Member of the St. Marys Formation; Chancellors 

Point, St. Mary’s County, Maryland. 

Description. Hyoplastron has a dense external surface 

with closely spaced, low ridges that roughly parallel bone borders; 

prominent sulcal grooves mark the borders of dermal scutes. Anterior pectoral scute lies far forward on the hyoplastron, crossing 

the posterior edge of the entoplastron. Peripheral has an irregular rough surface texture and broad ridges and troughs trending 

transversely across its proximal region. 

Remarks. The dense surface texture and the sculpture pattern on material illustrated here (Figure 1.16F,G) is 

characteristic of P. caelata, which is known from beds of 

similar age in Florida (Auffenberg, 2001). Vlachos (2018) 

followed Hay (1908) in ascribing a Pleistocene age to this 

taxon, but Rose and Weaver (1966:44) and Auffenberg 

(2001:129) both placed a firm source for this taxon at the 

McGehee Farm site and ascribed a Late Miocene age to this 

material. Vlachos (2018) felt that the holotype nuchal described by Hay (1908) was insufficient to erect a new species 

of Pleistocene Pseudemys, but the Late Miocene age of this 

material and the fact that the material of its junior synonym 

Chrysemys carri includes a nearly complete carapace and 

plastron together provide ample evidence that this is a valid 

taxon. The only other Late Miocene Pseudemys from the 

Atlantic Coastal Plain (Pseudemys williamsi) has a smooth 

carapace, unlike the sculptured carapace of Pseudemys caelata, so there is no ambiguity regarding to which of these 

Late Miocene species this material belongs.
NUMBER 107 • 3 9

Family Testudinidae Batsch, 1788

Subfamily Xerobatinae Agassiz, 1857

Genus Hesperotestudo Williams, 1950

Turtle – Hesperotestudo crassiscutata – Testudinidae

Hesperotestudo crassiscutata (illustration by Brenna Litynski)

Shell of Hesperotestudo crassiscutata (after Auffenberg, 1963)

Type Species. Hesperotestudo percrassa (Cope, 1899).

Hesperotestudo ducateli (Collins and Lynn, 1936)

Testudo ducateli Collins and Lynn, 1936:166–171 (original description).

Testudo ducateli Kuhn, 1964:116.

Geochelone (Caudochelys) ducatelli Auffenberg, 1974:147.

Hesperotestudo (Caudochelys) ducateli Weems and George, 2013:579.

Hesperotestudo ducateli Vlachos, 2018:39.

Holotype. USNM 13783, complete plastron and a 

fragmentary carapace including the second neural, second and 

third right costals, fourth to eighth right peripherals, and fourth 

left peripheral.

Holotype Locality and Horizon. Specimen 

excavated by R. Lee Collins and W. Gardner Lynn from a cut 

bank on the west side of the Chesapeake Beach–Plum Point road, 

5.5 km (3.4 miles) south of the old Chesapeake Beach Railroad 

Station, located about 0.4 km (0.25 mile) inland from the Calvert Cliffs, Calvert County, Maryland; SZ 10, Plum Point Member, Calvert Formation.

Previously Referred Material. Fourth left peripheral (CMM-V-4665), collected by Gary Grimsley from the 

basal lag bed of SZ 11, Plum Point Member, Calvert Formation; 

Plum Point, Calvert County, Maryland (Weems and George, 2013).

Newly Referred Material. Neural element 

(CMM-V-8882), collected by Victor Perez from the beach at 

Randle Cliffs where SZs 4–12 are exposed, Plum Point Member, 

Calvert Formation; Randle Cliffs, Calvert County, Maryland.

Diagnosis. Relatively small tortoise, with an estimated 

carapace length of about 25 cm. The only preserved neural is the 

second; it is wider than long, about 4 mm thick, and octagonal in 

outline. Anterior costals elongate, about 7 mm thick, and bear distinct sulcal grooves; peripherals also elongate in characteristic testudinid fashion; sulcal grooves on the carapace well developed except 

for the groove that separates the costal and marginal scutes that follows the costoperipheral suture quite closely. Carapace rather high 

and tumid. Plastron typically 15 to 20 mm thick but ranges up to 40 

mm near the inguinal buttresses and down to 4 mm near the hyoplastral-hypoplastral suture. There is a well-developed anal notch, a 

slightly projecting epiplastral lip, and a firm and extended articulation with the carapace. The anterior end of the plastron is strongly 

curved upward, and the dorsal surface of the epiplastral lip is almost 

horizontal. The ventral surface of the plastron is markedly concave 

just in front of the inguinal notches, and the corresponding visceral 

surface is elevated, suggesting the type individual was a male. The 

inguinal buttresses are strongly developed, but rather slender at the 

point of attachment with the peripherals and extend almost at right 

angles to the plastral axis. The right buttress runs from the lower 

posterior part of peripheral 7 somewhat obliquely across peripheral 

8, which is very much thickened in the region of attachment and appears to have ended before reaching the upper margin of this plate. 

The axillary buttresses are well developed and slightly oblique to the 

plastral axis. They probably did not reach beyond the upper margin 

of the fourth peripheral. The entoplastron is roughly octagonal in 

outline on its outer surface, with a tapering anterior margin bearing a small angle behind the gulo-humeral sulcus and another at 

the epihyoplastral suture. Plastral sulci are all well-defined. Plastral 

scutes slightly encroach on the peripheral bones, and there is a much 

smaller overlap of the marginal scutes onto the plastral elements. 

The pectoral scute of the plastron overlapped onto peripheral 4; the 

abdominal scute overlapped onto peripherals 5 through 7, and the 

inguinal scute overlapped onto peripherals 7 and 8. The inguinal 

scute was relatively large and roughly rectangular in outline.
4 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Remarks. Hesperotestudo ducateli remains a very rare 

turtle in the Calvert Cliffs (Figure 1.18A–D), being definitely 

known only from SZ 10 and basal SZ 11. It has not been reported from anywhere other than the Calvert Cliffs.

Hesperotestudo williamsi Auffenberg, 1964

Geochelone williamsi Auffenberg, 1964:1–11.

Geochelone (Caudochelys) williamsi Auffenberg, 1974:147.

Geochelone sp. indet. Holman, 1998:142.

Hesperotestudo (Caudoceheys) wilsoni Weems and George, 2013:580.

Hesperotestudo (Caudoceheys) williamsi Weems and George, 2014:204.

Hesperotestudo williamsi Vlachos, 2018:43.

Previously Referred Material. (1) Two neurals (USNM 540747 and USNM 483391), collected by G. Simonson and Ralph E. Eshelman from the Cheswold sands, 

Fairhaven Member, Calvert Formation; Pollack Farm site, Kent 

County, Delaware. (2) Two partial costal elements (USNM 

483391 and USNM 540751), collected by G. Simonson from 

the Cheswold sands, Fairhaven Member, Calvert Formation; 

Pollack Farm site, Kent County, Delaware. (3) Posterior portion of left hypoplastron (USNM 483391), collected from the 

Cheswold sands, Fairhaven Member, Calvert Formation; Pollack 

Farm site, Kent County, Delaware. (4) Right humerus (CMMV-4667), collected by Reed George from the Popes Creek Sand 

Bed, Fairhaven Member, Calvert Formation; right (south) bank 

of Pamunkey River, New Kent County, Virginia (Weems and 

George, 2013, 2014).

Newly Referred Material. Partial entoplastron 

(CMM-V-8952), collected by Kyle Grimsley from the Popes 

Creek Sand Bed, Fairhaven, Member, Calvert Formation; south 

of Popes Creek, Charles County, Maryland.

Description. Large tortoise with an estimated length 

of about 34 cm, distinctly larger than H. ducateli. Neurals wider 

than long, dorsal surface faintly rugose. Costals narrow, long, 

and preserved segments nearly straight; costals thicker than in H. 

ducateli. Entoplastron diamond shaped, more narrow than long. 

Humerus large with a robust, stout, and only slightly sigmoidal 

shaft.

Remarks. Vlachos (2018) cited the paper by Weems 

and George (2013), but he apparently was unaware of the addendum to this paper published soon afterward (Weems and 

George, 2014) that changed their incorrect use of the name 

Hesperotestudo wilsoni for this material to the correct name, 

Hesperotestudo williamsi. As a result, Vlachos (2018) was in 

error when, in his analysis of Hesperotestudo williamsi, he 

indicated that to date, no specimens have been referred to this 

taxon. For the same reason, he was incorrect in stating that 

his use of the combination Hesperotestudo williamsi was new 

because this was the combination used in Weems and George 

(2014). Hesperotestudo williamsi was a distinctly larger tortoise than Hesperotestudo ducateli and had a relatively thicker 

carapace (compare Figure 1.18C with Figure 1.18E). So far, 

it is known only from the Burdigalian Fairhaven Member of 

the Calvert Formation at Pollack Farm, Delaware; from Popes 

Creek, Maryland; and from the Pamunkey River in New Kent 

County, Virginia. Although slightly damaged anteriorly, the 

conformation of the recently discovered entoplastron found 

at Popes Creek, Maryland (Figure 1.18J,K), is readily discernable, being diamond shaped as in H. williamsi and not octagonal as in H. ducateli (Figure 1.18A). The Popes Creek 

entoplastron here assigned to H. williamsi is nearly the same 

size as the holotype entoplastron of H. williamsi, but it is distinctly narrower than the holotype element, which is nearly 

as wide as long (Auffenberg, 1964: fig. 2). The proportions 

of the entoplastron of H. williamsi are based only on the holotype specimen, so it is impossible to judge for now whether 

the difference in relative width between the holotype entoplastron and the entoplastron from Popes Creek, Maryland, 

represents sexual dimorphism, individual variation within 

a single species, or a species-level distinction between these 

two specimens. Although it is possible that more and better 

Calvert material here assigned to Hesperotestudo williamsi

might demonstrate a species-level distinction between it and 

the holotype material from Texas, until such time as this can 

be demonstrated, the Calvert material remains assigned to 

H. williamsi.

Genus Floridemys Auffenberg, 1963

Turtle – Floridemys nana – Testudinidae

Floridemys nana (illustration by Brenna Litynski)
NUMBER 107 • 4 1

FIGURE 1.18. (A) Plastron of Hesperotestudo ducateli (USNM 13783) in ventral (external) view. (B) Second neural and second and 

third right costals of Hesperotestudo ducateli (USNM 13783) in dorsal (external) view. (C) Sixth right peripheral of Hesperotestudo 

ducateli (USNM 13783) in posterior view. (D) Fourth through sixth right peripherals of Hesperotestudo ducateli (USNM 13783) 

in right lateral view. (E, F) Costal fragment of Hesperotestudo williamsi (USNM 483391) in lateral and dorsal (external) views. (G) 

Odd-numbered neural element of Hesperotestudo williamsi with sulcal groove (USNM 483391) in dorsal (external) view. (H) Oddnumbered neural element of Hesperotestudo williamsi with sulcal groove (USNM 540747) in dorsal (external) view. (I) Left humerus of 

Hesperotestudo williamsi (CMM-V-4667) in anterior view. (J, K) Entoplastron of Hesperotestudo williamsi (CMM-V-8952) in ventral 

and lateral views.
4 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Shell of Floridemys nana (after Auffenberg, 1963)

Type Species. Floridemys nana (Hay, 1916).

Floridemys hurdi Weems and George, 2013

Floridemys hurdi Weems and George, 2013:580 (original description).

Floridemys hurdi Vlachos, 2018:55.

Holotype. A well-preserved nuchal (CMM-V-4666).

Holotype Locality and Horizon. Float material found on the beach beneath Randle Cliff, Calvert County, 

Maryland. The cliff includes strata belonging to SZs 4–12 of the 

Plum Point Member of the Calvert Formation. All other land 

turtle remains from this interval of the Calvert Formation have 

come from SZs 10, 11, and 12, so these are the most likely layers 

from which this specimen came.

Referred Material. Nuchal (CMM-V-9976), 

collected by Mike Ellwood as beach float from a cliff that contains beds ranging from SZ 12 (Plum Point Member, Calvert 

Formation) to SZ 19 (Boston Cliffs Member, Choptank Formation), Warriors’ Rest along the Calvert Cliffs, Calvert County, 

Maryland.

Diagnosis. On the dorsal surface, the cervical scute of 

Floridemys hurdi is about twice as long as wide, whereas the 

cervical scute of Floridemys nana is about as long as wide. Anterior border of the first pleural scutes reach onto the posterior 

borders of the nuchal of F. nana but are posterior to the nuchal in F. hurdi. The nuchal of F. hurdi pertains to a turtle about 

30% larger than F. nana, but both species are much smaller than 

Hesperotestudo or Gopherus. Anterior nuchal border of all species of Floridemys are much narrower than in Hesperotestudo

or Gopherus.

Remarks. Since the description of the holotype nuchal of Floridemys hurdi, only one additional nuchal element 

has been found for this species of pygmy tortoise. The dorsal surface of the nuchal of F. hurdi somewhat resembles the 

nuchal element of emydid turtles in its constricted anterior 

border and narrow but elongated cervical scute. However, the 

great lateral expansion of the cervical scute on the ventral 

side of the nuchal belies emydid assignment and is compatible 

only with assignment to the family Testudinidae. Similarly, 

the arrangement of the costals in the closely related species 

F. nana, alternately wide and narrow at their distal ends, is a 

characteristic found in testudinid but not emydid turtles. The 

nuchal in all of the described species of Floridemys is about as 

wide as long and also narrow along the anterior border. This 

conformation is quite different from the nuchals of Hesperotestudo and Gopherus, which are both much wider than long 

and have long anterior borders (see Weems and George, 2013: 

fig. 12). The type specimen of Floridemys was described by 

Hay (1916) as Bystra nanus. That generic name was preoccupied, so the replacement name Floridemys was proposed 

by Williams (1950). Because Floridemys was a dwarf tortoise 

known only from shallow marine sediments near the Miocene 

Atlantic coastline, Weems and George (2013) suggested that 

it was normally an inhabitant of the Miocene Atlantic barrier 

islands. A propensity to burrow long tunnels into sand, as 

done by the living Gopherus polyphemus, would have been a 

very helpful survival strategy in the unstable environment of 

barrier islands.

Vlachos (2018) considered Floridemys hurdi to be a 

nomen dubium on the grounds that a single nuchal element 

was insufficient to diagnose a new species and because of “the 

unknown provenance of the specimen.” Although the specimen was a beach find, the adjacent cliff includes only SZs 

4–12, which specifically represent the lower half of the Plum 

Point Member of the Calvert Formation. This stratigraphic 

interval and specific locality hardly constitute an “unknown 

provenance.” Similarly, the strikingly different conformation 

of the nuchal scute in Floridemys hurdi in comparison to the 

nuchal scute of Floridemys nana provides a clear difference 

between these two taxa that is reinforced by the newly discovered specimen of F. hurdi, which has a nuchal scute very 

similar in conformation and size to that of the type specimen 

of F. hurdi (Figure 1.19) and unlike that in F. nana. Therefore, 

Floridemys hurdi remains a valid taxon. Auffenberg (1964) 

suggested that Floridemys nana might be a late descendant of 

the Stylemys lineage, but Vlachos (2018) pointed out that the 

shell morphology in the Stylemys lineage is strikingly different 

from the shell morphology found in Floridemys, which instead 

has a morphology much closer to that of the clade of derived 

tortoises (Testudininae). Except for Floridemys, the Testudininae are unknown in North America. Interestingly, this suggests that Floridemys may have reached North America by a 

sweepstakes current dispersal across the Atlantic Ocean from 

Africa (Vlachos, 2018). A reverse pattern of current dispersal 

has been convincingly demonstrated for the Pleistocene tortoise Hesperotestudo bermudae, which was rafted eastward 

from southeastern North America to Bermuda (Meylan and 

Sterrer, 2000).
FIGURE 1.19. (A, B) Nuchal of Floridemys hurdi (CMM-V-9976) in dorsal (external) and ventral (internal) 

views. (C, D) Nuchal of Floridemys hurdi (CMM-V-4666) in dorsal (external) and ventral (internal) views. 

(E, F) Nuchal of Floridemys nancei sp. nov., (CMM-V-3726) in dorsal (external) and ventral (internal) views. 

(G–I) Comparison of the nuchals of Floridemys nana, Floridemys hurdi, and Floridemys nancei in anterodorsal 

(external) views.

NUMBER 107 • 4 3
4 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Floridemys nancei sp. nov.

Holotype. A nearly complete nuchal (CMM-V-3726) 

named for its discoverer, John R. Nance.

Holotype Locality and Horizon. Float material found on the beach at Chesapeake Ranch Estates, Calvert County, Maryland; the only unit at this locality producing 

vertebrate remains is the Little Cove Point Member, St. Marys 

Formation.

Etymology. Nancei was created in accordance with 

Article 31.1.2 of the ICZN by adding an “i” to “Nance.”

Diagnosis. On the dorsal surface, the cervical scute of 

Floridemys nancei is about four times as long as wide, whereas 

the cervical scute of Floridemys hurdi is about twice as long as 

wide and the cervical scute of Floridemys nana is about as long 

as wide (Figure 1.19). Anterior border of the first pleural scutes 

reach onto the posterior borders of the nuchal as in F. nana but 

unlike in F. hurdi, where the anterior borders of the pleural scutes 

are posterior to the nuchal. The nuchal of F. nancei pertains to a 

turtle larger than either F. hurdi or F. nana, but all three species 

are much smaller than all species of Hesperotestudo and Gopherus. Anterior nuchal borders of all three Floridemys species 

are also much narrower than in Hesperotestudo or Gopherus.

Remarks. The holotype specimen of Floridemys nancei

came from the lower Late Miocene (Tortonian) Little Cove Point 

Member of the St. Marys Formation, and the holotype specimen of 

Floridemys hurdi came from the basal Middle Miocene (Serravallian) portion of the Plum Point Member of the Calvert Formation. 

Hay originally believed that the holotype specimen of Floridemys 

nana came from Pliocene strata, but more recent opinion is that it 

came from Early Miocene or possibly even late Oligocene strata 

(Auffenberg, 1974; Hulbert, 2001:132). The nuchals of these three 

species can be arranged as an evolutionary progression (Figure 

1.19E–G) in which the cervical scute becomes progressively longer on the dorsal surface of the nuchal and the overall body size 

becomes progressively larger over time. This progression, however, 

can be true only if the holotype specimen of Floridemys nana came 

from Early Miocene or older strata of Florida. An attempt was 

made to definitively establish the age of the holotype specimen of 

F. nana by processing a small sample of matrix attached to the 

holotype for calcareous nannofossils, but none were found. What 

was observed, however, is that the matrix in which the holotype 

was buried consists mostly of micritic dolomite (Jean Self-Trail, 

U.S. Geological Survey, oral communication, 2017). According 

to Tom Scott (Florida Geological Survey, emeritus, written communication, 2018), the Aquitanian-Serravallian Hawthorn Group 

in northern Florida consists of interbedded siliciclastic rocks and 

dolomitic carbonates. The latter lithology matches the lithology in 

which the holotype of Floridemys nana was entombed, so F. nana

likely was buried originally in a dolomitic bed within a formation 

of the Hawthorn Group. The discovery of the holotype of F. nana

in a hard-rock phosphate deposit assigned to the “Alachua Formation” indicates that it was transported from its original Hawthorn 

Group stratum and redeposited in a sinkhole deposit that likely 

accumulated during the Late Miocene (Tortonian). Miners often 

found fossils associated with hard-rock phosphate deposits, and 

many of them were derived from older deposits. On the basis of 

the time range of the Hawthorn Group in northern Florida, the 

original Hawthorn Group stratigraphic horizon of the type specimen of Floridemys nana almost certainly lies somewhere within the 

Aquitanian, Burdigalian, or Serravallian stage. If the holotype of 

F. nana came from the Early Miocene (Aquitanian or Burdigalian) 

part of the Hawthorn Group, then an evolutionary progression 

from F. nana through F. hurdi to F. nancei is a plausible hypothesis.

DISCUSSION AND SUMMARY

The Miocene turtles from the Calvert Cliffs and nearby areas 

present an interesting blend of genera and species that are extinct 

(Bairdemys miocenica, Trachyaspis lardyi, Procolpochelys grandaeva, Psephophorus polygonus, Hesperotestudo ducateli, Hesperotestudo williamsi, Floridemys hurdi, Floridemys nancei) and 

taxa that represent genera still living in this region (Apalone cf. 

A. ferox, Lepidochelys sp., “Deirochelys” carri, Graptemys sp.,

Chrysemys isoni, Trachemys inflata, Pseudemys caelata, Pseudemys williamsi). It seems likely that a few more genera of nonmarine turtles will show up with future collecting. For example, the 

box turtle Terrapene has been reported in Florida from the Early 

Miocene (Auffenberg, 2001), but it has not shown up in the midAtlantic region. Terrapene is common in the mid-Atlantic region 

today, so it would be strange if it were not also here in the Miocene. Thus, its absence to date likely reflects the general rarity 

of land turtle remains in the Calvert Cliffs, and it may well be 

found in the future. Similarly, on the basis of the tentative Late 

Miocene occurrence of Clemmys in Florida (Auffenberg, 2001), 

it seems likely that the spotted turtle also will eventually show up 

at least in the St. Marys and Yorktown Formations. The absence 

of other modern genera of turtles in the Late Miocene, both in 

the mid-Atlantic region and in Florida, suggests that they were 

not present during the Late Miocene in the Maryland and Virginia regions because those turtles probably did not colonize the 

Atlantic Coast region of America before the Pliocene.

Most striking is the nearly complete turnover of taxa among 

marine turtles. Three of the four Miocene cheloniid taxa (Trachyaspis lardyi, Procolpochelys grandaeva, and the generically 

indeterminate cheloniid) are extinct, along with the only leatherback turtle in this fauna (Psephophorus polygonus). The only 

living cheloniid genus in this fauna (Lepidochelys sp.) does not 

appear until the Late Miocene. The highest occurrences of Procolpochelys grandaeva are in the Little Cove Point Member of 

the St. Marys Formation, and the highest occurrences of Psephophorus polygonus are in the Windmill Point Member of the 

St. Marys Formation. Trachyaspis lardyi persisted well into the 

Early Pliocene in the mid-Atlantic region (Zug, 2001) and into 

the Late Pliocene of Italy (Villa and Raineri, 2015), whereas the 

leatherback genus Psephophorus persisted into the Early Pliocene in Florida. The modern genus Lepidochelys appears in the 
NUMBER 107 • 4 5

local record in the Late Miocene, and by the Early Pliocene, four 

of the five living cheloniid genera (Caretta, Chelonia, Eretmochelys, and Lepidochelys) were present in Florida (Dodd and 

Morgan, 1992). Unfortunately, the very Late Miocene Eastover 

Formation has yielded very sparse marine turtle remains, but 

even so, it is clear from the preserved fossil record that extinction 

and replacement among the marine turtles in the mid-Atlantic 

region of the eastern United States occurred either somewhat 

gradually or in stair-step fashion over Late Miocene and Early 

Pliocene time and not in a single catastrophic extinction and replacement event.

A very different pattern occurred among nonmarine turtles 

(Figure 1.20). Bairdemys miocenica, Hesperotestudo williamsi, 

and Hesperotestudo ducateli have not been found above the 

early Middle Miocene interval. The disappearance of B. miocenica may be real, but Hesperotestudo did not go regionally 

FIGURE 1.20. Chart showing known ranges of turtle taxa identified from the Miocene of the Delaware-MarylandVirginia region (solid lines). Dashed lines show inferred ranges between known ranges. Dashed lines that continue 

to the top of the figure indicate taxa that are known to have persisted more recently than the early Pliocene epoch.

Trachemys is present in the Fairhaven Member, but it is uncertain whether T. inflata is the correct species designation, 

so this interval is queried. Timescale is from Weems et al. (2017).
4 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

extinct at that time. Its continued presence has been documented 

in southern North Carolina in the Early Pliocene (Zug, 2001), 

as well as in the Pleistocene Port Kennedy Cave deposit in Pennsylvania (Parris and Daeschler, 1995) and in the Pleistocene of 

Florida (Hulbert, 2001). The apparent Miocene disappearance 

of these three species in the Maryland and Virginia region probably reflects nothing more than the regional cooling of climate 

in the mid-Atlantic region after the end of the Middle Miocene 

Climatic Optimum, with at least Hesperotestudo returning intermittently during warmer climatic intervals. In all likelihood, the 

“disappearance” of the dwarf barrier island tortoise Floridemys 

hurdi reflects its evolutionary transformation into the slightly 

larger early Late Miocene dwarf barrier island tortoise Floridemys nancei. The extinction of F. nancei, however, does mark the 

last known occurrence of Floridemys and probably documents a 

real extinction event toward the end of the Miocene. In contrast, 

starting in the Late Miocene, Pseudemys caelata and “Deirochelys” carri first appear in the mid-Atlantic region, whereas in 

Florida at about the same time Clemmys possibly appears as well 

(Auffenberg, 2001). It is not until the Pliocene that Chelydra, 

Graptemys, and Malaclemys make their first appearance anywhere in the southeastern United States (Hulbert, 2001). Therefore, the evolutionary change in the nonmarine turtle fauna in 

the mid-Atlantic region mostly appears to represent an expansion and diversification of the turtle fauna without any major 

extinction events among this group. 

Sea turtle remains come from nearly all portions of the Calvert, Choptank, and St. Marys Formations (Figure 1.20), but 

nonmarine turtle remains are largely concentrated in three stratigraphic intervals. One is low in the Fairhaven Member of the 

Calvert Formation at the Pollack Farm site in Delaware, in the 

Popes Creek Sand Bed in the Popes Creek bluffs in Maryland, 

and along the Pamunkey River at a horizon equivalent to the 

Popes Creek Sand Bed. The second interval is in SZ 10 and the 

immediately overlying basal SZ 11 of the Plum Point Member of 

the Calvert Formation in the Calvert Cliffs. The third interval is 

in the Little Cove Point Member of the St. Marys Formation near 

Chesapeake Ranch Estates. In all of these cases, it seems likely 

that either these units were deposited in exceptionally nearshore 

and shallow marine waters and/or there was a major river carrying turtle carcasses into the area where their remains have been 

found in exceptional abundance. Even so, although most of the 

nonmarine turtle remains have shown up at these three horizons, 

occasional nonmarine turtle remains do show up at other stratigraphic horizons. A good example is the discovery of a largely 

complete shell of Chrysemys isoni in SZ 12. 

ACKNOWLEDGMENTS

I thank Brenna Litynski for the many turtle illustrations that she prepared for this chapter, Tim Scheirer for his illustration of Dermochelys, Colleen Lodge for providing me 

with her drawing of the Calvert Psephophorus humerus 

(Figure 1.15H), and Stephen J. Godfrey for providing many of 

the photographs of turtle specimens used in this chapter. I also 

thank Gary Grimsley, Natasha Vitek, and an anonymous reviewer 

for thoroughly reviewing and offering significant improvements to 

this chapter. Finally, I thank the many volunteer collectors whose 

diligence in finding and recovering the material described here 

has made possible a detailed understanding of the Miocene turtle 

fauna that once existed in the Calvert Cliffs region.

REFERENCES

Auffenberg, W. 1963. Fossil Testudinine Turtles of Florida. Genera Geochelone

and Floridemys. Bulletin of the Florida State Museum, Biological Sciences, 

7(2):53–97.

Auffenberg, W. 1964. A New Fossil Tortoise from the Texas Miocene, with Remarks on the Probable Geologic History of Tortoises in Eastern U.S. PearceSellards Series, 3:1–11.

Auffenberg, W. 1974. Checklist of Fossil Land Tortoises (Testudinidae). Bulletin of 

the Florida State Museum of Biological Sciences, 18(3):121–251.

Auffenberg, W. 2001. Turtles and Tortoises. In The Fossil Vertebrates of Florida, 

ed. R. C. Hulbert Jr., pp. 118–136. Gainesville: University Press of Florida.

Berry, C. T., and W. G. Lynn. 1936. A New Turtle, Peritresius virginianus, from 

the Miocene of Virginia. Proceedings of the American Philosophical Society, 

76:175–190. 

Boulenger, G. A. 1889. Catalogue of the Chelonians, Rhynchocephalians, and 

Crocodiles in the British Museum (Natural History), by Order of the Trustees. London: Taylor and Francis.

Bourque, J. R. 2015. New Mud Turtles (Kinosternidae, Kinosternon) from the Middle-Late Miocene of the United States. Journal of Paleontology, 89(5):821–

844. https://doi.org/10.1017/jpa.2015.63

Bourque, J. R. 2016. Side-Necked Turtles (Testudines, Pleurodira) from the Ancient Gulf Coastal Plain of Florida during Middle Cenozoic Megathermals. 

Chelonian Conservation and Biology, 15(1):23–35. https://doi.org/10.2744/

CCB-1159.1

Bourque, J. R., and B. W. Schubert. 2015. Fossil Musk Turtles (Kinosternidae, Sternotherus) from the Late Miocene–Early Pliocene (Hemphillian) of Tennessee 

and Florida. Journal of Vertebrate Paleontology, 35 (1):e885441. https://doi.

org/10.1080/02724634.2014.885441

Case, E. C. 1904. Reptilia. In The Miocene, ed. W. B. Clark, G. B. Shattuck, and W. 

H. Dall, pp. 62–70. Baltimore: Johns Hopkins Press.

Chesi, F., M. Delfino, A. Varola, and L. Rook. 2007. Fossil Sea Turtles (Chelonii, 

Dermochelyidae and Cheloniidae) from the Miocene of Pietra Leccese (Late 

Burdigalian-Early Messinian), Southern Italy. Geodiversitas, 29(2):321–333.

Clark, J., J. R. Beerbower, and K. K. Kietzke, 1967. Oligocene Sedimentation, 

Stratigraphy, Paleoecology and Paleoclimatology in the Big Badlands of 

South Dakota. Fieldiana, Geology Memoirs, 5. https://doi.org/10.5962/bhl.

title.3290

Collins, R. L., and W. G. Lynn. 1936. Fossil Turtles from Maryland. Proceedings of 

the American Philosophical Society, 76:151–173.

Cope, E. D. 1867. An Addition to the Vertebrate Fauna of the Miocene Period, 

with a Synopsis of the Extinct Cetacea of the United States. Proceedings of 

the Philadelphia Academy of Natural Sciences, 19:143.

Cope, E. D. 1869a. Third Contribution to the Fauna of the Miocene Period of the 

United States. Proceedings of the Philadelphia National Academy of Sciences, 

21:6–12.

Cope, E. D. 1869b. The Fossil Reptiles of New Jersey (Continued). American Naturalist, 3(2):84–91. https://doi.org/10.1086/270371

Cope, E. D. 1869c. Synopsis of the Extinct Batrachia, Reptiles, and Aves of North 

America. Transactions of the American Philosophical Society, 14:1–252. 

https://doi.org/10.2307/1005355

Cope, E. D. 1896. Sixth Contribution to the Knowledge of the Marine Miocene 

Fauna of North America. Proceedings of the American Philosophical Society, 

35:138–156.

Costa, O. G. 1851. Cenni intorno alle scoperte fatte nel Regno riguardanti la paleontologia nel corso dell’anno 1851. Letti all’Accademia Pontaniana nella 

tornata del 31 agosto 1851. Naples, Italy: Filiatre Sebezio. 
NUMBER 107 • 4 7

Costa, O. G. 1864. Paleontologia del Regno di Napoli, III. Atti dell’Accademia 

Pontaniana, 8:1–198.

Delfino, M., T. M. Scheyer, F. Chesi, and S. W. Salisbury. 2013. Gross Morphology and Microstructure of Type Locality Ossicles of Psephophorus polygonus Meyer, 1847 (Testudines, Dermochelyidae). Geological Magazine, 

150(5):767–782. https://doi.org/10.1017/S001675681200091X

Delfortrie, E. 1869. Les Chéloniens du Miocène Supérieur de la Gironde. Actes de 

la Société linnéenne de Bordeaux, 27:399–424.

Dodd, C. K., and G. S. Morgan. 1992. Fossil Sea Turtles from the Early Pliocene 

Bone Valley Formation, Central Florida. Journal of Herpetology, 26(1):1–8. 

https://doi.org/10.2307/1565014

Ehret, D. J., and J. R. Bourque. 2011. An Extinct Map Turtle Graptemys (Testudines, 

Emydidae) from the Late Pleistocene of Florida. Journal of Vertebrate Paleontology, 31(3):575–587. https://doi.org/10.1080/02724634.2011.562267

Ferreira, G. S., A. D. Rincón, A. Solórzano, and M. C. Langer. 2015. The Last 

Marine Pelomedusoids (Testudines: Pleurodira): a New Species of Bairdemys

and the Paleoecology of Stereogenyina. PeerJ, 3: e1063.

Frazier, J. G., V. Azzarà, O. Munoz, L. G. Marcucci, E. Badel, F. Genchi, M. Cattani, M. Tosi, and M. Delfino. 2018. Remains of Leatherback Turtles, Dermochelys coriacea, at Mid-Late Holocene Archaeological Sites in Coastal Oman: 

Clues of Past Worlds. PeerJ, 6:e6123. https://doi.org/10.7717/peerj.6123

Gaffney, E. S., and R. Zangerl. 1968. A Revision of the Chelonian Genus Bothremys (Pleurodira: Pelomedusidae). Fieldiana, Geology, 16(7):193–239. 

https://doi.org/10.5962/bhl.title.5195

Gaffney, E. S., H. Tong, and P. A. Meylan. 2006. Evolution of the Side-Necked 

Turtles: The Families Bothremydidae, Euraxemydidae, and Araripemydidae. 

Bulletin of the American Museum of Natural History, 300:1–698. https://doi.

org/10.1206/0003-0090(2006)300[1:EOTSTT]2.0.CO;2

Gibson, T. G. 1983. Stratigraphy of Miocene through Lower Pleistocene Strata of 

the United States Central Atlantic Coastal Plain. In Geology and Paleontology of the Lee Creek Mine, North Carolina, I, ed. C. E. Ray, pp. 35–80. 

Smithsonian Contributions to Paleobiology 53. Washington, D.C.: Smithsonian Institution Press.

Hasegawa, Y., R. Hirayama, T. Kimura, Y. Takakuwa, and H. Nakajima. 2005. 

Skeletal Restoration of a Fossil Sea Turtle, Syllomus, from the Middle Miocene Haratajino Formation, Tomioka Group, Gunma Prefecture, Central Japan. Bulletin of the Gunma Museum of Natural History, 9:29–64.

Hay, O. P. 1908. Fossil Turtles of North America. Carnegie Institute of Washington 

Publication 75. Washington, D.C.: Carnegie Institute of Washington.

Hay, O. P. 1916. Descriptions of some Floridian Fossil Vertebrates, Belonging Mostly to 

the Pleistocene. Annual Report of the Florida State Geological Survey, 8:39–76.

Holman, J. A. 1998. Reptiles of the Lower Miocene (Hemingfordian) Pollack Farm 

Fossil Site, Delaware. In Geology and Paleontology of the Lower Miocene 

Pollack Farm Fossil Site, Delaware, ed. R. N. Benson. Delaware Geological 

Survey Special Publication, 21:141–147. 

Holman, J. A., and D. Parmley. 2005. Noteworthy Turtle Remains from the Late 

Miocene (Late Hemphillian) of Northeastern Nebraska. Texas Journal of Science, 57(4):307–316.

Hulbert, R. C., Jr. 2001. The Fossil Vertebrates of Florida. Gainesville: University 

Press of Florida.

Hummel, K. A. 1932. Fossilium catalogus, I: Animalia. Part 52: Trionychia fossilia. 

Berlin: W. Junk.

Jackson, D. R. 1975. A Pleistocene Graptemys (Reptilia: Testudines) from the 

Santa Fe River of Florida. Herpetologica, 31(2):213–219.

Jackson, D. R. 1976. The Status of the Pliocene Turtles Pseudemys caelata Hay 

and Chrysemys carri Rose and Weaver. Copeia, 1976(4):655–659. https://

doi.org/10.2307/1443445

Jackson, D. R. 1978. Evolution and Fossil Record of the Chicken Turtle Deirochelys, with a Re-evaluation of the Genus. Tulane Studies in Zoology and 

Botany, 20:35–55.

Johnson, G. H., and L. W. Ward. 1990. Cenozoic Stratigraphy across the Fall Zone 

and Western Coastal Plain, Southern Virginia: A Field Guidebook. Richmond, Va.: Virginia Geological Field Conference.

Joyce, W. G., and J. R. Bourque. 2016. A Review of the Fossil Record of Turtles of 

the Clade Pan-Kinosternoidea. Bulletin of the Peabody Museum of Natural 

History, 57:57–95. https://doi.org/10.3374/014.057.0104

Kuhn, O. 1964. Fossilium Catalogus, I: Animalia. Part 107: Testudines. The 

Hague, Netherlands: W. Junk.

Lapparent de Broin, F. de. 2001. The European Turtle Fauna from the Triassic to 

the Present. Dumerilia, 4:155–218.

Leidy, J. 1851. Several Fossils from the Greensand of New Jersey. Proceedings of 

the Academy of Natural Sciences of Philadelphia, 5:329–330.

Lydekker, R. 1889. Catalogue of the Fossil Reptilia and Amphibia in the British 

Museum. Part 3: Chelonia. London: British Museum (Natural History).

Maryland Department of Natural Resources. 2023. Maryland’s Turtles & Tortoises 

(Order Testudines). https://dnr.maryland.gov/wildlife/Pages/plants_wildlife/

herps/FieldGuide_OrderTestudines.aspx (accessed 14 March 2023). 

Meyer, H. V. 1843. Mittheilungen an Prof. Bronn gerichtet. Neues Jahrbuch für 

Mineralogie, Geognosie, Geologie und Petrefaktenkunden, Briefwechsel, 

1843:698–704.

Meyer, H. von. 1847. Mittheilungen an Professor Bronn gerichtet. Neues 

Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefaktenkunde 

1847:572–581.

Meylan, P. A. 1987. The Phylogenetic Relationships of Soft-Shelled Turtles (Family Trionychidae). Bulletin of the American Museum of Natural History, 

186:1–101.

Meylan, P. A., and W. Sterrer. 2000. Hesperotestudo (Testudines: Testudinidae) 

from the Pleistocene of Bermuda, with Comments on the Phylogenetic Position of the Genus. Zoological Journal of the Linnean Society, 128(1):51–76. 

https://doi.org/10.1111/j.1096-3642.2000.tb00649.x

Misuri, A. 1911. Sopra un nuovo trionichide dell’arenaria miocenica del Bellunese 

(Trionyx bellunensis Dal Piaz in sch.). Perugia, Italy: Sab. Tip. V. Bartelli.

Palmer, W. 1908. Description of a New Species of Leatherback Turtle from the 

Miocene of Maryland. Proceedings of the United States National Museum, 

36(1669):369–373. https://doi.org/10.5479/si.00963801.36-1669.369

Parmalee, P. W., W. E. Klippel, P. A. Meylan, and J. A. Holman. 2002. A Late Miocene-Early Pliocene Population of Trachemys (Testudines, Emydidae) from 

East Tennessee. Annals of the Carnegie Museum, 71(4):233–239. https://doi.

org/10.5962/p.329869

Parris, D. C., and E. Daeschler. 1995. Pleistocene Turtles of Port Kennedy Cave 

(Late Irvingtonian), Montgomery County, Pennsylvania. Journal of Paleontology, 69(3):563–568. https://doi.org/10.1017/S0022336000034934

Powars, D. S., and T. S. Bruce. 1999. The Effects of the Chesapeake Bay Impact 

Crater on the Geological Framework and Correlation of Hydrogeologic 

Units of the Lower York-James Peninsula, Virginia. U.S. Geological Survey 

Professional Paper, 1612:1–82. https://doi.org/10.3133/pp1612

Rose, F. L., and W. G. Weaver. 1966. Two New Species of Chrysemys (= Pseudemys) from the Florida Pliocene. Tulane Studies in Geology and Paleontology, 5:41–48.

Shattuck, G. B. 1904. Geological and Paleontological Relations, with a Review of 

Earlier Investigations. In The Miocene Deposits of Maryland, ed. W. B. Clark, 

G. B. Shattuck, and W. H. Dall, pp. xxxiii–cxxxvii. Baltimore: Johns Hopkins 

Press. [Reprinted 1973.]

Shikama, T. 1956. Miocene Chelonia of Japan. Yokohama National University, 

Science Reports Section 2, 5:35–62.

Spamer, E. E., E. Daeschler, and L. G. Vostreys-Shapiro. 1995. A Study of Fossil 

Vertebrate Types in the Academy of Natural Sciences of Philadelphia. Academy of Natural Sciences of Philadelphia Special Publication, 16:1–435.

The Fossil Forum. 2016. Jaw bone? Armour plate? http://www.thefossilforum.

com/index.php?/topic/68389-jaw-bone-armour-plate/ (accessed 21 March 

2023).

Villa, A., and G. Raineri. 2015. The Geologically Youngest Remains of Trachyaspis lardyi Meyer, 1843 (Testudines, Cheloniidae): A New Specimen from the 

Late Pliocene of the Stirone River (Northern Italy). Bollettino della Societa 

Paleontologica Italiana, 54(2):117–124.

Virginia Herpetological Society. 2023. https://www.virginiaherpetologicalsociety.

com/ (accessed 3 May 2023).

Vitek, N. S., and W. G. Joyce. 2015. A Review of the Fossil Record of New World 

Turtles of the Clade Pan-Trionychidae. Bulletin of the Peabody Museum of 

Natural History, 56:185–244. https://doi.org/10.3374/014.056.0204

Vlachos, E. 2018. A Review of the Fossil Record of North American Turtles of the 

Clade Pan-Testudinoidea. Bulletin of the Peabody Museum of Natural History, 59:3–94. https://doi.org/10.3374/014.059.0101

Weaver, W. G., Jr., and J. S. Robertson. 1967. A Re-evaluation of Fossil Turtles of 

the Chrysemys scripta Group. Tulane Studies in Geology, 5(2):53–66.

Weems, R. E. 1974. Middle Miocene Sea Turtles (Syllomus, Procolpochelys, 

Psephophorus) from the Calvert Formation. Journal of Paleontology, 

48(2):278–303.

Weems, R. E. 1980. Syllomus aegyptiacus, a Miocene Pseudodont Sea Turtle. Copeia, 1980(4):621–625. https://doi.org/10.2307/1444438
4 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Weems, R. E., and K. M. Brown. 2017. More-Complete Remains of Procolpochelys 

charlestonensis (Oligocene, South Carolina), an Occurrence of Euclastes (Upper Eocene, South Carolina), and Their Bearing on Cenozoic Pancheloniid 

Sea Turtle Distribution and Phylogeny. Journal of Paleontology, 91(6):1228–

1243. https://doi.org/10.1017/jpa.2017.64

Weems, R. E., and L. E. Edwards. 2007. The Age and Provenance of “Eschrichtius” cephalus Cope (Mammalia: Cetacea). Journal of Vertebrate Paleontology, 27(3):752–756. https://doi.org/10.1671/0272-4634(2007)27[752:TAAP

OE]2.0.CO;2

Weems, R. E., L. E. Edwards, and B. Landacre. 2017. Geology and Biostratigraphy of the Potomac River Cliffs at Stratford Hall, Westmoreland County, 

Virginia. In From the Blue Ridge to the Beach: Geological Field Excursions 

across Virginia, ed. C. M. Bailey and S. Jaye, pp. 125–152. Geological Society 

of America Field Guide 47. Boulder, Colo.: Geological Society of America. 

https://doi.org/10.1130/2017.0047(05)

Weems, R. E., and R. A. George. 2013. Amphibians and Nonmarine Turtles from 

the Miocene Calvert Formation of Delaware, Maryland, and Virginia (USA). 

Journal of Paleontology, 87(4):570–588. https://doi.org/10.1666/12-071

Weems, R. E., and R. A. George. 2014. Erratum to Amphibians and Nonmarine Turtles from the Miocene Calvert Formation of Delaware, Maryland, and Virginia (USA). Journal of Paleontology, 88(1):204. https://doi.

org/10.1666/12-071.1

Weems, R. E., and J. L. Knight. 2012. A New Species of Bairdemys (Pelomedusoides: Podocnemididae) from the Oligocene (Early Chattian) Chandler Bridge 

Formation of South Carolina, U.S.A., and Its Paleobiogeographic Implications for the Genus. In Morphology and Evolution of Turtles, ed. D. B. 

Brinkman, P. Holroyd, and J. Gardner, pp. 289–303. Vertebrate Paleobiology 

and Paleoanthropology Series. Dordrecht, Netherlands: Springer. https://doi.

org/10.1007/978-94-007-4309-0_18

Weems, R. E., and A. E. Sanders. 2014. Oligocene Pancheloniid Sea Turtles from 

the Vicinity of Charleston, South Carolina, U.S.A. Journal of Vertebrate Paleontology, 34(1):80–99. https://doi.org/10.1080/02724634.2013.792826

Williams, E. E., 1950. Testudo cubensis and the Evolution of Western Hemisphere 

Tortoises. American Museum of Natural History Bulletin, 91(1):1–36.

Wood, R. C., J. Johnson-Gove, E. S. Gaffney, and K. F. Maley. 1996. Evolution 

and Phylogeny of Leatherback Turtles (Dermochelyidae), with Descriptions 

of New Fossil Taxa. Chelonian Conservation and Biology, 2(2):266–286.

Zangerl, R. 1958. De oligozänen Meerschildkröten von Glarus. Schweizerische Paläontologische Abhandlungen, 73:1–56, 15 plates.

Zangerl, R., and W. D. Turnbull. 1955. Procolpochelys grandaeva (Leidy), an 

Early Carettine Sea Turtle. Fieldiana, Zoology, 37:345–382. https://doi.

org/10.5962/bhl.title.3230

Zug, G. R. 2001. Turtles of the Lee Creek Mine (Pliocene: North Carolina). In 

Geology and Paleontology of the Lee Creek Mine, North Carolina, III, ed. 

C. E. Ray and D. J. Bohaska, pp. 219–225. Smithsonian Contributions to 

Paleobiology 90. Washington, D.C.: Smithsonian Institution Press.
ABSTRACT. A taxonomically diverse toothed whale (Cetacea, Odontoceti) fauna 

of 29 named species is known from along the Calvert Cliffs and other Miocene age 

deposits (Chesapeake Group) within the Chesapeake Bay region (Atlantic Coastal Plain, 

Maryland and Virginia, USA). They range in age from approximately 22 to 8 Ma and 

derive from the Calvert, Choptank, and St. Marys Formations. Representatives of the following families are known: Squalodontidae, Physeteridae, Ziphiidae, Squalodelphinidae, 

Platanistidae, Eurhinodelphinidae, Kentriodontidae, Pontoporiidae, and basal delphinidans formerly placed within Kentriodontidae. Four of these families have living representatives: Physeteridae, Ziphiidae, Platanistidae, and Pontoporiidae. Squalodontidae 

is represented by three species: Squalodon calvertensis, S. whitmorei, and S. murdochi

sp. nov. Physeteridae includes Orycterocetus crocodilinus and “Aulophyseter” mediatlanticus. Ziphiidae includes two unnamed species: cf. Messapicetus sp. and Ziphiidae 

incertae sedis. Squalodelphinidae is known by at least two species: Phocageneus venustus

and an undetermined species. Platanistidae is represented by five species: Araeodelphis 

natator, Grimadelphis spectorum gen. et sp. nov., Zarhachis flagellator, Pomatodelphis 

inaequalis, and Pomatodelphis santamaria sp. nov. Eurhinodelphinidae features at least 

four species: Xiphiacetus bossi, X. cristatus, Schizodelphis barnesi, and S. morckhoviensis. Kentriodontidae includes Kentriodon pernix. Other Miocene delphinidans (most 

of which have previously been included within the Kentriodontidae) include Brevirostrodelphis dividum (new combination), Hadrodelphis calvertense, Macrokentriodon 

morani, Miminiacetus pappus (new combination), Pithanodelphis cornutus (recognized 

here from the Atlantic Coastal Plain for the first time), Lophocetus calvertensis, and four 

new delphinidans: Herbeinodelphis nancei gen. et sp. nov., Cammackacetus hazenorum

gen. et sp. nov., Pictodelphis kidwellae gen. et sp. nov., and Westmorelandelphis tacheroni

gen. et sp. nov. Pontoporiidae is represented by a single named species, Stenasodelphis 

russellae. Odontoceti incertae sedis includes a Chilcacetus-grade odontocete, Caolodelphis

2 Miocene Toothed Whales 

(Odontoceti) from Calvert 

Cliffs, Atlantic Coastal 

Plain, USA

Stephen J. Godfrey1,2* and 

Olivier Lambert3

1 Curator of Paleontology, Department of Paleontology, Calvert Marine Museum, P.O. Box 

97, Solomons, Maryland, 20688, USA.

2 Research Associate, Department of Paleobiology, National Museum of Natural History, 

Smithsonian Institution, Washington, D.C. 

20013-7012, USA.

3 Unité de Recherche Evolution de la Paléobiosphère, D.O. Terre et Histoire de la Vie, Institut 

royal des Sciences naturelles de Belgique, Rue 

Vautier, 29, 1000 Brussels, Belgium.

*Correspondence: 

Stephen.Godfrey@calvertcountymd.gov

Received 7 May 2020; accepted 15 December 

2022.
5 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

milleri gen. et sp. nov., the puzzling Enigmatocetus posidoni

gen. et sp. nov., and other partial skulls. Sixty-two percent of the 

Miocene odontocetes from Maryland and Virginia are endemic 

to this region, and 83% are known only from the western North 

Atlantic. In terms of their chronostratigraphic distribution, collectively, they range in age from Aquitanian through Tortonian, 

with the large majority occurring within the Burdigalian, Langhian, and Serravallian stages.

INTRODUCTION

Calvert Cliffs and other Miocene exposures (outcrop belts) 

along tributaries to the Chesapeake Bay in the states of Maryland and Virginia preserve one of the most abundant and diverse 

assemblages of extinct toothed whales (Odontoceti). In terms of 

its taxonomic diversity and numbers of known specimens, it rivals the odontocete faunas in the Pisco and Sacaco Basins in Peru 

(Muizon, 1984, 1988b; Muizon and Domning, 2002; Bianucci 

et al., 2010, 2016b, 2016c, 2020; Lambert et al., 2014, 2017a, 

2017c; Di Celma et al., 2019), the Antwerp area in Belgium (Abel, 

1901, 1902, 1905; Lambert, 2005a, 2005b, 2005c, 2008; Colpaert et al., 2015), the Belluno Sandstone (Dal Piaz, 1916; Pilleri, 

1985) and other localities in Italy (Bianucci, 1997, 2001, 2013; 

Bianucci and Landini, 2002), Mexico (Barnes, 1984, 1992, 1998, 

2002, 2008; Aguirre-Fernández et al., 2009), and other localities 

in the United States, such as the Miocene Pungo River Formation from the Aurora Phosphate Mine (formerly known as the Lee 

Creek Mine) in Aurora, Beaufort County, North Carolina (Whitmore and Kaltenbach, 2008); the Sharktooth Hill Bone Bed and 

other localities of California (Kellogg, 1931; Wilson, 1935; Barnes 

and Mitchell, 1984; Pyenson et al., 2009, and references therein); 

and the Pollack Farm site in Delaware (Bohaska, 1998).

At least eight families are represented in the Miocene portion of the Chesapeake Group: Squalodontidae, Physeteridae, 

Ziphiidae, Squalodelphinidae, Platanistidae, Eurhinodelphinidae, Kentriodontidae, and Pontoporiidae. All of the known 

odontocete genera and species are extinct, and only four of these 

families have living representatives: Physeteridae (sperm whales), 

Ziphiidae (beaked whales), Platanistidae (South Asian river dolphins) and Pontoporiidae (the La Plata dolphin). Eurhinodelphinids are the most commonly encountered odontocetes along 

Calvert Cliffs, squalodontids are the most archaic looking, and 

physeterids are collectively the largest (a few large teeth suggest 

the presence of at least one very large physeteroid). Squalodelphinids, ziphiids, and pontoporiids are known only from a few 

incomplete skulls, so much remains to be learned by future discoveries and the restudy of existing specimens.

History of Research

When Richard Harlan described the partial skull of Delphinus calvertensis in 1842, he became the first paleontologist 

to name a fossil odontocete from the Chesapeake Group. Later, 

Cope (1868) reassigned this specimen to the genus Lophocetus, 

as it is presently known. Testament to the rarity of many of the 

Chesapeake Group odontocete taxa is the fact that more than 

150 years would pass before even a small portion of a second 

skull of L. calvertensis would be found. Following in the footsteps of Harlan, other paleontologists, including Cope (1866, 

1867, 1868, 1869, 1895), Leidy (1869, 1877), Gill (1871), 

Hay (1902), Case (1904), Eastman (1906, 1907), True (1908a, 

1908b, 1912), Kellogg (1923a, 1924a, 1924b, 1925a, 1926, 

1927a, 1955, 1957, 1959, 1965, 1966), Whitmore (1971, 

1984), Barnes (1978), Muizon (1987, 1988a), Dawson (1996a, 

1996b), Dooley (2003, 2005), Lambert (2004, 2005a), Fuller 

and Godfrey (2007), Godfrey and Barnes (2008), Gerholdt 

and Godfrey (2010), Lambert et al. (2010b), and Godfrey et 

al. (2017), have described or reviewed odontocetes from the 

Chesapeake Group. The most recent comprehensive review of 

Miocene cetaceans was completed by Gottfried et al. (1994) 

and provided a very helpful guide to the diversity and stratigraphic distribution of the then known taxa, their temporal 

trends, and a comparison with modern cetacean assemblages. 

Gottfried et al. concluded that cetaceans were most abundant 

and diverse in the upper third of the Calvert Formation, with 

the fauna dominated by longirostrine eurhinodelphinids. In 

terms of odontocetes, the Miocene Chesapeake Group differs 

from the Holocene northwestern Atlantic most conspicuously 

in the absence of delphinids and phocoenids (Gottfried et al., 

1994; Whitmore, 1994).

Many early holotypes, particularly those identified by Cope, 

are based on isolated vertebrae and teeth from New Jersey, 

Maryland, and Virginia. Kellogg, in particular, held up publication on skulls and mandibles while attempting to identify these 

types from specimens with associated vertebrae and skulls, with 

mixed results. In some cases, Kellogg’s referred specimens have 

become the de facto types, although no formal petitions following the International Code of Zoological Nomenclature have 

been made. In ideal circumstances, more complete skeletons 

would allow identification of Cope’s and others’ types or show 

that two or more taxa had identical elements, allowing formal 

designation of nomen dubia. In practice, many early types have 

simply been ignored, as they are here. To further delay studies of 

these important faunas over nomenclatural problems would be a 

disservice, and both science and nomenclature change over time 

anyway (D. Bohaska, National Museum of Natural History, personal communication, 1 March 2022).

The intent of this review is to provide a current taxonomic 

and illustrated catalog of Miocene odontocetes from the Calvert, Choptank, and St. Marys Formations (Figure 2.1). It is beyond the scope of this work to review the odontocete remains 

from other Chesapeake Group formations (the Oligocene Old 

Church Formation, the Upper Miocene Eastover Formation, and 

the Pliocene Yorktown and Chowan River Formations). Furthermore, given time and space constraints, it was impossible to fully 

describe and exhaustively illustrate every species; that would necessitate a much longer work. Nevertheless, we hope that this 
NUMBER 107 • 51

FIGURE 2.1. Miocene stratigraphy in the area of Calvert Cliffs. The “Popes Creek Sand” is not a formal Shattuck-Zone, 

but rather the current name given to this unnumbered unit (see Shattuck, 1904; Kidwell et al., 2015).
5 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

effort will constitute a reference and identification guide providing quick access to original-source literature for greater details 

on the morphology and systematics of these extinct odontocetes. 

Some stones have been left unturned: some fragmentary specimens remain unnamed, and there are additional taxonomically 

unidentified isolated cranial elements, teeth, and periotics that 

hint at even greater diversity. Amateur and avocational paleontologists should not get the impression that this is the final word 

on fossil odontocetes from Calvert Cliffs. Rather, we hope that 

this chapter will prompt inquisitive collectors to show unusual 

specimens to experts because both they and the professional contribute to the advancement of our understanding of the evolution 

of life on Earth.

MATERIAL AND METHODS

Anatomical Terminology and Illustrations

The identification of morphological features for odontocete 

skulls follows Mead and Fordyce (2009). Images of the crania 

were made with the axis of the rostrum in a horizontal plane.

Geological Context

Geologic ages and terminology for Chesapeake Group stratigraphy generally follow Kidwell et al. (2015). Shattuck-Zones 

are included where known for all referred specimens. ShattuckZones are informal lithologic units established by Shattuck (1904) 

that are still very useful for identifying and localizing the occurrence of fossils within the Calvert Cliffs (Kidwell et al., 2015).

Systematics and Taxonomy

Two higher-rank clades, Platanistoidea and Kentriodontidae, deserve some comments here because their content is still 

debated. Containing only one modern genus, Platanista, the 

superfamily Platanistoidea is mostly composed of extinct taxa. 

Whereas several families have consistently been recovered as 

belonging to Platanistoidea in recent analyses (Platanistidae, 

Squalodelphinidae, and, in a smaller number of studies, Allodelphinidae), other taxa (e.g., Prosqualodon, Squalodontidae, and Waipatiidae) are recovered in this superfamily in only 

some of the analyses (e.g., Muizon, 1987, 1991, 1994; Fordyce, 

1994; Tanaka and Fordyce, 2016, 2017; Tanaka et al., 2017; 

Lambert et al., 2017c; Bianucci et al., 2018, 2020). Because 

of this lack of consensus, restricting the content of the superfamily to the families Platanistidae, Squalodelphinidae, and 

Allodelphinidae was recently proposed (Bianucci et al., 2020). 

According to this last work, we also use the lower-rank clade 

Platanidelphidi, comprising the extant Platanista and all species that share a more recent common ancestor with Platanista

than with Allodelphis.

Within the infraorder Delphinida, including the modern 

clades Lipotidae, Inioidea (Iniidae + Pontoporiidae), and Delphinoidea (Delphinidae + Monodontidae + Phocoenidae), the extinct 

family Kentriodontidae in its original definition (see Barnes, 1978; 

Muizon, 1988c) has proven nonmonophyletic in several recent 

analyses, with members of the group either being recovered as 

stem delphinidans or stem delphinoids or being even more closely 

related to lipotids and inioids (e.g., Lambert et al., 2017b, 2018; 

Peredo et al., 2018b; Kimura and Hasegawa, 2019; but see Guo 

and Kohno, 2021). As a consequence, the clade Kentriodontidae is 

restricted to a smaller number of taxa (in some cases only species 

of the genus Kentriodon), varying from one analysis to the other. 

Pending better-settled relationships of kentriodontids with other 

delphinidans, we prefer to treat most of them as early delphinidans, without family assignation, except for Kentriodon, which is 

the type genus of the family Kentriodontidae.

At a lower taxonomic rank, we provide here only diagnoses 

for new taxa and a few previously defined taxa. Nevertheless, in 

the corresponding sections, references are included for previous 

works in which diagnostic characters are given for the taxon in 

question.

Phylogenetic Relationships

Because of (1) the relatively large number of new species 

described here, (2) their placement in a wide range of higherrank clades (from Squalodon to early delphinidans), and (3) the 

lack of a general odontocete phylogeny providing convincing results among and within all the main subclades, we decided not 

to perform any phylogenetic analyses, also allowing us to keep 

this work to a reasonable length. For specific taxa, we briefly 

comment on previous phylogenetic analyses. We acknowledge 

that for all new species diagnosed here, phylogenetic relationships should be tested, and we hope this testing will be done in 

the near future, focusing on each subclade (e.g., Squalodontidae, 

Platanistoidea, and early Delphinida). Perhaps these studies will 

confirm our systematic attributions and provide additional diagnostic features for these new species.

Whitening of Fossils

Many dark-colored fossils were whitened by dusting them 

with sublimed ammonium chloride, as indicated in their respective figure captions. This is a whitening technique described by 

Cooper (1935) and Feldman (1989). After the specimen was 

photographed with a Nikon CoolPix P510 camera under fluorescent light, the ammonium chloride was removed by holding the 

fossil under running water (Shelburne and Thompson, 2016). As 

a cautionary note, specimens dusted with ammonium chloride 

need to be stable enough to withstand a freshwater rinse because 

without that, a residue of hydrochloric acid would possibly 

remain on the specimen (D. Bohaska, National Museum of Natural History, personal communication, 2022).
NUMBER 107 • 5 3

Abbreviations

Institutional Abbreviations

ANSP Academy of Natural Sciences of Drexel University, 

Philadelphia, Pennsylvania, USA

CMM-V fossil vertebrate collection, Calvert Marine Museum, 

Solomons, Maryland, USA

IRSNB M fossil mammal collection of types and illustrated 

specimens, Institut royal des Sciences naturelles 

de Belgique, Brussels, Belgium

LACM Department of Vertebrate Paleontology, Natural 

History Museum of Los Angeles County, Los Angeles, California, USA

MCZ Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA

MNHN Muséum National d’Histoire Naturelle, Paris, France

USNM Department of Paleobiology, National Museum of 

Natural History (formerly U.S. National Museum), 

Smithsonian Institution, Washington, D.C., USA

Other Abbreviations

ICZN International Code of Zoological Nomenclature

SZ Shattuck-Zone

SYSTEMATIC PALEONTOLOGY

Cetacea Brisson, 1762

Unranked Clade Pelagiceti Uhen, 2008a

Unranked Clade Neoceti Fordyce and Muizon, 2003

Suborder Odontoceti Flower, 1867

Family Squalodontidae Brandt, 1873

Morphologically, the so-called shark-toothed whales (the 

Squalodontidae) represent the most archaic-looking group of 

toothed whales from the Calvert Cliffs. This family displays 

features typically associated with geologically older cetaceans, 

such as heterodonty and all the features associated with the 

ability to detect airborne odors (nasal turbinates, perforate 

cribriform plate, and large olfactory bulb recesses; Godfrey, 

2013). Squalodontid teeth along Calvert Cliffs are easily recognizable by their overall shape and their wrinkled enameled 

crown (Figure 2.2C–F). Squalodontids are one of the geologically youngest odontocete clades to display heterodonty; 

apart from a few, poorly known early Miocene taxa (e.g., Inticetus, Neosqualodon, and Prosqualodon; Lydekker, 1893; 

Dal Piaz, 1904; Lambert et al., 2017c), all other Miocene to 

Holocene odontocetes are roughly homodont (Marx et al., 

2016; although the posteriormost teeth in Inia are sufficiently 

different to be classified as heterodont). In spite of their retention of an archaic dentition (but see Peredo et al., 2018a, 

for an alternative interpretation), squalodontid skulls are fully 

telescoped (see Churchill et al., 2018); that is, the bones surrounding the bony nares (the frontals, maxillae, premaxillae, 

nasals, and presphenoid) have shifted toward the back of the 

skull to abut the supraoccipital, excluding the parietals from 

expression on the dorsal surface of the skull.

Two squalodontids were recognized in the Maryland 

Miocene by Kellogg (1923a), Dooley (2003, 2005), and Whitmore and Kaltenbach (2008): Squalodon calvertensis Kellogg, 

1923 and Squalodon whitmorei Dooley, 2005. We recognize a third species from the Chesapeake Group, Squalodon 

murdochi sp. nov.

Genus Squalodon Grateloup, 1840

Type Species. Squalodon grateloupii von Meyer, 1843 

(see Marx et al., 2011).

Remarks. The family Squalodontidae and the genus 

Squalodon have long been used as wastebaskets for fragmentarily known odontocetes characterized by a heterodont dentition; as a result, the content of these two groups is in need 

of a detailed revision (Lockyer and Braulik, 2014; Marx et 

al., 2016). This task is far beyond the scope of this work, 

and we mostly deal here with squalodontid taxa that have 

been described on the basis of subcomplete cranial specimens 

in the genus Squalodon (see Kellogg, 1923a; Cabrera, 1926; 

Rothausen, 1968; Mchedlidze, 1976; Pilleri, 1985; Muizon, 

1991; Dooley, 2005).

Squalodon calvertensis Kellogg, 1923a

FIGURES 2.2, 2.3

Squalodon calvertensis – Squalodontidae

(Illustration by Brenna Litynski)
5 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
NUMBER 107 • 5 5

Holotype. USNM V 10484 (Figures 2.2, 2.3), a 

nearly complete skull, including most of the rostrum; the palatal region is incomplete, and the jugals are missing. The right 

periotic is preserved (Figure 2.3), but the tympanic bullae were 

lost. Seven cheek teeth and four incisor-like teeth were found associated with the skull (Figure 2.2). A mandible, two dorsal, and 

three lumbar vertebrae, six isolated epiphyses of vertebrae, 10 

ribs, and one ulna also belong to this specimen (Kellogg, 1923a). 

Bizygomatic width = 290 mm.

Type Locality. Western shore of Chesapeake Bay, 

approximately 3.2 km south of Chesapeake Beach, Calvert 

County, Maryland (Kellogg, 1923a).

Horizon and Age. The holotype was dug from the cliffs 

approximately 1.5 m above the beach. The specimen was apparently removed from SZ 6 of the Calvert Formation (Kellogg, 

1923a), late Early Miocene (Burdigalian).

Known Range. Within Maryland and Virginia, Squalodon calvertensis is known from the Popes Creek Sand to SZ 14, 

Fairhaven and Plum Point Members (Burdigalian to early 

Serravallian) of the Calvert Formation.

Referred Material. CMM-V-206, partial mandible, Popes Creek Sand unit, Fairhaven Member, Calvert Formation; CMM-V-208, 5 teeth, 5 cervicals, 6 thoracics, Calvert 

Formation; CMM-V-4644, partial mandible, Calvert Formation; 

USNM PAL 182944, skull element, partial tooth, SZ 4, Calvert 

Formation; USNM PAL 187315, partial skull, SZ 14, Calvert 

Formation; and USNM PAL 328343, skull lacking most of rostrum, 3 teeth in place, periotics (2), teeth (24), axis, cervicals (2), 

thoracics (2), ribs (4), humerus, Fairhaven Member, Calvert Formation. Whitmore and Kaltenbach (2008) list additional specimens attributed to Squalodon calvertensis collected from the 

Pungo River Formation in the Aurora Phosphate Mine (Aurora, 

North Carolina, approximately 35°20’N, 76°49’W).

Diagnosis of Species. Diagnostic characters of 

Squalodon calvertensis can be found in Kellogg (1923a), Dooley 

(2003, 2005), and Whitmore and Kaltenbach (2008).

FIGURE 2.2. (Opposite) Squalodon calvertensis. (A) USNM V 10484, holotype skull, dorsal view, anterior end of rostrum incomplete, mandible not shown. (B) Restoration of the skull in dorsal view (modified from Kellogg, 1928). The anterior part of the rostrum is based on other 

specimens of S. calvertensis in private collections where the rostrum is virtually complete. The facial region in the restoration is slightly shorter 

than in A because in the former, the skull is viewed from a more posterior vantage point. Consequently, in B, the supraoccipital gains a larger 

exposure than in A, and the exoccipitals are visible posterior to the squamosal fossae. (C–F) Teeth of S. calvertensis (USNM V 10484); lower? 

incisor, lower right anterior cheek tooth, upper left intermediate cheek tooth, and lower right posterior cheek tooth, respectively. Scale bar for 

C–F equals 10 mm.

FIGURE 2.3. Squalodon calvertensis. (A, B) Right periotic, USNM V 10484, holotype specimen, in dorsal and ventral views, respectively. Scale bar equals 10 mm.
5 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Remarks. The anteriormost teeth in the skull of 

S. calvertensis were strongly procumbent (Figure 2.2B). Dooley 

(2005) suggested that within the Squalodontidae, the anterior 

area of the rostrum (including the incisors) may have been subject to sexual dimorphism or ontogenetic variation. More recently, Fordyce et al. (2013) proposed that similar procumbent 

tusks in different odontocete clades (Waipatiidae, “Dalpiazinidae,” Squalodelphinidae, and Kentriodontidae) may have been 

used to probe sediment or for visual display. The rostrum of S. 

calvertensis was elongate and both absolutely and proportionately narrower compared to those of the other two squalodontid 

species known from the Chesapeake Group.

In recent phylogenetic analyses, S. calvertensis occurs either 

as an early branching member of a large clade, Platanistoidea (including the extant Platanista; e.g., Lambert et al., 2017c; Tanaka 

et al., 2017; Viglino et al., 2018a; Gaetán et al., 2019), or as one of 

the later diverging stem odontocetes (e.g., Lambert et al., 2017c; 

Vélez-Juarbe, 2017; Viglino et al., 2018a; Gaetán et al., 2019; Guo 

and Kohno, 2021). The addition of other squalodontid species in 

future phylogenetic analyses will most likely be useful for clarifying (1) the relationships of these late heterodont odontocetes and 

(2) the stem-crown transition for the whole suborder.

Squalodon whitmorei Dooley, 2005

FIGURE 2.4

Squalodon whitmorei – Squalodontidae

(Illustration by Brenna Litynski)

Holotype. USNM PAL 183023 (Figure 2.4), skull lacking the basicranium, part of the left frontal, parts of both maxillae, and the occipital condyles, with the squamosals detached; the 

specimen includes the proximal half of the left dentary; parts of 

10 teeth; portions of 29 vertebrae with the atlas, axis, 4 additional 

cervicals, 11 thoracics, 6 lumbars, and 6 caudals; the manubrium; 

and rib fragments, collected by John D. Kunlo in 1975 (Dooley, 

2005:2). Bizygomatic width estimated at 337 mm.

Type Locality. King George County, Virginia, at the 

north end of Mason Mill Pond, the head of Machodoc Creek, 18 

m above sea level, 2.6 km north of Edgehill (Dooley, 2005:2).

Horizon and Age. White to pinkish clayey sand, 

at least 2 m thick, suggesting that it derives from the Fairhaven 

Member of the Calvert Formation (“Popes Creek Sand” of Gibson, 1983), which correlates with the Burdigalian (late Early 

Miocene; Dooley, 2005:3).

Known Range. From the Fairhaven Member of the 

Calvert Formation in southern Maryland and northern Virginia 

and from the age-correlative Pungo River Formation in North 

Carolina (Dooley, 2005; Whitmore and Kaltenbach, 2008).

Referred Material. CMM-V-182, partial left mandible, Popes Creek Sand, Fairhaven Member, Calvert Formation; 

CMM-V-6459, section of mandible, Calvert Formation; and USNM 

PAL 424070, collected in King George County, Virginia. Additional 

specimens attributed to Squalodon whitmorei collected from the 

Pungo River Formation in the Aurora Phosphate Mine (Aurora, 

North Carolina) are listed by Whitmore and Kaltenbach (2008).

Diagnosis of Species. Diagnostic characters of 

Squalodon whitmorei can be found in Dooley (2005).

Remarks. Dooley (2005:11) provides a list of the morphological features in which Squalodon whitmorei differs from 

S. calvertensis. As in S. calvertensis, the anteriormost teeth in 

the skull of Squalodon whitmorei were strongly procumbent, as 

deduced from the orientation of anterior alveoli in the holotype 

and USNM PAL 424070 (Figure 2.4B). Apart from the sperm 

whales “Aulophyseter” mediatlanticus and Orycterocetus crocodilinus, Squalodon whitmorei was the largest toothed whale 

known within the Calvert Formation.

Squalodon murdochi sp. nov.

FIGURES 2.5, 2.6

Here we describe a new species of Squalodon on the basis of 

three specimens from the Calvert Formation.

Holotype. CMM-V-2287 (Figures 2.5, 2.6, Table 2.1), 

most of a broken/disarticulated skull (see details of preserved parts 

below), the symphyseal part of the mandible, and several detached 

teeth. An atlas, another partial vertebra, and several rib fragments 

were also recovered. The periotics and tympanic bullae were not 

recovered.

Type Locality. North of Willows Beach, Calvert 

Cliffs, Calvert County, Maryland. The skull of CMM-V-2287 

(Figures 2.5, 2.6) broke into many pieces when much of it fell naturally from high in the cliffs. What remained of the skull in the cliffs 

(most of the rostrum) was subsequently quarried in situ.

Horizon and Age. From SZ 10, Plum Point Member of the Calvert Formation. The Plum Point Member spans the 

Burdigalian–Langhian boundary of the Middle Miocene. Therefore, the skull is approximately 16 million years old.

Known Range. SZ 10–12, Plum Point Member 

(Langhian) of the Calvert Formation.

Etymology. The epithet murdochi was created in accordance with Article 31.1.2 of the ICZN (International Commission on Zoological Nomenclature, 1999) by adding an “i” to 

“Murdoch” to honor Paul R. Murdoch Jr., who found and reported the holotype skull to the CMM. Murdoch is an Irish/Scottish name derived from the Old Irish Gaelic words mur, meaning 

“sea,” and murchadh, meaning “sea warrior.”
NUMBER 107 • 5 7

FIGURE 2.4. Squalodon whitmorei. (A) USNM PAL 183023, holotype skull, dorsal view, anterior end of rostrum incomplete, 

mandible not shown. (B) Restoration of the skull in dorsal view. (C) Anterior cheek tooth of S. whitmorei (USNM PAL 183023). 

Scale bar for C equals 10 mm.
5 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.5. Squalodon murdochi sp. nov. (A) CMM-V-2287, holotype skull, dorsal view, lower jaw not shown. A 

portion of the left supraorbital process (white material) was scanned from that preserved on the right-hand side of the 

skull and mirror prototyped (by Research Casting International) to insert into the skull. (B) Restoration of the skull in 

dorsal view. (C) Posterior view of the supraoccipital.
NUMBER 107 • 5 9

FIGURE 2.6. Squalodon murdochi sp. nov. CMM-V-2287, holotype skull. (A–D) Anterior to posterior teeth, respectively, in lingual view. (E) Left maxilla in ventral view showing the small foramina and accompanying vascular 

furrows (at the tips of the six arrows). (F) Right maxilla in ventral view showing four (one partial and three complete) alveoli for posteriormost cheek teeth. Notice how these alveoli imbricate. (G) Right squamosal and adjacent 

bones in ventral view. Scale bar for A–D equals 10 mm.
6 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Referred Material. CMM-V-10280, one mandible with 17 teeth, a supraorbital, one vertebra, one partial rib 

and one tympanic bulla. SZ 10, Calvert Formation. CMM-V10317 disarticulated incomplete skull, atlas, and a few partial 

ribs. SZ 12, Calvert Formation.

Diagnosis of Species. With a condylobasal length of 

about 1040 mm, S. murdochi is intermediate in size between 

S. calvertensis and S. whitmorei. It differs from all other squalodontids (or taxa at least tentatively attributed to the family) 

for which the proximal region of the rostrum is well preserved 

(Eosqualodon langewieschei, Phoberodon arctirostris, S. antwerpiensis, S. barbarus, S. bariensis, S. bellunensis, S. calvertensis, S. peregrinus, S. whitmorei, and Squalodon sp. nov. from 

Belgium) in that the alveoli of the posterior upper cheek teeth 

are markedly crowded and consequently they imbricate (distal 

alveolus for a given tooth overlapping anteromedially with the 

mesial alveolus of the next, posterior tooth). It further differs 

from E. langewieschei, P. arctirostris, S. bariensis, S. bellunensis, 

S. calvertensis, S. peregrinus, and S. whitmorei in the presence 

of a distinct longitudinal ridge (Figure 2.5A) and groove on the 

dorsal surface of the frontal lateral to the part covered by the 

maxilla in the supraorbital region. Focusing on the other Squalodon species from the Calvert Formation, it further differs from 

S. calvertensis and S. whitmorei in the dorsal part of the occipital 

shield being excavated by two deep fossae separated by a distinct 

external sagittal crest (Figure 2.5C) and in the posteroventral 

margin of the paroccipital process being both proportionately 

and absolutely thicker (Figure 2.6G). It further differs from S. 

calvertensis in each frontal being anteroposteriorly longer than 

wide on the vertex; the palate being much more ventromedially 

projected; the absence of a hemispherical swelling of the posttympanic process; and the apex of the postglenoid process being 

mediolaterally wide and rounded in anterior view (vs. pointed in 

S. calvertensis), and from S. whitmorei in the upper tooth count 

being at least 18 for each side (16 in S. whitmorei) and the opening of the olfactory bulb lacking the development of a cylindrical 

tube.

Description. CMM-V-2287 consists of most of a 

broken/disarticulated skull (Figure 2.5). In addition to the larger 

identifiable pieces, the specimen also preserves many yet unidentified small bone fragments. The identifiable pieces include a 

nearly complete rostrum; most of the right supraorbital process; 

part of the left preorbital region; the vertex, including the frontals, although most of the premaxillae and the nasals were not 

recovered; the dorsomedial part of the supraoccipital; the left 

occipital condyle; and most of both squamosals and exoccipitals. The skull is thought to have come from a mature individual 

because the dental alveoli are well formed, the exoccipitals are 

firmly sutured to the squamosals, some broken roots of maxillary teeth are preserved in situ, and strong abrasion wear (both 

apical and on accessory denticles) is observed in the preserved 

teeth.

There is no osteological connection between the preserved 

rostral sections of the skull and the cerebral region (Figure 2.5A); 

consequently, the condylobasal length of the skull is an estimate. 

The right supraorbital section of the disarticulated skull was surface scanned and mirror image replicated to create most of the 

missing left supraorbital portion of the frontal (Figure 2.5A).

Premaxilla. The premaxillae appear to have been 

symmetrical along the rostrum. They did not abut dorsomedially; rather, they bordered a dorsally, widely open mesorostral 

canal that became increasingly deep posteriorly. The maximum 

width of the mesorostral canal is approximately 48 mm. The 

dorsal exposure of the premaxillae increases in width anteriorly, 

toward the incisor-bearing portion of the rostrum. Although only 

the two posterior premaxillary alveoli are well preserved on the 

TABLE 2.1. Measurements of the holotype skull of Squalodon murdochi sp. nov., CMM-V-2287, 

from the Middle Miocene, Shattuck-Zone 10, Plum Point Member, Calvert Formation, Calvert 

Cliffs, Maryland, USA.

Measurementa

Dimension (mm)

Condylobasal length of the skull as preserved 1,040

Length of rostrum (antorbital notch to anterior extremity) 690

Longitudinal distance between anterior of supraoccipital and posterior of bony nares 100

Width of skull across the postorbital processes 428

Maximum width of skull across zygomatic processes of squamosal 430

Orbital length 76

Width of skull across supraorbital processes 406

Width of rostrum at antorbital notch 200

Minimum distance between maxillae across the vertex 57

aAll measurements are estimated.
NUMBER 107 • 61

holotype, part of an additional anterior alveolus is preserved on 

the right premaxilla, yielding three procumbent upper incisors on 

each side. In a posterior direction, the premaxilla narrows posteriorly until about mid-rostrum length, only widening again from 

the level of the first dorsal infraorbital foramen. Better preserved 

on the right side, the premaxillary foramen enters the body of the 

bone approximately 35 mm in front of the anteriormost extremity of the frontal. A deep sulcus with an acute medial margin 

extends along the medial margin of the left premaxilla for at least 

138 mm anterior to the premaxillary foramen, probably corresponding to the anteromedial sulcus. The region of the premaxilla 

lateral to the sulcus becomes gradually more convex posteriorly. 

The premaxillary foramen is followed posteriorly by a short (25 

mm) longitudinal sulcus. The dorsal surface of the premaxilla is 

only transversely and longitudinally concave in the area posterior 

and posterolateral to the premaxillary foramen, making a small 

(about 30 mm long) premaxillary sac fossa. Posterior to the depression, the surface of the bone is flat to slightly transversely 

convex. On the vertex, an elongated empty space between the 

maxilla and the frontal was most likely originally occupied by the 

premaxilla (probably partly preserved on the right side), reaching 

a level not far from the nuchal crest. Ventrally, on the anterior 

part of the rostrum, the premaxillae are visible as a thin strip of 

bone between the maxillae.

Maxilla. Most of the robust rostral portion of the 

maxillae is preserved, with the dorsal exposure gradually widening posteriorly. The lateral surface of the right maxilla (and 

part of the premaxilla) is somewhat swollen at the level of the 

posterior margin of cheek tooth 1 (postcanine PC1), possibly 

corresponding to a healed trauma. Anterolateral to the left premaxillary foramen, a tiny dorsal infraorbital foramen (transverse 

diameter = 3 mm) is seen along the premaxilla-maxilla suture, 

followed anteriorly by a short sulcus. A second, larger foramen 

(14 mm long) is located posterolaterally, with two shallow posterior sulci, together with an even smaller foramen. Finally, a 

small circular foramen is observed on the medial wall of the antorbital notch. On the right side, a small dorsal infraorbital foramen, followed anteriorly by a sulcus, is about 40 mm anterior to 

the corresponding premaxillary foramen. Located more posterolaterally, a larger foramen with a diameter of 8 mm opens in a 

posterolateral direction, and three to four smaller foramina are 

visible more posteriorly and posterolaterally. Along the vertex, 

the better-preserved medial margin of the left maxilla remains 

low but is nearly vertical.

Posterior to the alveolus for the canine, located along the 

premaxilla-maxilla suture, alveoli for four single-rooted cheek 

teeth are preserved. A secondary incomplete septum between 

openings for anterior and posterior roots appears in right and 

left cheek tooth 5 (PC5), indicating the presence of fused doublerooted teeth; the intervening septum is more developed in PC6. 

On the basis of preserved segments of the right and left alveolar 

grooves, at least 14 cheek teeth were present in Squalodon murdochi, with 8 of these teeth being double rooted (at least with a 

slight constriction between anterior and posterior roots; Figure 

2.6). The minimum upper tooth count is thus 18, higher than the 

tooth count proposed for Eosqualodon langewieschei, Phoberodon arctirostris, S. bellunensis, and S. whitmorei (Cabrera, 

1926; Dooley, 2005; Viglino et al., 2018a; O. Lambert, personal 

observation). The transverse diameters of the openings of the 

conical tooth alveoli range from about 30 to 32 mm. Separation 

between individual tooth sockets gradually increases posteriorly, 

ranging from 6 mm between PC1 and PC2 to 14.5 mm between 

PC5 and PC6. More posteriorly, the gradually smaller alveoli 

become more crowded, with the posterior alveolus of PC12 and 

PC13 overlapping medially the anterior alveolus of the next 

tooth (PC13 and PC14, respectively; see Figure 2.6F, in which 

these teeth are seen to imbricate). A somewhat similar condition 

occurs in posterior lower cheek teeth of the early toothed mysticete Coronodon havensteini (Geisler et al., 2017) but is, to our 

knowledge, currently unknown in other squalodontids or any 

other heterodont odontocete (e.g., Moreno, 1892; Mchedlidze, 

1976; Fordyce, 1994; Gaetán et al., 2019; Viglino et al., 2018a; 

Boessenecker et al., 2020; Lambert, pers. obs.). A low depression 

on the interalveolar septum between PC4 and PC5 and on more 

posterior septa most likely indicates shallow embrasure pits. 

Medial to the last posterior cheek teeth, the maxilla is pierced 

by a number of small foramina (at least nine on the left side), 

followed anteriorly by narrow sulci, a condition suggesting developed vascularization of the palate in this area (Figure 2.6E).

At the level of the antorbital notch, there is a bold ventral 

ramus of the maxilla where contralateral sides appear to abut. 

The supraorbital portion of the maxilla was not preserved. Nevertheless, smooth bone lateral to the textured bone on the dorsal 

surface of the frontal indicates a wide exposure of the frontal lateral to the maxilla, intermediate between that of S. calvertensis

and S. whitmorei (compare Figures 2.2, 2.4, and 2.5).

Nasal. Our interpretation of the vertex suggests that 

the nasals are not preserved (Figure 2.5A). On the basis of the 

space available between the cribriform plate and the anterodorsal margin of the frontal on the vertex, each nasal was short and 

relatively narrow (as restored in Figure 2.5B). Reduced nasals 

appear to characterize most squalodontids.

Frontal. The anterolateral corner of the preorbital 

portion of the left frontal is 46 mm thick. Posterior to that point, 

the bone thins to 22 mm at the midpoint over the eye. Further 

posterior, the bone thickens once again where it forms the robust, short, and posteroventrally directed postorbital process. 

The dorsal surface of the frontal is marked by a conspicuous longitudinal ridge, extending lateral to the region originally covered 

by the maxilla (Figure 2.5A). Between this ridge and the lateral 

margin of the supraorbital process, the surface is markedly transversely concave.

The frontal–parietal complex on the vertex is greatly thickened in CMM-V-2287 (Godfrey, 2013). The midline length of 

the anteroposteriorly elongated frontals on the vertex is 78 mm, 

as measured from the cribriform plate back to the supraoccipital. Each frontal is longer than wide, and the lateral margins of 

frontals are roughly parallel and rectilinear. The dorsal surface is 
6 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

anteroposteriorly and transversely convex. The slightly sigmoidal interfrontal suture is shifted to the left (8–10 mm) compared 

to the external occipital crest.

Presphenoid. Much of the presphenoid is preserved 

in Squalodon murdochi. This element was illustrated by Godfrey 

(2013: figs. 2, 3; labeled in that publication as the mesethmoid; 

see Ichishima, 2016) in his description of the olfactory apparatus 

in CMM-V-2287. The presphenoid preserves the deep crescentic 

foramina and the nasal turbinates. At about the midpoint in the 

length of the crescentic foramina, the presphenoid thins to 15 

mm at its narrowest point.

Supraoccipital. The dorsal midline thickness of the 

supraoccipital (making the nuchal crest) is 12 mm. Lateral to 

that point, the bone thickens progressively but keeps a roughly 

transverse direction before turning abruptly posterolaterally 

and ventrally. Below this thickened nuchal crest are two bilateral pockets separated by a midline external occipital crest. This 

thickened band of bone presumably held the origin of the semispinalis muscle (Uhen, 2004).

Squamosal. Most of the right squamosal is preserved in CMM-V-2287 (Figures 2.5A, 2.6G). In dorsal view, 

a zigzagging suture marks the junction between the squamosal 

and parietal in the squamosal fossa. Posteriorly, the squamosal is strongly sutured to the thickened exoccipital (the greatest 

thickness of the exoccipital is 38 mm). Immediately anterior 

to the lateral exoccipital suture, the posterolateral face of the 

squamosal is excavated by three fossae, presumably for the 

sternocephalicus muscle, from a more anterodorsal fossa in line 

with the postglenoid process to a more posteroventral fossa 

along the lateral surface of the posttympanic process. Above 

this area, the supramastoid crest forms a sharp edge projecting posterolaterodorsally. Although the zygomatic process of 

the squamosal is incomplete, its dorsoventrally high (51 mm) 

and transversely thick (36 mm) anterior section indicates that 

it could have been considerably longer (although this is not indicated in the cranial restoration; Figure 2.5B). The postglenoid process is a remarkably anteroposteriorly thin blade for 

an otherwise very robust bone (Figure 2.6G). The glenoid fossa 

is broad and anteroventrally facing. Medial to the mandibular fossa, the tympanosquamosal recess is shallow, lacking any 

clear step. The recess extends slightly along the base of the 

postglenoid process and is somewhat deeper just anterior to 

the spiny process. The wide (6.5 mm at mid-length) external 

auditory meatus terminates medially with a short spiny process. The latter overhangs a small fossa (7 × 4.5 mm on the 

right side, smaller on the left side) probably homologous to the 

larger, deep subcircular fossa observed in several platanistoids 

(see Muizon, 1987, 1994; Viglino et al., 2018b). Anteromedial to this fossa, along the anterolateral margin of the ventral 

exposure of the parietal, two small foramina (only one larger 

foramen on the left side) pierce the floor of the periotic fossa, 

followed medially by a sulcus on the parietal. They may correspond to the foramen spinosum described in Waipatia (Fordyce, 

1994). The falciform process is broken at its transversely thick 

base, extending for about 40 mm anteroposteriorly. Posterior 

to the external auditory meatus, the posttympanic process is 

short (17 mm) and made of laminated bone.

The foramen ovale is not preserved, but the path for the mandibular nerve (cranial nerve V3) is distinct and directed anterolaterally (Figure 2.6G). Anteromedial to the path is a well-defined 

fossa for the pterygoid sinus in the alisphenoid. The paroccipital process of the exoccipital is transversely broad (Figure 2.6G) 

but only slightly protruding ventrally. Its ventral surface is deeply 

excavated, whereas its anteromedial surface is only slightly depressed, possibly for the posterior sinus. A shallow dorsal condyloid fossa is observed along the partly preserved left condyle.

Mandible. In total, 370 mm of the length of the symphyseal region of the left mandible are preserved. This mandible 

includes seven complete alveoli and a partly preserved alveolus 

at both the anterior and posterior ends. The floor of the anteriormost alveolus reveals holes for three posteroventrally directed 

roots, indicating the presence of at least two more anterior teeth. 

The total tooth count for this fragment is thus 11. The transverse 

diameter of alveoli ranges from 25 mm anteriorly to 21 mm posteriorly. A low secondary, incomplete septum indicating partial 

separation of anterior and posterior roots appears in alveolus 8, 

with the septum becoming more conspicuous in alveoli 9 and 

10. Embrasure pits appear beginning at alveolus 8. The first pit, 

which is observed anterolateral to alveolus 8, is shallow; pits become deeper more posteriorly and gradually shift to a more medial position. A minimum of five mental foramina are observed 

on the lateral surface of this mandibular symphysis.

Among detached teeth (Figure 2.6A–D), the anteriormost, 

procumbent teeth (Figure 2.5B) are subcylindrical but display 

clear mesial and distal carinae. Although serrations are inconspicuous, this could be related to wear, as more posterior singlerooted tooth carinae are serrated. Longitudinal ridges covering 

the enamel are low. Double-rooted teeth bear a narrow and 

thin ecto- and entocingulum, serrated carinae, and several (up 

to three) heavily worn, large accessory denticles along the distal 

carina. The maximum mesiodistal (anteroposterior) lengths for 

the three teeth included in Figure 2.6A–C are as follows: 19, 21, 

and 23 mm, respectively. The crown heights of these teeth are 

not included here because they are broken off, heavily worn, or 

a combination of both. Not enough teeth are preserved in place 

to know whether wear increased progressively posteriorly along 

the tooth row.

Remarks. Squalodon murdochi lived concurrently 

with S. calvertensis. The size differences between these two species may have contributed to interspecific niche partitioning.

Superfamily Physeteroidea Gray, 1868

There are only two named physeteroid species within the 

Miocene portion of the Chesapeake Group, the physeterids 

Orycterocetus crocodilinus Cope, 1868 and “Aulophyseter” mediatlanticus (Cope, 1895), although a few large teeth (see below) 

suggest the presence of at least one very large physeteroid.
NUMBER 107 • 6 3

Family Physeteridae Gray, 1821

Orycterocetus crocodilinus Cope, 1868

FIGURES 2.7, 2.8

Orycterocetus crocodilinus – Physeteridae

(Illustration by Brenna Litynski)

Holotype. ANSP 9126, one tooth.

Type Locality. Charles County, Maryland, not far 

from the Patuxent River, 3.2 km east of Hughesville.

Horizon and Age. No precise data are available for 

the holotype. However, Robert Weems (Weems and Edwards, 

2007) collected sediment from another cetacean discovered from 

the same locality (Balaenoptera? cephalus (Cope, 1867), ANSP 

12691) and had it successfully analyzed for dinoflagellates. The 

sample yielded a well-preserved dinoflagellate flora that characterizes the upper part of dinoflagellate zone DN5 of de Verteuil 

and Norris (1996), equivalent to SZ 14–16A of the Calvert Formation. Taking into account only the more diagnostic skull material (see below), specimens were found in SZ 9 and 11–14 of 

the Calvert Formation. The species thus ranges from the latest 

Early Miocene to the Middle Miocene (late Burdigalian, Langhian to early Serravallian).

Known Range. Within the Chesapeake Group, 

Orycterocetus crocodilinus is known with certainty from SZ 

9–14, Plum Point Member (late Burdigalian to early Serravallian) of the Calvert Formation. Isolated teeth similar to Orycterocetus crocodilinus are known from the lower Calvert Popes 

Creek Sand (Gary Grimsley, personal communication, 28 March 

2022). On the basis of cranial material, Orycterocetus crocodilinus is also recorded from the Middle Miocene of Belgium (Lambert, 2008) and, more tentatively, from the Miocene of France 

(Ginsburg and Janvier, 1971).

Referred Material. USNM V 10860, right periotic, Calvert Formation; USNM V 11234, right periotic, Calvert 

Formation; USNM V 14729, skull, SZ 11?, Calvert Formation; 

USNM V 14730, skull, SZ 12, Calvert Formation; USNM V 

22926 (Figure 2.7B,C), skull (bizygomatic width = 485 mm) 

with teeth and part of an associated mandible, SZ 13, Calvert 

Formation; USNM V 22930, skull, SZ 12, Calvert Formation; 

USNM V 22931, skull, SZ 9, Calvert Formation; USNM V 

22953, right periotic and tympanic bulla (Figure 2.8), SZ 14, 

Calvert Formation; USNM V 22967, rostral fragment, SZ 12, 

Calvert Formation; USNM PAL 183078, partial mandible and 

teeth (Figure 2.7D,E), SZ 12, Calvert Formation; and USNM 

PAL 336585, both mandibles with most upper and lower teeth, 

periotic and tympanic bulla, and some vertebrae and ribs, SZ 

12, Calvert Formation.

Diagnosis of Species. Diagnostic characters of 

Orycterocetus crocodilinus can be found in Kellogg (1965). Note 

that Kellogg actually provided a diagnosis for the genus Orycterocetus, not for the species O. crocodilinus. However, because 

O. quadratidens (the type species for the genus) is known from 

only two teeth, two partial mandibular rami, and a rib from the 

Neogene of Virginia (Leidy, 1853), we consider Orycterocetus 

quadratidens indeterminate and consequently apply the diagnosis to the species O. crocodilinus. Consequently, Orycterocetus 

quadratidens is designated as a nomen dubium.

Remarks. Considering the low number of diagnostic 

characters and the intraspecific variability observed for physeteroid teeth (e.g., Bianucci and Landini, 2006; Whitmore and 

Kaltenbach, 2008), the holotype teeth of Orycterocetus quadratidens and O. crocodilinus most likely do not bear enough 

information to comprise the diagnosis of their respective species. In reference to the pieces of the type specimen of the genus 

and species, O. quadratidens, Kellogg (1925c:10) makes the 

following observation: “These specimens should be in the 

Academy of Natural Sciences of Philadelphia, but so far as I 

am aware they have not been seen by anyone since 1869 when 

Leidy again mentioned and described them.” The third strike 

against O. quadratidens is that there is no locality information (geographic or stratigraphic) as to where in Virginia the 

type specimen was collected. These three liabilities relative to 

O. quadratidens provide the basis for designating this species 

as a nomen dubium.

There is a partial skull, USNM PAL 336585, attributed to 

O. crocodilinus that preserves teeth that in isolation would be 

identified as those of O. quadratidens and other teeth in the same 

specimen that would be identified as those of O. crocodilinus

(Bohaska, 1998). This would suggest that O. quadratidens and 

O. crocodilinus are synonymous, with O. quadratidens having 

priority. However, we do not advocate taking this route because 

of the high degree of intraspecific variability observed for physeteroid teeth (e.g., Bianucci and Landini, 2006; Whitmore and 

Kaltenbach, 2008).

As for the taxonomic validity of O. crocodilinus, since 

Kellogg’s (1965) attribution of well-preserved skulls to the species, O. crocodilinus has long been considered a valid taxon. 
6 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.7. Orycterocetus crocodilinus. (A) Restoration of the skull in dorsal view. From Kellogg (1965). (B, C) USNM V 

22926, nearly complete skull in dorsal and oblique left anterodorsolateral views, respectively. (D, E) USNM PAL 183078, 

teeth. Scale bar for D and E equals 10 mm.
NUMBER 107 • 6 5

FIGURE 2.8. Orycterocetus crocodilinus. (A, B) USNM V 22953, right periotic in ventral and dorsal views, respectively. (C, D) 

USNM V 22953, right tympanic bulla in ventral and dorsal views, respectively. A and B whitened with sublimed ammonium 

chloride to improve contrast. Scale bars equal 10 mm. The large accessory ossicle of the tympanic bulla remains attached to the 

anterior process of the periotic. When it is detached, the fovea epitubaria is visible. This feature is not restricted to physeterids but 

is particularly noticeable in this clade of odontocetes (Bohaska, personal communication, 17 February 2019).
6 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

We therefore recommend keeping this genus and species name 

for all the cranial specimens from the Calvert Formation referred 

by Kellogg to O. crocodilinus. Attributions of other isolated 

teeth (for example, USNM V 1158 from the Choptank Formation) should be dealt with carefully, considering the Miocene diversity of physeteroids (not only physeterids but also kogiids) in 

the North Atlantic realm (Lambert, 2008; Whitmore and Kaltenbach, 2008). A detailed review would also be needed to evaluate 

whether other fragmentary remains (e.g., ear bones) can safely be 

referred to the same species.

USNM V 22926 is from a larger individual (USNM PAL 

336585 is from an even larger individual; Bohaska, personal 

commmunication, 1 March 2022), displaying marked differences in the proportions of the supracranial basin from smaller 

specimens (e.g., USNM V 14730). Could such a degree of intraspecific variation be explained by sexual dimorphism within 

O. crocodilinus? At present, there is no compelling evidence 

for such a hypothesis; a larger sample of well-preserved crania 

would be needed to test it, helping to decipher when and how 

increased sexual dimorphism (as observed in the extant Physeter macrocephalus) evolved (Cranford, 1999). In addition, 

more complete specimens of O. crocodilinus may provide valuable clues on the timing of the marked reduction of the upper 

dentition that occurred among physeterids, ultimately leading 

to the nonfunctional upper teeth of P. macrocephalus, which 

often remain hidden in the gum (Boschma, 1938). In USNM 

PAL 336585, almost all the teeth are present, and they show no 

marked difference in size (Bohaska, perssonal communication, 

1 March 2022).

Orycterocetus crocodilinus’s phylogenetic relationships 

have been tested in a number of analyses, and this species has 

been recovered as a stem physeteroid (e.g., Velez-Juarbe et al., 

2015), as an early branching physeterid (e.g., Lambert et al., 

2017a; Collareta et al., 2019; Paolucci et al., 2020a; Alfsen et 

al., 2021), and in an unresolved polytomy with kogiids and physeterids (e.g., Benites-Palomino et al., 2020b).

With such a sample of well-preserved skulls, including associated ear bones, Orycterocetus crocodilinus is probably the 

best-known extinct physeteroid. The largest skull of O. crocodilinus is estimated to have been 950 mm in length (Kellogg, 1965). 

We estimate that the total body length of O. crododilinus was 

between 3 and 4 m. The relatively slender teeth and lightly built 

rostrum in O. crocodilinus indicate that this sperm whale was 

not macroraptorial like some of its relatives from the Miocene 

of California, Italy, Japan, and Peru (Acrophyseter spp., Albicetus oxymycterus, Brygmophyseter shigensis, Livyatan melvillei, 

and Zygophyseter varolai; Lambert et al., 2017a, and references 

therein). Whereas the presence of upper alveoli on the narrow 

and elongated rostrum suggests that O. crocodilinus could seize 

prey using its jaws, the loss of dental enamel is a derived condition shared, among others, with the extant, suction-feeding physeteroids Kogia and Physeter (Velez-Juarbe et al., 2015; Lambert 

et al., 2017a).

“Aulophyseter” mediatlanticus (Cope, 1895)

FIGURE 2.9

“Aulophyseter” mediatlanticus – Physeteridae

(Illustration by Brenna Litynski)

Holotype. USNM V 9463 (Figure 2.9), a partial skull 

including the proximal part of the rostrum and the right supraorbital region. See Cope (1895), Case (1904), and Kellogg (1925c) 

for a description, measurements, and figures of this specimen. 

Type Locality. Drum Point (southern end of Calvert 

Cliffs), Calvert County, Maryland.

Horizon and Age. Little Cove Point Member of the 

St. Marys Formation, early Late Miocene (Tortonian).

Known Range. SZ 22–23, Little Cove Point Member (Tortonian) of the St. Marys Formation.

Referred Material. USNM V 10594, partial skull 

(Cope, 1895), St. Marys Formation.

Diagnosis of Species. Diagnostic characters of 

“Aulophyseter” mediatlanticus can be found in Kellogg (1925) 

and Kazár (2002).

Remarks. Although beyond the scope of this work, 

a reassessment of this species in light of more recent finds, as 

well as phylogenetic analyses and a systematic review of the 

genera Aulophyseter and Orycterocetus, would likely shed light 

on the affinities of this poorly known taxon. The attribution to 

the genus Aulophyseter (Kazár, 2002), first recorded from the 

Middle Miocene of California (Aulophyseter morricei; Kellogg, 

1927b), should be considered questionable at best, given the differences from the type species observed in the facial region (lateral extent of the supracranial basin, number, size, and position 

of dorsal infraorbital foramina). Better-preserved material would 

allow for the testing of this hypothesis (and others, as the species 

was referred to the genera Diaphorocetus and Orycterocetus before its present attribution [see Kellogg, 1925c]; it further shares 

some similarities with Physeterula dubusi from the Miocene of 

the North Sea) in a phylogenetic context. Most recently, Paolucci 

et al. (2020b) noted that there was not enough evidence to refer 

USNM V 9463 to the genus Aulophyseter and confirmed that a 

detailed review was needed to determine its taxonomic status.
NUMBER 107 • 6 7

FIGURE 2.9. “Aulophyseter” mediatlanticus. (A–C) Holotype skull, USNM V 9463. (A) Interpretative drawing of 

photo (B), including one possible outline of the restored skull in dorsal view. (C) Right anterodorsolateral view of the 

partial skull.
6 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

From the portion of the skull that is preserved, it is obvious 

that “Aulophyseter” mediatlanticus possessed the largest skull 

of any of the named odontocetes from the Calvert, Choptank, 

and St. Marys Formations, the postorbital width of the skull 

being estimated at 800 mm (Cope, 1895) and the width at rostrum base at 660 mm. The presence of large (transverse diameter 

ranges between 25 and 28 mm), but shallow, upper alveoli (nine 

preserved on the right side and eight on the left side) indicates 

that this animal was able to catch large prey with its teeth, a 

condition less derived than in the extant physeteroids Kogia and 

Physeter. However, the posterior end of the alveolar groove is 

distant (about 385 mm) from the antorbital notch, suggesting 

some degree of reduction of the upper dentition compared to 

that of stem physeteroids and other toothed cetaceans (Lambert 

et al., 2017a).

Physeteroidea indet.

FIGURE 2.10

Of all the Chesapeake Group physeteroid teeth in the collections of the USNM and CMM, the specimen shown in Figure 2.10 is so relatively large that it, in our estimation, deserves 

a mention in this review chapter. What it illustrates, especially 

for the benefit of the large amateur community that will reference this work, is that there are more odontocete species to be 

described following the discovery of additional cranial material 

from the Calvert Cliffs area.

Locality. Chesapeake Ranch Estates Beach, Calvert 

Cliffs, Maryland.

Horizon and Age. Choptank Formation or St. 

Marys Formation. Considering the color and aspect of the bone, 

the latter is more likely. Late Middle to early Late Miocene (Serravallian to Tortonian).

Referred Material. USNM PAL 167608, a large 

tooth (Figure 2.10) lacking the crown and part of the cementum 

layer covering the root. 

Description. Most likely lacking only a few centimeters apically, this large, robust tooth is 251 mm long, with a 

maximum diameter of the root of 79.5 mm. The open pulp cavity is oval in cross section, with a maximum diameter of 31 mm. 

At mid-length of the root, the cementum layer is 12 mm thick. 

The root is moderately curved, and as for the pulp cavity, its 

cross section is distinctly flattened (maximum diameter perpendicular to the plane of curvature).

Remarks. This tooth is probably much too large to 

have come from either of the two physeteroids recorded from 

Calvert Cliffs, that is, “Aulophyseter” mediatlanticus and Orycterocetus crocodilinus (transverse diameter of upper alveoli less 

than 45 mm in the former and less than 15 mm in the latter), 

unless “A.” mediatlanticus is highly sexually dimorphic and this 

is a male lower tooth. Although lacking the crown, it shares similarities with teeth from the Miocene of the North Sea referred to 

the large, presumably stem physeteroid Scaldicetus caretti (du 

Bus, 1867; Abel, 1905). Among the 45 teeth of the lectotype 

(i.e., a specimen chosen as the type of a species if the author 

of the name failed to designate a type) of that species, IRSNB 

M.512, found in Antwerp, the largest display similar outlines 

and proportions, with the maximum diameter of the root (73 

mm) only slightly smaller than in USNM PAL 167608 (Lambert 

and Bianucci, 2019). Because the type material consists of only 

teeth with poor diagnostic value, Scaldicetus caretti has been restricted to the lectotype, whereas other specimens previously referred to the species have been identified as Physeteroidea indet. 

(Bianucci and Landini, 2006). Furthermore, as mentioned below, 

at least two physeteroid genera known from skulls have Scaldicetus-like teeth. Knowing that tooth morphology alone does 

not confirm taxonomic identity within some physeteroids, we 

will refrain from assigning this tooth taxonomically, pending the 

discovery of diagnostic cranial remains. Still, this tooth indicates 

the presence of a very large sperm whale in the northwestern 

Atlantic during the late Middle to early Late Miocene; the only 

other Miocene physeteroids with teeth larger than USNM PAL 

167608 are the macroraptorial stem physeteroids Livyatan melvillei, early Late Miocene of Peru (Lambert et al., 2010a), and 

Albicetus oxymycterus, Middle Miocene of California (based on 

alveolar diameters; Boersma and Pyenson, 2015). Keep in mind 

that physeteroid teeth increase in diameter throughout life, so 

tooth diameter and alveolar size should be used with caution 

(Gilbert et al., 2018).

Family Ziphiidae (Gray, 1850) Gray, 1865

There are 19–23 species of living beaked whales characterized by a long and slender beak-like rostrum, bold elevation 

of the narial region, pronounced cranial asymmetry, enlarged 

pterygoid sinuses, and a greatly reduced dentition in all genera 

except Tasmacetus (Hooker, 2001; Fordyce, 2009a; Mead, 2009; 

McLeod, 2018). All living ziphiids inhabit the open ocean and 

suction feed at depth on squid and fish (Mead, 2009; Marx et 

al., 2016). The geologically oldest named member of the family 

originates from the Antwerpen Sands Member of the Berchem 

Formation, Middle Miocene of the North Sea (Lambert and 

Louwye, 2006), although more fragmentary remains and a controversial specimen have been described from the Early Miocene 

(Muizon, 1991; Bianucci et al., 2005). The quintessential ziphiid 

morphology exhibited by some of the oldest known constituents 

indicates the existence of even older unknown or unrecognized 

stem ziphiids. Beginning in the Miocene, ziphiids became global 

in their distribution (Mead, 1975; Muizon, 1983; Tazaki et al., 
NUMBER 107 • 6 9

1987; Bianucci et al., 1992, 2007, 2016c; Bianucci, 1997; Lambert, 2005b; Lambert and Louwye, 2006; Lambert et al., 2009, 

2018b; Buono and Cozzuol, 2013).

There are only two published reports of fossil ziphiids from 

the Miocene portion of the Chesapeake Group in Maryland: a 

partial rostrum from the St. Marys Formation referred to cf. 

Messapicetus sp. (Fuller and Godfrey, 2007) and a specimen represented by USNM PAL 476359 and CMM-V-4267 (both casts 

of the original specimen; the original specimen is now unavailable, kept in a private collection, and its whereabouts are now 

unknown) probably from the Calvert Formation (Lambert et 

al., 2010b). Gottfried et al. (1994) reported on three ziphiids 

probably from the Choptank Formation that were later shown 

to be pathological (forms of periostitis; Gerholdt and Godfrey, 

2010). Although in error, True (1908a:456) thought that a fragment of a skull from Schizodelphis crassangulum (the holotype 

specimen of Priscodelphinus crassangulum, which True referred 

to Schizodelphis, but with a different concept of that genus than 

used today) was the side of the basisphenoid of a species of the 

ziphiid Mesoplodon (Bohaska, personal communication, 17 February 2019).

Genus Messapicetus Bianucci, Landini, and Varola, 1992

Type Species. Messapicetus longirostris Bianucci, 

Landini, and Varola, 1992, from Southern Italy (see also Bianucci et al., 2016a).

cf. Messapicetus sp.

FIGURE 2.11C–E

cf. Messapicetus sp. – Ziphiidae

(Illustration by Tim Scheirer)

Locality. The partial rostrum, CMM-V-3138 (Figure 

2.11C–E), was collected from the beach near the southern end of 

Calvert Cliffs between Little Cove Point and Drum Point, Calvert 

County, Maryland. 

FIGURE 2.10. USNM PAL 167608, a large Physeteroidea indet. tooth lacking the crown and part of the cementum layer covering the root.
7 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.11. Ziphiidae. (A, B) Ziphiidae indet., partial skull that includes the rostrum and prenarial 

region in dorsal and ventral views, respectively. Drawings are based on the original specimen, kept in 

a private collection, whereas casts, USNM PAL 476359 and CMM-V-4267, are curated at the USNM 

and CMM, respectively. Reformatted from Lambert et al. (2010b). (C–E) CMM-V-3138 cf. Messapicetus sp., which consists of a partial rostrum, in dorsal, left lateral, and ventral views, respectively. 

Reformatted from Fuller and Godfrey (2007).
NUMBER 107 • 71

Horizon and Age. Little Cove Point Member of the 

St. Marys Formation (SZ 22–23), Tortonian.

Known Range. SZ 22–23, Little Cove Point Member 

(Tortonian) of the St. Marys Formation.

Referred Material. CMM-V-3138 (Figure 2.11

C–E), a partial rostrum.

Diagnosis. Diagnostic characters of Messapicetus can 

be found in Bianucci et al. (1992, 2010, 2016a).

Description. CMM-V-3138, cf. Messapicetus sp., 

which consists of a partial rostrum, was described in detail by 

Fuller and Godfrey (2007). Distinct tooth alveoli are present in 

the maxillae, but no teeth were found in association with the 

rostrum. The alveoli in CMM-V-3138 are well developed and 

should not be considered rudimentary (Figure 2.11D). Although 

the sockets have been abraded, they give no indication of the former presence of double-rooted teeth. Many of the empty sockets 

are roughly square in outline like those of Messapicetus longirostris (Bianucci et al., 1994: fig. 6a1

) and Ninoziphius platyrostris

(Muizon, 1984: figs. 76–78) and suggest the presence of similarly 

shaped teeth in CMM-V-3138. As in M. longirostris (Bianucci 

et al., 1994), the length and height (labial-lingual dimension) of 

the alveoli range from 10 to 13 mm. There is a change in the 

orientation of the alveoli along the rostrum and, presumably, a 

concomitant change in the orientation of the teeth. Anteriorly, 

the orientation of the alveoli suggests that teeth pointed ventrolaterally. Moving to the posterior end of the rostral segment, a 

gradual change in the orientation of the alveoli suggests that the 

teeth projected laterally. Notice also that in CMM-V-3138, cf. 

Messapicetus sp., thickened premaxillae enclose the mesorostral 

canal, a condition shared with a number of stem ziphiids (Bianucci et al., 2016a).

Remarks. During the Middle to Late Miocene, there 

was open communication between the Atlantic and Pacific 

Oceans (i.e., an open Central American Seaway; Jacobs et al., 

2004; Montes et al., 2015). Not unlike extant ziphiid genera, 

which are pelagic and generally have a wide geographical distribution (McLeod et al., 2006), in addition to the Italian form 

(M. longirostris), Messapicetus is now also known to have lived 

in the Pacific Ocean (Messapicetus gregarius; Bianucci et al., 

2010) during the early Late Miocene (Pisco Formation of Peru; 

Bianucci et al., 2016a). This closely related form is thought to 

represent a contemporaneous sister species of M. longirostris

with an antitropical distribution (Bianucci et al., 2016a).

Morphological similarities further suggest that the two species of Messapicetus may have occupied roughly identical ecological and trophic niches (Bianucci et al., 2016a). Lambert et 

al. (2015a) and Bianucci et al. (2016c) proposed that unlike 

extant ziphiids that specialize in suction feeding, stem ziphiids 

within the genus Messapicetus were raptorial piscivores that 

fed mainly on schools of clupeid fish in neritic and/or epipelagic 

environments.

Ziphiidae indet.

FIGURE 2.11A,B

Ziphiidae indet.

(Illustration by Tim Scheirer)

Locality. The skull was dredged from the bottom of 

the Chesapeake Bay, 180 m directly offshore from the Calvert 

Cliffs Nuclear Power Plant (now owned by Constellation Energy), Calvert Cliffs, Maryland.

Horizon and Age. Dinoflagellates in associated 

sediment suggest an origin in SZ 12–15 of the Calvert Formation, Middle Miocene (L. Edwards, personal communication, 

2009; Lambert et al., 2010b).

Known Range. SZ 12–15, Plum Point Member 

(late Langhian to early Serravallian) of the Calvert Formation. 

Clearly, one specimen could not originate from four SZ. However, at this time, this range is given on the basis of the diversity 

of dinoflagellates associated with the partial skull, which do not 

permit a more precise stratigraphic designation.

Referred Material. USNM PAL 476359 and 

CMM-V-4267 (both casts of the original specimen), partial 

skull (rostrum and prenarial region). Note that Figure 2.11A,B 

is based on the original specimen, which is currently in a private 

collection (present location unknown).

Ziphiid features of USNM PAL 476359 (observed in at least 

some of the known ziphiids) include strongly asymmetric premaxillae in the facial region, highly reduced maxillary alveolar groove, 

and pachyosteosclerotic bones on the dorsal surface of the skull. 

Whereas the sutural contact between the thick premaxillae dorsal 

to the mesorostral canal is present only in members of the stem 

ziphiid Messapicetus clade (Bianucci et al., 2016c), the absence 

of a conspicuous prenarial basin in this specimen differs markedly from the condition in Aporotus, Beneziphius, Messapicetus, 

and Ziphirostrum. Furthermore, the medial separation of the premaxillary sac fossae is absent in Choneziphius. The highly asymmetrical premaxillary sac fossae and the development of a thick 

anterior margin on the right fossa are reminiscent of the condition in Caviziphius altirostris, Eboroziphius coelops, the fragmentarily known Pelycorhamphus pertortus, and Tusciziphius crispus

(see Post et al., 2008). However, these taxa display differences: 

the rostrum of Caviziphius is much deeper, the premaxillae of 

Caviziphius and Eboroziphius are hollowed by a pair of wide longitudinal grooves along the rostrum, and the right premaxillary 

sac fossa of Pelycorhamphus is much more excavated.
7 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Although Tusciziphius additionally shares with USNM PAL 

476359 the wide subhorizontal maxillae on the dorsal surface of 

the rostrum and a transverse sulcus crossing the right premaxillary sac fossa, the premaxillae of USNM PAL 476359 are less 

elevated, not as completely fused, and much wider at the base of 

the rostrum. Furthermore, Tusciziphius lacks any crest along the 

lateral margin of the rostrum base; it is smaller, and its rostrum 

is less dorsoventrally flattened. Even if some of the differences 

mentioned here could be explained by ontogeny or sexual dimorphism, this specimen most likely belongs to a new taxon related 

to Tusciziphius crispus, from the Late Miocene to Early Pliocene 

of Italy and the East Coast of the United States. This specimen 

represents the first record of a ziphiid in the Middle Miocene 

Calvert Formation.

Remarks. If, like their living counterparts, Miocene 

ziphiids frequented deep marine habitats (but see Lambert et al., 

2015a), then the scarcity of ziphiid remains within the Chesapeake Group is potentially a paleoenvironmental sampling artifact indicative of the relatively shallow water depth within the 

Miocene Salisbury Embayment (Gottfried et al., 1994), rather 

than their absolute rarity within the Miocene western North 

Atlantic. However, this scarcity contrasts markedly with the 

higher number of ziphiid specimens and associated higher diversity observed in the relatively shallow Middle Miocene to Early 

Pliocene marine deposits of the southern margin of the North 

Sea Basin (Lambert, 2005b; Lambert and Louwye, 2006); one 

needs to keep in mind that a majority of the Miocene Chesapeake Group odontocetes are known from only a few specimens 

or single partial skulls. Consequently, the sample size might just 

not be large enough to begin to draw these kinds of conclusions.

Unranked Clade Platanidelphidi Bianucci, Muizon, 

Urbina, and Lambert 2020

Family Squalodelphinidae (Dal Piaz, 1916) Rice, 1998

Squalodelphinids constitute an extinct lineage of late Oligocene through Miocene odontocetes (Barnes et al., 2010; 

Marx et al., 2016). These small to medium-sized odontocetes 

are known from both hemispheres (Mediterranean, North and 

South Atlantic, North and southeastern Pacific; Moreno, 1892; 

Dal Piaz, 1916; Kellogg, 1957; Muizon, 1987; Lambert et al., 

2014; Bianucci et al., 2015, 2018, 2020; Nelson and Uhen, 

2018; Kimura, 2019). To date, species assigned to this family 

exhibit skulls with proportions similar to those of living delphinids (e.g., Bianucci et al., 2018). Squalodelphinid skulls display 

a robust rostrum of moderate length with single-rooted teeth at 

least occasionally showing slight but obvious heterodonty (accessory denticles on the crown of posterior teeth) and thickened 

supraorbital processes without the facial crests (elevated bony 

knobs above the orbits) so often seen and usually more highly 

developed in closely related platanistids (Boersma et al., 2017; 

but see Bianucci et al., 2020, for an alternative hypothesis). It is 

worth noting that the Squalodelphinidae appear as a monophyletic group in only some recent phylogenies (e.g., Lambert et al., 

2014; Boersma et al., 2017; Bianucci et al., 2018, 2020 versus 

Tanaka et al., 2017; Viglino et al., 2018b).

Two squalodelphinids are currently known from the Chesapeake Group: Phocageneus venustus (Leidy, 1869; Kellogg, 

1957) and fragmentary material previously tentatively referred 

to Notocetus sp. (Kellogg, 1957; Muizon, 1987).

Phocageneus venustus Leidy, 1869

FIGURES 2.12, 2.13

Phocageneus venustus Leidy, 1869 was established on the 

basis of the description of a single tooth (ANSP 11227), one 

that Louis Agassiz incidentally had earlier identified as belonging to the fossil seal Phocodon (Kellogg, 1957; Whitmore and 

Kaltenbach, 2008). The tooth derives from diatomaceous deposits of the Calvert Formation near Richmond, Henrico County, 

Virginia, although Whitmore and Kaltenbach (2008:190) noted 

that the exact location and source rock are not known. Kellogg 

(1957) assigned one other specimen, USNM V 21039, consisting 

of an incomplete mandible, 16 detached teeth, both tympanic 

bullae and periotics, right and left mallei, right incus, left stapes, 

and numerous postcranial elements to this species. Whitmore 

and Kaltenbach (2008) observed that none of the teeth in this 

specimen ideally matched the type and therefore revised the identity of USNM V 21039 as aff. Phocageneus venustus and limited 

the species Phocageneus venustus to include only the holotype 

tooth.

However, because similar tooth morphologies can occur in 

disparate odontocetes (a single tooth is often not sufficient to 

distinguish it from close relatives), Kellogg would have been justified to designate Phocageneus venustus Leidy, 1869 as a nomen 

dubium and use the assigned specimen, USNM V 21039, as the 

type for a newly named odontocete species. Given that Kellogg 

did not do that and following Muizon (1987) and Lambert et al. 

(2014), we too will retain the status quo in an effort to minimize 

taxonomic entanglement, recognizing that in the future it may 

be possible to show that the type tooth ANSP 11227 and the 

referred specimen USNM V 21039 are not conspecific.

Kellogg’s (1957) description of USNM V 21039 (including postcranial elements) is sufficiently detailed that it will not 

be repeated here. Unfortunately, other than the aforementioned 

bones associated with the otic region and the mandible, no other 

parts of the skull are known.

Holotype. ANSP 11227, one tooth.

Type Locality. Richmond, Henrico County, Virginia.

Horizon and Age. “Presumably from the diatomaceous deposits, Calvert Formation, upper Miocene” (Kellogg, 

1957:282). The Calvert Formation overlaps portions of the Early 

and Middle Miocene, but not the Late Miocene, so Kellogg’s 

referral of the diatomaceous deposits to the Upper Miocene is puzzling. The highly diatomaceous deposits in Richmond, Virginia, 
NUMBER 107 • 7 3

correspond to the Choptank Formation, are correlative with SZ 

19, and are Middle Miocene in age (Andrews, 1986). Whitmore 

and Kaltenbach (2008:190) presume that the specimen came from 

the Calvert Formation (Leidy, 1869:426) but go on to state that 

“the exact locality and source rock are not known.”

Known Range. Fairhaven Member (Burdigalian) of the 

Calvert Formation.

Referred Material. USNM V 21039, mandibles, 

lacking anterior portion of symphysis (Figure 2.12A,B); right 

and left periotic (Figure 2.13A,B); right and left tympanic bulla 

(Figure 2.13C); right and left malleus; right incus; left stapes; 16 

detached teeth (a few of which are shown in Figure 2.12D,E); 

atlas and 3 cervical vertebrae; 10 thoracic vertebrae; 2 lumbar 

vertebrae; 4 caudal vertebrae; 2 chevrons; 1 sternal segment; and 

portions of 5 ribs. Collected 0.4 km south of wharf at Fairhaven, 

Fairhaven Cliffs, Anne Arundel County, Maryland, about 2.4 

m above base of cliff; SZ 3B of the Fairhaven Member, Calvert 

Formation, Early Miocene.

Additional specimens attributed to aff. Phocageneus venustus and Phocageneus cf. P. venustus and collected from the 

Pungo River Formation in the Aurora Phosphate Mine (Aurora, 

North Carolina) are listed by Whitmore and Kaltenbach (2008) 

(see Remarks below).

Diagnosis of Species. Diagnostic characters of 

Phocageneus venustus can be found in Kellogg (1957).

Remarks. Whitmore and Kaltenbach (2008) identified 

USNM PAL 475596 as a badly crushed skull of Phocageneus, 

cf. P. venustus, from the Pungo River Formation in the Aurora 

Phosphate Mine (Aurora, North Carolina). The only parts overlapping with the referred specimen, USNM V 21039, are a detached tooth and a fragment of a periotic. Lambert et al. (2014) 

and Boersma et al. (2017) subsequently identified it as squalodelphinid indeterminate because of the difficulty of comparing it 

with Calvert Formation specimens.

The discovery of a complete skull of P. venustus from along 

Calvert Cliffs would show how this squalodelphinid compares 

to other members of the family. Skulls of Phocageneus are most 

likely to occur low in the Calvert Formation, that is, along the 

Potomac River cliffs near Popes Creek, Maryland, and Fairhaven, 

Maryland (the northernmost exposures of the Calvert Cliffs).

Squalodelphinidae indet.

FIGURE 2.14

Localities. USNM PAL 206286 was found in Prince 

George’s County, Maryland. USNM PAL 310632 was found in 

the cliffs down river from Popes Creek, Charles County, Maryland, approximately 2 m above beach level.

Horizon and Age. USNM PAL 206286 originated 

from an unknown level of the Calvert Formation. USNM PAL 

310632 was collected from the Popes Creek Sand, Calvert Formation, late Aquitanian.

Known Range. Popes Creek Sand unit of the Calvert 

Formation.

Referred Material. USNM PAL 206286, right 

periotic (Figure 2.14D,E), also illustrated by Muizon (1987), 

and partial tympanic bulla. USNM PAL 310632 (Figure 2.14A–

C), a partial skull including part of the proximal region of the 

rostrum, two supraorbital processes, and the vertex. Postorbital 

width equals 207 mm.

Description. With a width at rostrum base of 

117 mm, a postorbital width of 207 mm, and a width of the 

bony nares estimated at 40 mm, USNM PAL 310632 is much 

smaller than the holotype of Macrosqualodelphis ukupachai; 

smaller than specimens of Furcacetus flexirostrum, Notocetus 

vanbenedeni, and Squalodelphis fabianii; and slightly smaller 

than specimens of Huaridelphis raimondii. Using the distance 

between the two mandibular condyles of Phocageneus venustus (USNM V 21039) as an estimate for bizygomatic width, 

the latter is significantly larger. At rostrum base, although 

the premaxilla is wider than the maxilla in dorsal view, it 

remains distant from the lateral margin of the rostrum, differing on this point from Notocetus and Squalodelphis. The 

right premaxillary foramen is located anterior (more than 25 

mm) to the level of the antorbital notch (Figure 2.14), still 

not as anterior as in Squalodelphis. The posterolateral sulcus 

is clearly distinct until a level beyond mid-length of the bony 

nares, laterally margining a transversely flat premaxillary sac 

fossa, the latter not being medially depressed. The right premaxilla does not significantly widen posterolaterally, but it 

displays a slightly thickened posterolateral corner, anterior to 

the posterior margin of the bony nares. From this corner, the 

bone narrows markedly and extends posteromedially between 

the maxilla and nasal, either not contacting the frontal or 

contacting only its anterolateral corner. Lateral to the nasal, 

the surface of the premaxilla is excavated by a deep oblique 

groove (premaxillary cleft in Waipatia; Fordyce, 1994), laterally defined by the thickened lateral margin of the bone, as 

in several other squalodelphinids and platanistids (Lambert 

et al., 2014; Bianucci et al., 2018). The left premaxilla is lost 

along the bony nares, but the sutural marks on the underlying 

maxilla suggest it was wider than the right premaxilla, with a 

less defined posterolateral corner.

At rostrum base, the lateral margin of the maxilla is slightly 

convex. Both antorbital notches are V shaped and widely open 

anterolaterally, the right more so than the left (Figure 2.14A). On 

the right maxilla, at least one dorsal infraorbital foramen is located 

posteromedial to the antorbital notch, whereas a small foramen 

is present along the left premaxilla-maxilla suture just anterior to 

the antorbital notch. In the antorbital region, the maxilla does not 

completely cover the frontal anteromedially and anterolaterally; its 

dorsal surface makes a low dome, distinctly higher on the left side. 

In USNM PAL 475496, an oblique crest crosses this surface, which 

is absent in USNM PAL 310632. Along the vertex, two posterior 

dorsal infraorbital foramina are observed on each side, posterior to 

the corresponding premaxilla. An additional foramen is seen on the 
FIGURE 2.12. Phocageneus venustus. USNM V 21039. (A, B) Left mandible in medial and dorsal views, respectively. 

(C) Lingual view of the five posteriormost teeth in the left mandible. These teeth exhibit a medial rugose basal shoulder, 

that is ornamented with accessory cusps. The crowns of all of these teeth show wear facets on both mesial and distal 

faces. (D) Isolated anterior tooth. (E) Isolated tooth. Scale bar for C–E equals 10 mm.

7 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
NUMBER 107 • 7 5

right side, lateral and slightly posterior to the posterolateral corner 

of the premaxilla. The medial margin of the maxilla along the vertex is more erect on the right side, making a thick ridge. On the left 

side, the bone sends a longer, subtriangular, and transversely convex 

posteromedial projection. Furthermore, the left maxilla is considerably longer posterolaterally than the right, drawing an acute angle 

unlike the smooth curve observed on the right side (right side is 

more angled in USNM PAL 475496). This conspicuous asymmetry 

is reflected in the outline of the nuchal crest and is associated with a 

marked shift to the left of the sutures between the nasals and frontals on the vertex, as seen in all other squalodelphinids for which 

this region is preserved (see Bianucci et al., 2020).

The subtriangular nodular nasals are anteroposteriorly longer than wide, with a maximum width at their anterior margin 

(Figure 2.14A,C). This margin is concave, and the dorsal surface of each nasal slopes anteroventrally. Both frontals send an 

FIGURE 2.13. Phocageneus venustus. USNM V 21039. (A, B) Left periotic in ventral and dorsal views, respectively. (C) Left 

tympanic bulla in dorsal view. Elements whitened with sublimed ammonium chloride. Scale bar equals 10 mm.
7 6 • 

FIGURE 2.14. Squalodelphinidae indet. USNM PAL 310632, partial skull. (A) Dorsal view. (B) Right lateral view. 

(C) Anterodorsal view. In B and C, the rostral segments of the maxillae were not attached to the facial portion of the 

rest of the preserved skull. (D, E) USNM PAL 206286, right periotic in dorsal and ventral views, respectively. USNM 

PAL 206286 was reported by Muizon (1987: fig. 11) as Notocetus sp. Specimens whitened with sublimed ammonium 

chloride. Scale bar for D and E equals 10 mm.
NUMBER 107 • 7 7

anteromedial projection between the nasals (7 mm long for the 

left frontal). Contrasting with the nasals, the frontals are wider 

posteriorly; nasals plus frontals display an hourglass outline in 

dorsal view. Resulting from some degree of transverse constriction of the vertex at mid-length, such an hourglass outline and the 

anteroposteriorly long nasals differ from all other squalodelphinids for which this region is preserved (Furcacetus, Huaridelphis, 

Macrosqualodelphis, Medocinia, Notocetus, Squalodelphis, and 

USNM PAL 475496). The dorsal surface of the frontals slopes 

slightly less steeply anteroventrally than the surface of the nasals. 

The medial part of the supraoccipital wedges forward ever so 

slightly between the frontals.

The preorbital process of the frontal is thickened, more so 

on the left side (more than 26 mm as opposed to 21.5 mm on 

the right side). Each process is anteriorly pointed but shorter 

than in USNM PAL 475496 and Medocinia (see Muizon, 

1988a). The orbit is proportionally short (57 mm on right 

side), with a deeply concave roof. The robust postorbital process is triangular in lateral view and vertical. The infratemporal 

crest is well defined, except at mid-length, where it is markedly 

shallower. A shallow fossa, presumably for an extension of the 

pterygoid sinus in the orbit region, excavates the dorsal surface 

of the frontal groove from a level 25–30 mm from the lateral 

margin of the frontal. The lateral limit of this fossa is poorly 

defined, lacking the step observed in Huaridelphis and Notocetus; it extends far posteromedially, but it does not significantly 

deepen dorsally, differing from USNM PAL 475496. The roof 

of the temporal fossa may not have been completely covered by 

the frontal; indeed, a large window with well-defined margins 

is observed in the right frontal, leaving the maxilla exposed 

ventrally.

In the mesorostral canal, the presphenoid is anteriorly short 

(29.5 mm) and ovoid. The canal was originally widely open dorsally at rostrum base.

Remarks. On the basis of the preserved parts, USNM 

PAL 310632 differs from all other described squalodelphinids, 

especially at the level of the vertex (outline and proportions of 

the nasals). This specimen does not share clear synapomorphies 

with any of these taxa, suggesting membership in a different 

genus. Unfortunately, there is no overlap with preserved parts 

of Phocageneus venustus, and the only difference proposed is 

related to size (USNM PAL 310632 corresponds to a smaller 

individual than P. venustus USNM V 21039). Although USNM 

PAL 310632 most likely does not belong to the same species 

as USNM PAL 475496 (an Aurora Phosphate Mine specimen), 

more complete skulls will be necessary to determine their affinities. In conclusion, this specimen supports the hypothesis 

proposed by Muizon (1987) and based on periotic morphotypes that at least two squalodelphinid species were present in 

the lower part of the Calvert Formation. More complete skulls, 

including associated ear bones, teeth, and mandibles, would 

greatly facilitate comparisons between the different morphotypes as evidenced by skulls and periotics and allow for a more 

precise assessment of squalodelphinid diversity in the Early 

Miocene of the Calvert Formation. Recent discoveries from 

the Pisco Basin (Peru) reveal an even greater squalodelphinid 

diversity, with at least four species, during the Burdigalian in the 

southeastern Pacific (Bianucci et al., 2020).

Family Platanistidae Gray, 1863

Among extant odontocetes, the South Asian river dolphins 

Platanista gangetica and P. minor are the most unusual forms, 

characterized by highly derived morphological features (Braulik 

et al., 2021). Their eyes are vestigial (i.e., functionally greatly 

reduced), and their melon is partially surrounded by a parabolic 

bony hood lined with an air-filled sinus that is thought to act as 

an acoustic reflector (Boersma et al., 2017). These two closely 

related species inhabit discontinuous river systems in Pakistan, 

India, Nepal, and Bangladesh (Sinha et al., 2010; Braulik et 

al., 2021). Unfortunately, they have no fossil record (Fordyce, 

2009b). They are the sole surviving members of the Platanistidae. In spite of their present geographic isolation, during the 

Miocene, platanistids were more widespread geographically and 

found in marine, brackish, and freshwater deposits (Barnes et al., 

2010). Miocene platanistids are known from the North Atlantic, 

Paratethys, Amazon region, southeastern Pacific, and possibly 

even Korea and the North Pacific (Barnes, 2006; Lambert, 2006; 

Lambert et al., 2008; Lee et al., 2012; Bianucci et al., 2013, 

2020; Benites-Palomino et al., 2020a). Most Miocene platanistids had remarkably elongated rostra (up to 5 times longer than 

the facial region of the skull, except Araeodelphis) with a full 

complement of homodont teeth in both upper and lower jaws.

Five platanistids are known from the Miocene of the Chesapeake Group: Araeodelphis natator Kellogg, 1957; Grimadelphis 

spectorum gen. et sp. nov.; Zarhachis flagellator (Cope, 1868); 

Pomatodelphis inaequalis Allen, 1921; and Pomatodelphis 

santamaria sp. nov.

Araeodelphis natator Kellogg, 1957

FIGURES 2.15–2.17

Araeodelphis natator – Platanistidae

(Illustration by Brenna Litynski)

Kellogg (1957) named Araeodelphis natator from the Calvert Formation (Early Miocene, Burdigalian correlative) of the 

Calvert Cliffs, Maryland. The holotype comprises an associated 
7 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

rostrum and partial mandible of one individual. Kellogg referred 

to the species an associated partial skeleton that includes vertebrae and ribs. On the basis of the type specimen, Kellogg was 

unable to attribute this enigmatic species to a known odontocete 

family. On the basis of newly assigned specimens (CMM-V-9977 

and USNM PAL 526604), Araeodelphis natator is now referred 

to the Platanistidae (see Godfrey et al., 2017, for USNM PAL 

526604). These new specimens demonstrate that Araeodelphis

natator Kellogg, 1957 is the most stemward member of the Platanistidae. Araeodelphis natator has a suite of plesiomorphies 

providing a clearer picture of the cranial morphology for early 

Platanistidae.

Araeodelphis shares with other platanistids a series of morphological features that allow their distinction from the closely 

related squalodelphinids: more than 33 teeth per quadrant, a 

deep lateral groove on the mandible, and frontal and maxilla 

that contribute a thin, sharp edge to form the posterior margin 

of the antorbital notch.

Holotype. USNM V 10478, rostrum and symphyseal 

part of mandible, with 12 detached teeth (some of which are reillustrated here in Figure 2.16C,D). 

Type Locality. Calvert Cliffs, 1.6 km south of Chesapeake Beach, Calvert County, Maryland (Kellogg, 1957).

Horizon and Age. The holotype was excavated 

from an undetermined level of the Calvert Formation (late Early 

to Middle Miocene, Chesapeake Group). At the type locality, 

only the Plum Point Member of the Calvert Formation comprises 

the Miocene component of the cliffs.

Known Range. Fairhaven and Plum Point members 

(Popes Creek Sand to SZ 7, Aquitanian-Burdigalian) of the Calvert Formation.

Referred Material. CMM-V-9977, a nearly complete skull and left periotic (Figure 2.17) collected from the 

Popes Creek Sand unit in the Fairhaven Member of the Calvert 

Formation; USNM PAL 526604, a partial skull (Figures 2.15, 

2.16; bizygomatic width estimated at 179 mm) that was found 

2.4 m below SZ 8, which corresponds to the Burdigalian (late 

Early Miocene). Additional teeth collected from the Pungo River 

Formation in the Aurora Phosphate Mine (Aurora, North Carolina) were attributed to Araeodelphis natator by Whitmore and 

Kaltenbach (2008).

Diagnosis of Species. Diagnostic characters of 

Araeodelphis natator can be found in Kellogg (1957) and Godfrey et al. (2017).

Description. A periotic of Araeodelphis natator, 

belonging to specimen CMM-V-9977 (Figure 2.17B–D), is described here for the first time. The maximum anteroposterior 

length of this left periotic is 37.5 mm. Its maximum mediolateral width is 22.5 mm. The anterior process is about as long as 

the pars cochlearis. This process is drawn out into a conspicuous point that bifurcates into a lesser pointed process approximately 3.5 mm from the apex of the primary anterior process 

(Figure 2.17C). In ventral view, the anterior bullar facet forms an 

elongate shallow depression. On the medial side of the anterior 

process, a ventrally directed flange of bone (Figure 2.17B) encloses and encircles a longitudinal vascular trough (anterointernal sulcus). The dorsomedial side of this flange of bone is swollen 

into a conspicuous tubercle (Figure 2.17B). Posterior to the bullar facet and immediately anterior to the mallear fossa, the periotic is conspicuously notched to form the fovea epitubaria. The 

mallear fossa is a circular concavity medial to the pars cochlearis. 

Lateral to the mallear fossa, the periotic is drawn out to form the 

lateral tuberosity (Figure 2.17C). Medial to the mallear fossa is 

the subcircular opening of the fenestra ovalis. The external opening for the facial canal is approximately equidistant between the 

mallear fossa and the fenestra ovalis.

In ventral view medial to the aforementioned structures, the 

outline of the pars cochlearis approximates the shape of a coffee bean (Figure 2.17C). In medial view (Figure 2.17B), the pars 

cochlearis is seen to be compressed dorsoventrally. The posterior 

face of the pars cochlearis holds the ovoid opening of the fenestra rotunda. It is slightly larger in diameter than the fenestra 

ovalis. In a dorsal view of the periotic (partially visible in Figure 

2.17B), there are three prominent openings on the pars cochlearis: in ascending order of size, the aperture for the vestibular 

aqueduct (the endolymphatic duct), the aperture for the cochlear 

aqueduct, and the internal acoustic meatus. The aperture for the 

vestibular aqueduct is remarkably small and slit-like, the aperture for the cochlear aqueduct is nearly circular in outline, and 

the internal acoustic meatus is teardrop shaped (Figure 2.17D). 

Within the internal acoustic meatus, four other notable features 

are clearly visible: (1) the proximal opening of the facial canal 

in the narrow anterior opening of the teardrop and (2) the oval 

foramen singulare bounded medially by the transverse crest, adjacent to which is (3) the circular spiral cribriform tract and posterior to which is (4) the area cribrosa media. Posterolateral to 

the aperture for the vestibular aqueduct, there is a prominence 

that extends toward the posterior process of the periotic.

Posterior to the fenestra ovalis is the cylindrical fossa for the 

stapedial muscle. Between it and the mallear fossa is the hiatus 

epitympanicus. Posterolateral to the fossa for the stapedial muscle is the anteroposteriorly elongate posterior bullar facet that 

presents a smooth surface. From the posterior pointed margin of 

the posterior bullar facet, a sharp keel marks the dorsal side of 

the posterior process. A spur-shaped articular process marks the 

lateral side of the posterior process of the periotic (a platanistoid 

trait).

Remarks. A close relative to Araeodelphis natator has 

been recently described from the Burdigalian of the Pisco Basin 

(Peru), but the fragmentary state of the specimen prevents us 

from knowing whether it belongs to a large specimen of that 

species, to a larger species of the genus Araeodelphis, or to a 

currently undescribed genus of an early diverging platanistid (Bianucci et al., 2020).

Araeodelphis is unique among platanistids: although it had 

elevated supraorbital regions of the skull, these eminences did 

not consist of thickened bone as in Zarhachis (see below), nor 

were they pneumatized as in Platanista gangetica (Boersma et 
NUMBER 107 • NUMBER 107 • 7 9

FIGURE 2.15. Araeodelphis natator. (A) Referred specimen, USNM PAL 526604, skull in dorsal view. Skull whitened with 

sublimed ammonium chloride. (B) Restoration of the skull in dorsal view. Modified from Godfrey et al. (2017).
FIGURE 2.16. Araeodelphis natator. (A) Referred specimen, USNM PAL 536604, skull in left lateral view. Placement 

of left zygomatic process of the squamosal approximate. (B) Restoration of the skull in left lateral view. (C) Isolated 

teeth from the holotype specimen of Araeodelphis natator: (1, 2) mesial and distal views of anterior teeth and (3, 4) 

lingual to mesiolingual views of posterior teeth. These images are reproduced from original photographs taken by 

Kellogg (1957: plate 18), reedited here in Adobe Photoshop. Teeth whitened with sublimed ammonium chloride. 

Scale bar for C equals 10 mm. (D) Right dorsolateral view of the anterior end of the rostrum of the holotype, USNM 

V 10478. A, B, and C modified from Godfrey et al. (2017).

8 0
NUMBER 107 • 81

FIGURE 2.17. Araeodelphis natator. (A) Referred specimen, CMM-V-9977, skull in dorsal view. (B–D) CMM-V-9977, 

left periotic in medial, ventral, and dorsal views, respectively. Specimen whitened with sublimed ammonium chloride. 

Scale bar for B–D equals 10 mm.
al., 2017). Araeodelphis did possess an air-filled fossa for the 

orbital lobe of the pterygoid sinus, as observed in several squalodelphinids, but that fossa did not open dorsal to the frontal 

between the frontal and maxilla as in Zarhachis (Barnes et al., 

2010). Araeodelphis also possessed one of the smallest olfactory 

bulb chambers of any odontocete (2 × 7 mm long). Therefore, it 

may have retained some degree of olfactory ability, albeit greatly 

reduced compared to most terrestrial mammals.

In recent phylogenetic analyses, Araeodelphis was recovered 

as a platanistid branching before the node Platanistinae + Pomatodelphininae (Godfrey et al., 2017; Bianucci et al., 2020).

Kellogg (1957) referred USNM V 16569 (consisting of 6 

cervicals, not including the atlas; 10 dorsal and 5 lumbar vertebrae; and 11 ribs) to Araeodelphis natator. Kellogg came to that 

conclusion on the basis of a process of elimination, and he may 

well have been correct, although in the absence of overlapping 

elements or morphologies, we proceed with greater caution.

Platanistidae indet.

Grimadelphis gen. nov.

FIGURES 2.18–2.20

Most of the skull of a platanistid (CMM-V-9941, Figures 

2.18–2.20) was found in Popes Creek Sand, Fairhaven Member, 

Calvert Formation. This specimen preserves a sufficient number 

of features that differ from those of other platanistids to warrant 

naming a new basal Calvert Formation genus and species.

Type and Only Known Species. Grimadelphis 

spectorum sp. nov.

Etymology. The generic epithet Grimadelphis honors Kyle Grimsley and Gary Grimsley, who found, collected, and 

prepared the holotype skull and then donated it to the CMM. 

The family name “Grimsley” is from the Old English words 

grima and leah, meaning a forest or clearing haunted by a specter or goblin (Mills, 1991). Grima was combined with delphis

(dolphin in Greek), meaning “a fish with a womb,” to form 

Grimadelphis.

Diagnosis. As for the type and only referred species.

Grimadelphis spectorum sp. nov.

Holotype. CMM-V-9941 preserves the posterior rostral section of the skull, part of the facial region, squamosals, 

and the occipital condyles (Figures 2.18–2.20). The supraorbital 

processes of the frontals were not preserved.

Type Locality. Miocene age sediments about 4.8 m 

above the base of the cliff along the Popes Creek section of the 

cliffs in Charles County, Maryland, north-northwest of the Nice/

Middleton Bridge (i.e., Highway 301, Potomac River Bridge).

Horizon and Age. Popes Creek Sand unit within 

the Fairhaven Member of the Calvert Formation. Early Miocene.

Known Range. Popes Creek Sand, Fairhaven Member (Burdigalian), Calvert Formation.

Etymology. To create the specific epithet spectorum, 

“er” was removed from “specter” (for ease of pronunciation), 

which in turn was taken from the aforementioned Old English 

meaning of Grimsley. “Orum” was then added as a suffix to 

“spect” according to the ICZN guidance (International Commission on Zoological Nomenclature, 1999) for a species name that 

among other conditions, honors more than one person, in this 

case Kyle Grimsley and Gary Grimsley.

Referred Material. None at this time.

Diagnosis of Species. Grimadelphis spectorum is a 

member of Platanidelphidi (sensu Bianucci et al. 2020) because 

the posterior dorsal infraorbital foramen is more medial than the 

lateralmost margin of the premaxilla, the dorsal margin of the zygomatic process is convex in lateral view, and the ventral margin 

of the zygomatic process is almost straight. It is a member of Platanistidae because of the posterolateral expansion of the premaxilla in the supraorbital region; more complete specimens will be 

needed to further test affinities within platanistid subfamilies. It 

differs from Araeodelphis, Pomatodelphis, and Zarhachis in the 

presence of occipital protuberances and from Z. flagellator in not 

having a hemispherical vertex; in having symmetrical premaxillae 

in dorsal view anterior to the antorbital notch; in having larger 

premaxillary foramina positioned farther forward on the rostrum 

(in Z. flagellator, the premaxillary foramina are at the level of the 

antorbital notch); in having an occipital shield that is more inclined 

anteriorly such that the vertex lies at the level, or anterior to a line 

drawn, in dorsal view, between the anterior margin of the right 

and left zygomatic processes of the squamosals; in having mandibular fossae that are much less transversely concave; in having 

much more deeply incised sternocephalicus fossae; and in having 

a larger and proportionately anteroposteriorly thicker postglenoid 

process. It differs from Prepomatodelphis in lacking a bifurcated 

posterior end of the premaxilla, in having a more laterally directed 

lateral portion of the nuchal crest (instead of posteriorly directed), 

and in the zygomatic process being not as deep dorsoventrally in 

its posterior portion. It differs from P. inaequalis in having symmetrical premaxillae anterior to the level of the antorbital notch 

(in P. inaequalis the premaxillae are conspicuously asymmetrical 

in this region); in having a larger premaxillary foramen; in having a more dorsoventrally slender and elongate zygomatic process 

(in P. inaequalis the zygomatic process is very compressed bilaterally and dorsoventrally deep); in having a less concave mandibular fossa with a proportionately much more robust postglenoid 

process; in having a much more pronounced and deep sternocephalicus fossa; in having an occipital shield that is more inclined 

anteriorly (in P. inaequalis, the occipital shield is nearly vertical); 

and, in a palatal view of the skull, in having a forward positioned 

infraorbital foramen lateral to the positioning of the palatines. 

It differs from Pomatodelphis bobengi, at least in the position of the premaxillary foramen (more anterior here) and the 

anteroposteriorly thicker postglenoid process. It differs from 

Pomatodelphis santamaria sp. nov. (see below) in having smaller 

8 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
 8 3

FIGURE 2.18. Grimadelphis spectorum gen. et sp. nov. (A) CMM-V-9941, holotype, partial skull just anterior to a true dorsal 

view. (B) Interpretive drawing of the same skull. Abbreviation: m. = muscle.
8 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.19. Grimadelphis spectorum gen. et sp. nov. CMM-V-9941, holotype, partial skull. (A) Right lateral view. (B) 

Ventral view. (C) Left ventrolateral view showing the location of the ventral carotid foramen, among other anatomical 

features.
NUMBER 107 • 8 5

FIGURE 2.20. Grimadelphis spectorum gen. et sp. nov. CMM-V-9941, holotype, partial skull. (A) The right otic region in 

ventral view. (B) Interpretive drawing of the same.
8 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

frontals exposed on the vertex, in having a much thinner supraoccipital rim that abuts the frontals on the vertex, in having very differently shaped zygomatic processes and less concave mandibular 

fossa, in having an occipital shield that is more inclined anteriorly 

(in P. santamaria sp. nov., the occipital shield, as in Zarhachis and 

other Pomatodelphis species, is nearly vertical), and in lacking the 

cylindrical deep fossa/foramen in each exoccipital. It differs from 

the extant Platanista in, among others, the lack of the bony hood 

(high maxillary crests) surrounding the melon, the rostrum being 

transversely wider in its proximal region, its vertex not being as 

transversely pinched as in Platanista, and its occipital shield being 

proportionally much broader.

Description. The only known specimen (CMM-V9941) consists of a single partial skull preserving the posterior 

part of the rostrum and the facial region less the supraorbital 

processes. Unfortunately, the ear bones, teeth, and mandibles 

were not preserved. Nevertheless, those parts of the skull that 

remain are very well preserved in three dimensions with visible 

sutures in most places. That portion of the rostrum that is preserved gives every indication that Grimadelphis spectorum had 

an elongated rostrum as in pomatodelphinines, but in its absence, we cannot be certain of just how long it was.

Premaxilla. From those parts of the premaxillae 

that are preserved, they appear to have been symmetrical, especially anterior to the premaxillary foramina. This is somewhat 

surprising because in the Platanidelphidi (which includes the 

squalodelphinids; see Bianucci et al., 2020:7) the widths of the 

premaxillaries are conspicuously different when seen in dorsal 

view. The premaxillary foramen is seemingly hypertrophied in 

CMM-V-9941 (Figure 2.18), positioned anterior to the antorbital notch and immediately adjacent to the mesorostral canal 

in the ventralmost part of each premaxilla. The left premaxillary foramen lies anterior to the right foramen. These foramina mark the anterior reach of the bold posterolateral sulci, 

which remain visible nearly to the posteriormost margin of the 

premaxilla. The premaxillae do not abut medially in the sections that are preserved in CMM-V-9941. Nevertheless, contralateral sides do increasingly approach each other anteriorly 

and suggest that they may have abutted over the mesorostral 

canal farther forward, had more of the rostrum been preserved. 

A wide suture separates the lateral margin of the premaxillae 

from the maxillae on the rostrum. Not enough of the rostrum is 

preserved to evaluate the presence of a lateral groove. Posterolaterally, the premaxillae form wide strap-like bands of bone 

that reach posteriorly to the level of the nasals. Posteriorly, the 

margin of the premaxilla remains wide to form a square termination, a feature also present in Araeodelphis, Pomatodelphis,

and Zarhachis. A medial ridge on the maxilla appears to prevent the posteromedial margin of the premaxilla from making 

contact with the nasal.

Maxilla. Posteromedially, the maxillae embrace 

the vertex comprising the nasals anteriorly and frontals posteriorly. Lateral to the vertex, each maxilla is perforated by a 

single posterior dorsal infraorbital foramen (close to the suture 

with the posteriormost margin of the premaxilla, a feature also 

present in Araeodelphis, Zarhachis, and Pomatodelphis). In the 

supraorbital region, the maxillae are not well preserved, so their 

contribution to the formation of a supraorbital eminence (as in 

Zarhachis and Pomatodelphis), if any, is unknown. Ventrally, 

the maxillae embrace the vomer, which is visible dorsally within 

the mesorostral canal and ventrally as a thin ridge medially. In 

ventral and lateral views of the skull (Figure 2.19), just anterior 

to the level of the antorbital notch, each maxilla is perforated by 

a large anteroposteriorly elongated ventral infraorbital foramen. 

This feature appears to be unique to Grimadelphis, as least compared to Araeodelphis, Zarhachis, and Pomatodelphis. Ventral 

to this large foramen, each maxilla hosts a V-shaped fossa that 

in life held the anterior reach of the pterygoid sinus, which extended anteriorly beyond the level of the antorbital notch.

Nasal. In dorsal view (Figure 2.18), each nasal is approximately square in outline and ever so slightly inflated. Together, 

they form the posterior margin of the bony nares and in so doing 

overhang the cribriform plate and the crescentic foramina.

Frontal. The frontals are not preserved sufficiently in 

the supraorbital region to know what contribution they might 

have made to a supraorbital eminence. On the vertex, the frontals lie in the same plane as the nasals, but with less exposure, 

and wedge out on the lateral margin between the maxillae posterolaterally and the supraoccipital posteriorly. Ventrally, the 

frontals preserve the infratemporal crest (Figure 2.19B).

Squamosal. Both squamosals are well preserved in 

CMM-V-9941 (Figures 2.18–2.20). In dorsal view, they present a wide profile anteriorly, unlike in other platanistids, in 

which the squamosals are more slender anteriorly. In a lateral 

view of CMM-V-9941, the squamosal tapers evenly anteriorly 

to a rounded point. This morphology is very unlike the usual 

platanistid squamosal profile, which in lateral view is very deep 

dorsoventrally, not tapering to a point anteriorly. The posterolateral margin of the squamosal presents a deep sternocephalicus fossa that passes posteroventrally onto the exoccipital. In 

ventral view, the squamosal presents a shallow, slightly transversely concave mandibular fossa, quite unlike the more nearly 

vertical fossa in Araeodelphis, Pomatodelphis, and Zarhachis. 

Medial to the anteroposteriorly thick postglenoid process is 

the 14 mm wide tympanosquamosal recess (Figure 2.20). Ventromedial to this recess is the thin platelike falciform process 

of the squamosal. The ridge that forms the falciform process 

continues posteriorly to terminate where it intersects the spiny 

process of the squamosal. Posterior to the spiny process is a 

pronounced cuboid prong of bone, the posttympanic process 

that projects posteroventrally toward the base of the paroccipital process (Figure 2.20). This prong of bone is present on the 

right side of the skull but was broken off on the left-hand side. 

On the right-hand side of the skull, the prominent posttympanic process descends in parallel with the paroccipital process, 

but they do not abut distally.

Vomer. In ventral view (Figure 2.19), the posterior 

margin of the vomer has become detached from the basioccipital 
NUMBER 107 • 8 7

as a result of mild postmortem distortion. Anterior to this point, 

the vomer presents as a very thin and ventrally projecting medial 

ridge, the vomerine crest/nasal septum. Dorsally, it is clasped 

bilaterally by the presphenoid. As the vomerine ridge passes 

forward ventromedially, it becomes hidden by the maxillae that 

abut ventrally in the region of the aforementioned large ventral 

infraorbital foramina. The vomer reappears as a thin crest of 

bone between the maxillae farther forward on the ventral side 

of the rostrum.

Supraoccipital. The supraoccipital is roughly semicircular in outline when viewed perpendicular to the plane of 

the bone. Dorsomedially, the bone preserves a vertical ridge (external occipital crest) descending from the vertex (Figure 2.18), 

showing that the frontals and nasals on the vertex are significantly offset to the left-hand side of the skull, as in other platanistoids (sensu Bianucci et al., 2020). Lateral to this midline crest 

are two prominent swellings of bone, presumed to be the site of 

origin of the semispinalis muscle. Most of the occipital shield is 

inclined at an angle of between 45° and 50° from the horizontal, 

much more forwardly inclined than in other platanistids.

Exoccipital. The 88 mm wide occipital condyles are 

set off on a distinct condylar neck (Figures 2.18, 2.19) and are 

prominent and proportionally large (the ratio between the width 

of the condyles and the bizygomatic width is 0.44). Relatively 

deep condyloid fossae are present both dorsally and ventrally. 

In both dorsal and ventral views, the paroccipital processes are 

robust (Figure 2.20). Immediately adjacent to the jugular notch, 

the ventral end of the paroccipital process is thickened, terminating in a roughly circular outline in ventral view and set apart by 

a short neck from the more lateral portion of the exoccipital.

Basioccipital. Beginning at the jugular notch, the 

ventrolaterally diverging basioccipital crests converge slightly 

toward the midline as they extend forward for a distance of approximately 47 mm (Figure 2.19B). The basioccipital basin is 

evenly smooth and devoid of fossae or tubercles. At about the 

midpoint in its height, the basioccipital crest is approximately 10 

mm thick. On the dorsolateral surface of the basioccipital crest 

near the anterior end of the periotic fossa is the 2 mm oval opening of the ventral carotid foramen (Figure 2.19A). Approximately 

9 mm dorsal to the carotid foramen is a trough (the path for the 

mandibular nerve) leading into the foramen ovale. The pharyngeal crests of the pterygoids were not preserved, and there is no 

obvious separation between the basioccipital and the basisphenoid in CMM-V-9941.

Remarks. Grimadelphis exhibits several stem features 

for platanistids, including (1) apparently symmetrical premaxillae anterior to the two premaxillary foramina, (2) a forwardsloping supraoccipital so that the occipital shield faces forward 

at an angle of about 45°–50° relative to the long axis of the skull 

(in other platanistids, including Araeodelphis, the supraoccipital 

is nearly vertical), and (3) zygomatic processes that are reminiscent of those in Eurhinodelphinidae, not bilaterally compressed 

and dorsoventrally deep as in other platanistids.

Subfamily Pomatodelphininae Barnes, 2002

Type Genus. Pomatodelphis Allen, 1921.

Other Referred Genera. Prepomatodelphis

Barnes, 2002 and Zarhachis Cope, 1868.

Diagnosis. Diagnostic characters of Pomatodelphininae can be found in Barnes (2002, 2006) and Bianucci et al. 

(2013).

Zarhachis flagellator Cope, 1868

FIGURES 2.21, 2.22

Zarhachis flagellator — Platanistidae

(Illustration by Tim Scheirer)

Holotype. An anterior caudal vertebra, ANSP 112321 

(Cope, 1868; Kellogg, 1924a). Although the holotype is most 

likely not diagnostic and does not overlap with later referred 

specimens, the genus and species names Zarhachis flagellator have 

been associated for a long time with the cranial specimens later 

referred to this taxon by Kellogg (1924a, 1926). Therefore, we 

prefer retaining the genus and species names, as was earlier proposed for Phocageneus venustus (see also Lambert et al., 2014).

Type Locality. Miocene marl of Charles County, 

Maryland (Kellogg, 1924a).

Horizon and Age. Calvert Formation, SZ unknown for the holotype, Early to Middle Miocene.

Known Range. SZ 5–17, for part or all of the Burdigalian, Langhian, and Serravallian.

Referred Material. CMM-V-2279, partial skull 

(Figure 2.21A), SZ 14, Calvert Formation; USNM V 10485, partial skeleton including a nearly complete skull (bizygomatic width 

= 268 mm) with partial periotic (Figure 2.21C,D) and tympanics, 

mandibles, sternum, hyoids, vertebrae, chevrons, ribs, and elements 

of the manus, collected close to Chesapeake Beach, SZ 5, Calvert 

Formation; USNM V 10850, squamosal, periotic, partial skull roof, 

and occiput, SZ 8, Calvert Formation; USNM V 10911, partial 

skull (bizygomatic width = 260 mm) including the neurocranium 

and rostrum base, SZ 6–8, Calvert Formation; USNM V 13768, 

skull, SZ 17, Choptank Formation; USNM V 16633, rostrum, 

lower jaw, axial elements, partial rib, Calvert Formation; USNM 

V 23030, partial lower jaw, Calvert Formation; USNM V 23043, 
8 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

partial skull roof, Calvert Formation; USNM V 25168, skull roof 

and rostrum, SZ 12, Calvert Formation; USNM PAL 310625, periotic, Calvert Formation; USNM PAL 310627, skull, SZ 14, Calvert 

Formation; USNM PAL 449655, tympanic bulla, Fairhaven Member, Calvert Formation; and USNM PAL 453048, partial rostrum, 

Calvert Formation. Now that another platanistid is known from 

the Popes Creek Sand (i.e., Grimadelphis spectorum), we are not 

convinced that the aforementioned referred tympanic bulla (USNM 

PAL 449655) is without question that of Zarhachis flagellator. 

Diagnosis of Species. Diagnostic characters of 

Zarhachis flagellator can be found in Kellogg (1924a, 1926) and 

later works comparing this species with other platanistids (e.g., 

Barnes, 2002, 2006; Godfrey et al., 2017).

Remarks. On the medial side of the supraorbital lobes 

of the frontals in Zarhachis, a pterygoid sinus is seen to have 

invaded the space between the frontal and maxilla, resorbing 

some of the thickened layered bone of the frontal (Figure 2.22A; 

Barnes et al., 2010: fig. 9C). This supraorbital sinus created a 

small air-filled chamber that is presumed to have formed a more 

effective acoustic reflector than dense bone alone, anticipating 

the greatly expanded and air-lined parabolic acoustic reflectors 

present in Platanista (Boersma et al., 2017).

Zarhachis flagellator possesses one of the most impressively 

elongate snouts among mammals (Figure 2.21B; see McCurry 

and Pyenson, 2018). Both upper and lower jaws are the same 

length and hold evenly spaced pointed teeth throughout their antorbital length. With more than 300 teeth, Zarhachis (and Pomatodelphis, see below) can boast the highest tooth counts of any 

mammal. In relation to their dentition, if one shines raking light 

over the mandible or rostrum of Zarhachis or Pomatodelphis, 

embrasure pits are visible. They are internal to the tooth row 

on the left side of the mandible and right side of the rostrum, a 

feature also observed in pomatodelphinine rostral material from 

the Miocene of the North Sea (Lambert, 2006). Did they capture 

consistently on one side? Behavioral laterality is a commonly 

observed feature among cetaceans (e.g., Woodward and Winn, 

2006; Platto et al., 2017), and such a side preference may have 

occurred during predation among pomatodelphinines.

Genus Pomatodelphis Allen, 1921

Type Species. Pomatodelphis inaequalis Allen, 1921.

Other Referred Species Based on Diagnostic Cranial Material. Pomatodelphis bobengi (Case, 

1934), late Middle to earliest Late Miocene of Florida (see Morgan, 1994), Pomatodelphis stenorhynchus from the Burdigalian 

in France (Holl, 1829), and Pomatodelphis santamaria sp. nov. 

(see below).

Remarks. Although we describe a new species of Pomatodelphis, a revision of the genus is beyond the scope of this 

work (see, e.g., Barnes, 2002, 2006). Further work is needed, 

including the inclusion of the aforementioned species of Pomatodelphis in a phylogenetic analysis of Platanistoidea, together 

with other pomatodelphinines.

Pomatodelphis inaequalis Allen, 1921

FIGURES 2.23, 2.24

Holotype. MCZ 15750, a fragment of the right 

maxilla.

Type Locality. Amalgamated Phosphate Company 

Mine, Brewster, Polk County, Florida.

Horizon and Age. Bone Valley Member of the 

Peace River Formation. The species occurs in the lower part 

of the formation, the Agricola and Bradley faunas, late Middle 

Miocene (Serravallian) (Morgan, 1994). In Maryland, specimens 

are found in the upper part of the Calvert Formation and the 

lower part of the Choptank Formation, Middle Miocene.

Known Range. SZ 12–17, the upper part of the Calvert Formation and the lower part of the Choptank Formation 

(Langhian–Serravallian).

Referred Material. CMM-V-3915, incomplete 

skull (bizygomatic width = 248 mm; Figure 2.23A), SZ 12, Calvert Formation; USNM V 13768, partial neurocranium including periotics (Figure 2.24C,D), Calvert Beach, SZ 17, Choptank 

Formation; USNM PAL 187414, incomplete skull (bizygomatic 

width = 215 mm) (Figure 2.24A,B), Drumcliff Member, SZ 17, 

Choptank Formation. 

Diagnosis of Species. Pomatodelphis inaequalis differs from P. bobengi in its smaller size, comparatively longer and 

narrower rostrum, and smaller teeth (Morgan, 1994). It differs 

from Pomatodelphis santamaria sp. nov. (see below) in its size 

being larger (bizygomatic width estimated at 190 mm in P. santamaria sp. nov. and 210–215 mm in P. inaequalis), nasal-frontal 

suture being roughly rectilinear to posteriorly concave, posterior 

wall of the nuchal crest along the vertex not being posteriorly convex in dorsal view, postglenoid process of the squamosal being 

significantly longer ventrally, pars cochlearis of the periotic being 

proportionally larger compared to the anterior process, aperture 

for the endolymphatic duct being less transversely elongated, and 

lateral tuberosity of periotic being shorter and less pointed.

Remarks. The shape of the supraorbital crests in Pomatodelphis inaequalis differs from those of Zarhachis in that 

they are not as erect (Boersma et al., 2017: fig. 9e). There is a 

hornlet on the frontal (Figures 2.23B, 2.24A) that is not present 

in Zarhachis. The top of the supraorbital crests usually exceeds 

the height of the vertex in Zarhachis (Figure 2.22B), whereas they 

are usually approximately equal in Pomatodelphis inaequalis. In 

spite of these differences, both pomatodelphinines had branches 

of the pterygoid sinus that extend up into the supraorbital process 

between the frontal and maxilla (Boersma et al., 2017). Boersma 

et al. (2017) proposed that the supraorbital crests in Pomatodelphis inaequalis might have been involved in sound production 

and propagation. They suggested that the internal surface could 

have contributed to reflecting sound waves generated by the phonic lips. Both dense bone and/or an air-filled sinus would reflect 

sound, but the degree to which the supraorbital crests and airfilled sinus contributed to this has yet to be determined.
NUMBER 107 • 8 9

FIGURE 2.21. Zarhachis flagellator. (A) CMM-V-2279, posterior rostrum and neurocranium, in dorsal view. 

(B) Restoration of the skull in dorsal view. (C, D) USNM V 10485, partial left periotic in ventral and dorsal views, 

respectively. Periotic whitened with sublimed ammonium chloride. Scale bar for C and D equals 10 mm.
9 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.22. Zarhachis flagellator. (A) Compiled computed tomography (CT) scan images sectioned transversely through the supraorbital processes of the frontals of the skull USNM V 10911. A pneumatic sinus is present on the medial side of the vertical face of the supraorbital process of the frontal. (B) CMM-V-2279, skull in left 

lateral view showing the greatly enlarged hornlike supraorbital process/eminence of the frontal. [(A) Modified by 

SJG from Barnes et al. (2010: fig. 9c) and used by permission from Nova Science Publishers, Inc.]
NUMBER 107 • 9 1

FIGURE 2.23. Pomatodelphis inaequalis. (A) CMM-V-3915, skull in dorsal view. (B) Restoration of the skull in 

dorsal view. In B, an attempt was made to compensate for postmortem distortion present in CMM-V-3915.
9 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.24. Pomatodelphis inaequalis. (A) USNM PAL 187414, facial region of the skull in left lateral view. 

(B) USNM PAL 187414, anterior end of the rostrum in left lateral view showing the swollen roots of the teeth. 

(C, D) USNM V 13768, right periotic in dorsal and ventral views, respectively. C and D whitened with sublimed 

ammonium chloride. Scale bar for C and D equals 10 mm.
NUMBER 107 • 9 3

Hundreds of pointed needlelike teeth right up to the front 

end of both jaws (Figure 2.24B) suggest specialization for feeding on small, slippery-bodied prey.

Pomatodelphis santamaria sp. nov.

FIGURES 2.25–2.27

During the compilation of this review, a second new species of Platanistidae was discovered, with specimens in both the 

USNM and the CMM.

Holotype. CMM-V-4669 (Figure 2.25A,B), a partial 

skull including most of the neurocranium (with the two periotics in situ, but without supraorbital processes) and the rostrum 

base, found by the late Mary Theresa (Fox) Gascon on 24 January 1987. 

Type Locality. Calvert Cliffs between Seahorse 

Beach and Driftwood Beach (Chesapeake Ranch Estates), Calvert County, Maryland. David Bohaska records in his field notes 

for 31 January 1987 that the skull came from “about 400 yards 

[i.e., 365 m] N. of start of cliffs N. of 1st Beach” (first beach 

would be Seahorse Beach).

Horizon and Age. Although the holotype was 

not found in situ, it is locally derived from the Little Cove 

Point Member (SZ 21–23) of the St. Marys Formation on 

the basis of the presence of Turritella-containing sediments 

infilling parts of the skull. At this location along Calvert 

Cliffs, Turritella-containing clayey sediments could derive 

from only the Little Cove Point Member. Early Late Miocene 

(Tortonian).

Known Range. SZ 22–23, Little Cove Point Member 

(Tortonian) of the St. Marys Formation. Therefore, Pomatodelphis santamaria constitutes the geologically youngest pomatodelphinine species from Calvert Cliffs and is most likely one of 

the youngest records (if not the youngest) of a marine platanistid 

worldwide.

Etymology. The species epithet santamaria honors the late Mary Theresa (Fox) Gascon for having found the 

holotype skull and for having donated it to the CMM. Serendipitously, the specific epithet also indicates that this species is 

currently known from only the St. Marys Formation.

Referred Material. USNM V 22500 (Figure 

2.26C), partial neurocranium with two periotics in situ, collected 

along Calvert Cliffs south of Cove Point, either Choptank Formation or (more likely) St. Marys Formation, latest Middle to 

early Late Miocene; USNM PAL 214759 (Figures 2.26A,B,D,E 

and 2.27), partial neurocranium (bizygomatic width estimated 

at 190 mm) with detached left periotic, tympanic bulla, and malleus. The preservation on both these crania is consistent with 

their derivation from the Little Cove Point Member of the St. 

Marys Formation; USNM PAL 447490, mandible fragment, St. 

Marys Formation; USNM PAL 464067, distal end of flattened 

rostrum, St. Marys Formation.

Diagnosis of Species. This medium-sized pomatodelphinine is characterized by an anteroventral slope of the dorsal surface of frontals and nasals on the vertex; greatly reduced 

nasals; an anterolateral extension of the dorsal exposure of the 

frontal on the vertex, which precludes or markedly reduces the 

nasal-premaxilla contact; a triangular exposure of the interparietal between the frontals and supraoccipital on the vertex; and a 

deep fossa on the anterior surface of the exoccipital (presumably 

for the posterior sinus).

It differs from Zarhachis flagellator in the vertex being 

roughly transversely flat and slightly anteroposteriorly convex; 

zygomatic process of the squamosal being markedly shorter, 

higher than long in lateral view; much reduced postglenoid 

process of the squamosal being significantly shorter ventrally 

than the exoccipital; anterior wall of pars cochlearis being flat 

(versus convex in Z. flagellator) in ventral view; lateral tuberosity of periotic being longer and more pointed; inner posterior 

prominence of tympanic bulla being longer; and anterolateral 

concavity on the tympanic bulla being deeper. It further differs 

from Pomatodelphis inaequalis in its size being smaller (bizygomatic width estimated at 190 mm in P. santamaria and 210–

215 mm in P. inaequalis), nasal-frontal suture being posteriorly 

convex (versus roughly rectilinear to posteriorly concave in 

P. inaequalis), posterior wall of the nuchal crest along the vertex 

being posteriorly convex in dorsal view, much reduced postglenoid process of the squamosal being significantly shorter ventrally than the exoccipital, pars cochlearis of the periotic being 

proportionally smaller compared to the anterior process, aperture for the endolymphatic duct being more transversely elongated, and lateral tuberosity of the periotic being longer and 

more pointed. It further differs from Pomatodelphis bobengi in 

its size being markedly smaller (bizygomatic width up to 290 

mm in the latter), nasal-frontal suture being posteriorly convex 

(versus roughly rectilinear in P. bobengi), pars cochlearis of the 

periotic being proportionally smaller compared to the anterior 

process, aperture for the endolymphatic duct being more transversely elongated, anteromedial corner of the anterior process 

not being pointed, lateral tuberosity of periotic being longer and 

more pointed, and articular process of the periotic being directed 

posteroventrally (instead of laterally).

Description. Three specimens (the holotype CMMV-4669, USNM V 22500, and USNM PAL 214759) preserve the 

facial or cranial region of the skull, although CMM-V-4669 is 

slightly more complete, preserving more of the rostrum (Figure 

2.25A,B).

Premaxilla. At the anterior end of CMM-V-4669, 

the premaxillae are transversely and anteroposteriorly convex, 

dipping down into the open mesorostral canal. In the three 

specimens, the lowest point along the premaxillae occurs where 

the premaxillary foramen enters the body of the bone, a decidedly concave basin forming in this region of the skull. Anterior 

to the large premaxillary foramen, the medial margin of the 

premaxilla is a thin and short blade, directed dorsomedially. 

This blade forms the medial wall of the anteromedial sulcus. 
9 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.25. Pomatodelphis santamaria sp. nov. (A, B) CMM-V-4669, holotype, facial region of a partial skull in dorsal 

and ventral views, respectively. (C) USNM PAL 214759, ventral view of the basicranium showing the left periotic in situ. (D) 

USNM PAL 214759, the same as in C, with tympanic bulla in situ. Specimens whitened with sublimed ammonium chloride.
NUMBER 107 • 9 5

FIGURE 2.26. Pomatodelphis santamaria sp. nov. (A) USNM PAL 214759, facial/cerebral region of the skull in dorsal 

view. (B) Interpretive drawing of A. (C) USNM V 22500 in dorsal view. (D) USNM PAL 214759 in anterior view. (E) 

USNM PAL 214759 in left lateral view. Skulls whitened with sublimed ammonium chloride.
9 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

The posterolateral sulcus is well defined at least until the midlength of the bony nares (Figure 2.26B). The right premaxillary 

sac fossa is roughly transversely flat in the holotype and USNM 

V 22500 but concave in USNM PAL 214759, with a sigmoidal anteroposterior outline (being slightly longitudinally convex anteriorly and concave posteriorly). The left premaxillary 

sac fossa of the holotype differs in being medially concave and 

laterally convex. Right and left premaxillary sac fossae nearly 

contact each other in the holotype, whereas they may have been 

somewhat more widely separated in USNM PAL 214759. The 

premaxillae form the margin of the nares, curving around the 

openings as wide, plate-like bones that posteriorly bracket the 

nasals and frontals. The wide posterior ends of the premaxillae 

are separated from the supraoccipital only by relatively narrow 

intervention of the maxillae and frontals (the right premaxilla 

is incomplete posteriorly on the holotype, but traces of the premaxilla-maxilla suture indicate a smoothly rounded posterolateral outline of the premaxilla). Better preserved in USNM PAL 

214759, the posterolateral part of the premaxilla is facing more 

laterally, separated from the anterodorsally facing medial part of 

the bone by an angle.

As in Araeodelphis, Zarhachis, and Pomatodelphis inaequalis, the premaxillae are very wide at the level of the vertex and 

broadly contact the frontals. The posterior dorsal infraorbital 

foramen (Figure 2.26) lies behind and below the premaxilla as in 

other platanistids, squalodelphinids, and closely related platanistoids (see Bianucci et al., 2020).

Presphenoid and Cribriform Plate. The 

T-shaped cribriform plate is well preserved in all three specimens. 

Posteriorly, its dorsal margin rises at least to the level of the nasals. A prominent anterodorsally directed point is formed by the 

dorsomedial margin of the plate. From that point, the nasal septum sweeps anteroventrally to separate the two narial passages. 

On the posterior face of the cribriform plate, on either side of 

this ridge, the crescentic foramen/dorsal nasal meatus curves into 

the body of the bone.

Nasal. Only partly preserved on the holotype and 

USNM V 22500, the nasals are inconspicuous bones, shorter and 

narrower than the frontals and anteromedially pointed, which 

contributes to a low and unremarkable vertex. The nasals are 

missing in USNM PAL 214759, giving every appearance that they 

simply fell out postmortem. The concavities where they were in 

life are very small; this is no doubt reflective of the diminutive 

size of the nasals in USNM PAL 214759, as in Araeodelphis, and 

suggestive of the even more diminutive and derived nasals in the 

extant Platanista. The suture between joined nasals and frontals 

is posteriorly convex, with an anteromedial wedge of the frontals 

observed only in USNM PAL 214759. The highest point at the 

back of the skull is formed by the nuchal crest. From there, the 

dorsal surface of the frontals and nasals slopes anteroventrally and 

is slightly anteroposteriorly concave in the two referred specimens, 

whereas it is slightly convex for its frontal part in the holotype.

Frontal. On the foreshortened vertex, the frontals 

are coarsely textured by linear furrows. In USNM PAL 214759 

FIGURE 2.27. Pomatodelphis santamaria sp. nov. USNM PAL 214759. (A, B) Left periotic in ventral and dorsal views, respectively. 

Specimen whitened with sublimed ammonium chloride. Scale bar equals 10 mm.
NUMBER 107 • 9 7

(Figure 2.26A,B) and USNM V 22500 (Figure 2.26C), a triangular and furrowed interparietal is clearly outlined between the 

two frontals and the supraoccipital. Because of the numerous 

furrows covering the frontals in the holotype, the outline of the 

presumed interparietal is more difficult to delineate.

Maxilla. At the rostrum base, the dorsal exposure of 

the maxilla is narrower than the premaxilla, the narrowest level 

being 50 mm anterior to the right premaxillary foramen in the 

holotype. In this specimen, one left dorsal infraorbital foramen 

is seen along the suture with the premaxilla just anterior to the 

left premaxillary foramen. Along the vertex, narrow wings of 

the maxillae border the frontals. Lateral to this and posterior to 

the premaxilla, the posterior dorsal infraorbital foramen opens 

anteroventrally into the maxilla.

Supraoccipital. The thick nuchal crest is asymmetric posterior to the frontals in the three described specimens, its 

posterior wall being posteriorly convex on the right side of the 

skull and roughly rectilinear on the left side. In addition, the 

vertex is shifted to the left relative to the midline of the supraoccipital. The supraoccipital gains wide exposure along the posterodorsal margin of the skull. The occipital shield is depressed 

just below the nuchal crest (Figure 2.26B); more ventrally, it 

becomes slightly convex transversely, corresponding to a moderately inflated brain cavity. In dorsal view, the low temporal 

crests are directed posterolaterally, extending posteriorly barely 

beyond the medial part of the shield. A small, but deep, dorsal 

condyloid fossa is observed in the holotype. The condylar neck 

is short, relative to the proportionally large occipital condyles.

Squamosal. Somewhat better preserved on the left side 

of USNM PAL 214759 (because of the presence of the zygomatic 

process of the squamosal), the low and short temporal fossa 

displays a triangular outline pointing posteroventrally in lateral 

view (Figure 2.26E). Its dorsal margin was most likely originally 

significantly lower than the level of the vertex of the skull. The 

inflated zygomatic process of the squamosal is short anteroposteriorly (less so than in Pomatodelphis inaequalis) but deep dorsoventrally, with a rounded outline in lateral view (Figure 2.26E). 

Its dorsal margin is thickened mediolaterally, below which its 

ventralmost margin thins to a sharp edge. Its medial surface is 

evenly concave. The posterolateral surface of the squamosal is 

excavated by a fossa for the sternocephalicus muscle, extending 

anterodorsally beyond the level of the postglenoid process. The 

latter forms an obliquely oriented, short, and flattened blade, 

which ends before the ventral margin of the exoccipital. The 

tympanosquamosal recess is deep and narrow along the posterior part of the transversely and anteroposteriorly concave mandibular fossa and on the medial wall of the postglenoid process. 

The falciform process is a wide and long plate contacting the 

dorsoventrally high lateral lamina of the pterygoid along a long 

suture. The somewhat laterally bulging sutural area is pierced by 

several foramina (=external openings of the foramen ovale sensu 

Mead and Fordyce, 2009; often named foramen pseudo-ovale in 

previous works), at least two on the left side and two to three on 

the right side in USNM PAL 214759. Dorsal to the spiny process 

(Figure 2.25C), a deep fossa corresponds to the subcircular fossa 

described by Muizon (1987) in various platanistoids (see comments in Viglino et al., 2018b). Posteromedial to this fossa, the 

anterior wall of the exoccipital is excavated by a fossa deepening dorsomedially and followed ventrolaterally by a wide groove 

up to the ventral margin of the exoccipital. With a maximum 

diameter of 8 mm on the left side of USNM PAL 214759 and 14 

mm on the left side of the holotype, this deep fossa is separated 

from the posterior lacerate foramen by only a thin wall. Also observed in Zarhachis flagellator (USNM V 10911), this fossa may 

correspond to a fossa for the posterior sinus, as such a sinus is 

proposed to be present in the extant Platanista gangetica (Fraser 

and Purves, 1960; associated with a shallower fossa).

Basioccipital. Ventrally, the basioccipital crests are 

thickened and coarsely textured along their ventrolateral border, 

only diverging moderately posterolaterally (Figure 2.25).

Periotic. Both periotics are in situ in USNM V 22500 

and the holotype (Figure 2.25B), immediately anterior to the 

deep fossa in the exoccipital’s anterior wall. The dorsal margin 

of the anterior process tightly contacts the concave ventromedial 

margin of the falciform process along its whole length. In USNM 

PAL 214759 (Figure 2.27), the left periotic is free from the skull 

and completely preserved. The anterior process is massive, being 

longer than the pars cochlearis and markedly dorsoventrally and 

transversely thickened, with a blunt apex and a subrectangular 

outline in lateral view. In Zarhachis flagellator (USNM V 10485), 

the anterior process is more pointed. The shallow anterior bullar facet turns moderately anteroventrally, more so than in Z. 

flagellator. The parabullary sulcus is deep and markedly curved. 

The pointed lateral tuberosity is long, extending laterally beyond 

the lateral surface of the anterior process and separated from 

the latter by a deep anteroexternal sulcus. The lateral tuberosity 

is less pointed in P. inaequalis and Z. flagellator. The anterior 

margin of the mallear fossa is thick and ventrally protruding. In 

the broad hiatus epitympanicus, the conspicuous articular process makes a posterolaterally directed, relatively thin and long 

plate, as in other platanistids (see Muizon, 1987). The short and 

narrow posterior bullar facet displays a smooth surface, turning 

posterolaterally and slightly ventrally. In medial/lateral view, the 

dorsal crest extends as a prominent dorsal bulge at the level of 

the aperture for the endolymphatic duct; this bulge is lower in P. 

inaequalis (USNM PAL 187414) and more similar in P. inaequalis (USNM V 13768, attributed to Zarhachis by Muizon, 1987). 

In ventral view, the proportionally small pars cochlearis displays 

a rounded outline, although its anterior wall draws a 90° angle 

with the medial margin of the anterior process. The anterior 

wall of the pars cochlearis is more convex in Z. flagellator. The 

aperture for the endolymphatic duct is transversely elongated, 

whereas the small aperture for the cochlear duct is circular. In the 

ovale internal acoustic meatus, the circular proximal opening of 

the facial canal is located anteromedially to the spiral cribriform 

tract. The crest separating the foramen singulare from the latter 

opening is slightly lower than the crest separating it from the 

proximal opening of the facial canal.
9 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Tympanic Bulla. Apart from its posterior process, 

the left tympanic bulla of USNM PAL 214759 is complete (Figure 2.25D). The anterior spine is long, followed laterally by a 

conspicuous anterolateral concavity (deeper than in Z. flagellator, USNM V 10485). In ventral view, the lateral margin of 

the bone is markedly convex, with a notch corresponding to the 

well-defined lateral furrow at two-thirds of its length. The median furrow is deep, medially margined by a high ventromedial 

crest and ending before the base of the anterior spine. The inner 

posterior prominence is slightly shorter than the outer prominence (the difference in length is greater in Z. flagellator, USNM 

V 10485, and Platanista), being separated from the latter by a 

deep interprominential notch. With only part of its outline preserved, the elliptical foramen was probably originally large. In 

medial view, the involucrum is high for most of its extent, with a 

maximum height at about mid-length and a gradual anteroventral descent of its dorsal margin from that point. The involucrum 

is proportionally lower in Z. flagellator. The thick sigmoid process is directed transversely. The outer lip is dorsally high, with 

only the sigmoid process being higher, similar to Pomatodelphis 

inaequalis (USNM PAL 187414).

On the malleus, the tubercule is longer than the head (bearing the facets for the incus). The manubrium is hooklike, as in P. 

inaequalis (USNM PAL 187414; see Muizon, 1987) but differing from Platanista, and the muscular process is located slightly 

lower along the tubercule.

Remarks. It would be informative to recover a more 

complete skull, one that would preserve (1) the supraorbital processes, which are presumed to have been relatively elevated, as 

in most other platanistids, on the basis of the way in which the 

three neurocrania are broken through the supraorbital process, 

and (2) the rostrum, which is presumed to also have been extremely elongated, dorsoventrally flattened, and bearing multiple 

teeth as in other members of the subfamily Pomatodelphininae.

Family Eurhinodelphinidae Abel, 1901

Eurhinodelphinidae comprise an extinct family of hyperlongirostrine odontocetes. They probably first appeared in the 

Oligocene, flourished during the Miocene, and then became extinct before the Messinian (Late Miocene) without giving rise 

to any other forms (Lambert, 2005a; Fordyce, 2009b; Marx et 

al., 2016; Lambert and Goolaerts, 2022). There is, to date, no 

consensus on the phylogenetic relationships of eurhinodelphinids, although closer relationships with the Early Miocene longirostrine dolphin Eoplatanista, platanistoids, ziphiids, or even 

delphinidans (e.g., Muizon, 1991; Fordyce, 1994, 2002; Lambert, 2005c; Geisler et al., 2012; Tanaka and Fordyce, 2016) 

have been proposed in the past. Coding multiple, well-known 

eurhinodelphinid species in a large character-taxon matrix would 

be needed to better support any of these hypotheses.

The most obvious features characterizing members of the 

family are the extreme elongation of their rostrum, specifically 

the anterior premaxillary portion thereof; the edentulous premaxillae; and a rostrum that significantly exceeds the length of 

the lower jaw (Figure 2.28; Kellogg, 1925a; Lambert, 2005a, 

2005c; Marx et al., 2016). The rostrum typically constituted 

approximately four-fifths of the condylobasal length of the 

skull (Kellogg, 1925a). Although Fordyce (2009b) observed 

that there are no modern ecological equivalents, Lambert 

(2005a) proposed—drawing upon morphological parallels 

between the rostra of extant river dolphins and eurhinodelphinids—that the edentulous anterior part of the rostrum was 

a sensitive burrowing probe used to forage for prey in coastal 

and possibly estuarine bottom sediments. Lambert (2005a) 

concluded that they were relatively slow-swimming shallowwater inhabitants. It is also not beyond the realm of possibility that their rostrum was used to slash through schools 

of fish to incapacitate them, as done by the living swordfish 

Xiphias gladius; the roughly circular cross section of the rostrum 

of eurhinodelphinids (differing from the dorsoventral flattening of X. gladius’s rostrum) suggests that movements to catch 

prey occurred in various directions, not only laterally (McCurry 

and Pyenson, 2018).

Eurhinodelphinid diversity seems to have reached its maximum during the Miocene Climatic Optimum (Lambert, 2005a). 

Locally, eurhinodelphinids are not known to occur above 

SZ 14 of the Calvert Formation (early Serravallian), whereas 

Xiphiacetus cristatus survived until the early Late Miocene (Tortonian) in the North Sea Basin (Lambert and Goolaerts, 2022).

Four species of eurhinodelphinids are currently recognized from the Miocene of the Chesapeake Group: Xiphiacetus 

bossi (Kellogg, 1925a), Xiphiacetus cristatus (du Bus, 1872), 

Schizodelphis morckhoviensis (du Bus, 1872), and Schizodelphis barnesi (Muizon, 1988a), listed here in descending order 

of abundance. Several other species were named in an unpublished Ph.D. dissertation (Myrick, 1979); some of them were 

tentatively synonymized with the species listed above (Muizon, 

1988a; Lambert, 2004, 2005a), but a detailed redescription 

and comparison of the very large sample housed at the USNM 

and CMM would be needed to clarify the eurhinodelphinid diversity in successive zones of the Calvert Formation (Lambert, 

2005a).

In some of the older literature (Gottfried et al., 1994, and 

references therein; Bohaska, 1998), the family Eurhinodelphinidae is referred to as the Rhabdosteidae (see Muizon, 1988a, 

for further details). Intrafamilial phylogenetic relationships have 

been preliminarily addressed in Lambert (2005a) and Benoit et 

al. (2011). Furthermore, in the older literature, Xiphiacetus from 

Calvert Cliffs is referred to as Eurhinodelphis, and Schizodelphis

is often referred to as Rhabdosteus (Kellogg, 1925a; Muizon, 

1988a; Whitmore and Kaltenbach, 2008).
NUMBER 107 • 9 9

Genus Xiphiacetus Lambert, 2005a

Type Species. Xiphiacetus cristatus (du Bus, 1872).

Other Referred Species. Xiphiacetus bossi (Kellogg, 1925a).

Xiphiacetus bossi (Kellogg, 1925a)

FIGURES 2.28, 2.29

Xiphiacetus bossi – Eurhinodelphinidae

(Illustration by Tim Scheirer)

Holotype. USNM V 8842 (Figure 2.29A), a partial 

skeleton including a nearly complete skull (bizygomatic width 

equals 240 mm) without ear bones, the mandible and teeth, 16 

vertebrae, 10 ribs, a scapula, a humerus, and part of the sternum. 

Type Locality. Approximately 3.2 km south of 

Chesapeake Beach, Calvert Cliffs, Calvert County, Maryland.

Horizon and Age. Plum Point Member of the Calvert Formation (SZ 5), which consists of a Burdigalian offshore siltstone.

Known Range along Calvert Cliffs. SZ 

3B–14 (Burdigalian to early Serravallian), Calvert Formation, 

although a specimen of X. cf. bossi from the Popes Creek Sand 

resides in a private collection (G. Grimsley, personal communication, 16 July 2020).

Referred Material. CMM-V-305, skull, SZ 12, 

Calvert Formation; CMM-V-347, skull, Fairhaven Member, Calvert Formation; CMM-V-886, skull, Fairhaven Member, Calvert 

Formation; CMM-V-1402, skull, SZ 4–9, Calvert Formation; 

CMM-V-1759, partial skull; CMM-V-1760, partial skull, SZ 12, 

Calvert Formation; CMM-V-1936, skull with mandible; CMMV-2278, skull, SZ 3B, Calvert Formation; CMM-V-2283, skull, 

teeth (Figure 2.29C), and ribs, SZ 13, Calvert Formation; CMMV-3686, skull, SZ 12, Calvert Formation; CMM-V-3730, skull, 

SZ 12, Calvert Formation; CMM-V-4260, skull, SZ 12, Calvert 

Formation; CMM-V-4068, skull, SZ 4–9, Calvert Formation; 

CMM-V-4326, skull, Fairhaven Member, Calvert Formation; 

CMM-V-6424, skull, SZ 12, Calvert Formation; CMM-V-6617, 

skull, SZ 11, Calvert Formation; CMM-V-7590, skull, SZ 10, 

Calvert Formation; USNM V 10464, skull, SZ 5, Calvert Formation; USNM V 10711, skull, Calvert Formation; USNM V 

10714, skull, SZ 3B, Calvert Formation; USNM V 16581, skull 

and periotics (Figure 2.29D,E) with part of the postcranial skeleton, SZ 12, Calvert Formation; USNM V 16890, skull, SZ 13, 

Calvert Formation; USNM V 23216, skull with part of the postcranial skeleton, SZ 12, Calvert Formation; USNM PAL 171103, 

skull with part of the postcranial skeleton, SZ 14, Calvert Formation; USNM PAL 167629, skull with part of the postcranial skeleton, SZ 12, Calvert Formation; USNM PAL 187174, skull, SZ 

12?; and USNM PAL 167622, skull, SZ 12, Calvert Formation.

Additional specimens collected from the Pungo River Formation in the Aurora Phosphate Mine (Aurora, North Carolina) 

were attributed to Xiphiacetus sp. by Whitmore and Kaltenbach 

(2008). The species is also recovered from Miocene deposits in 

Belgium (Lambert, 2005a, 2005c).

Diagnosis of Species. Diagnostic characters of 

Xiphiacetus bossi can be found in Kellogg (1925a) and Lambert 

(2005a).

Remarks. Many eurhinodelphinid periotics are present 

in the collections of the CMM and USNM. However, Whitmore 

and Kaltenbach (2008) could find no consistent characters for 

identifying isolated periotics to the species level in Xiphiacetus

or Schizodelphis.

FIGURE 2.28. Skeletal restoration and possible body outline of Xiphiacetus bossi in a left lateral view. Body length approximately 3.5 m. 

Modified from Godfrey et al. (2018).
100 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.29. Xiphiacetus bossi. A. USNM V 8842, holotype, posterior third of skull in dorsal view. (B) Restoration of the skull in dorsal view. (C) Isolated teeth of CMM-V-2283. (D, E) USNM V 16581, right periotic in ventral 

and dorsal views, respectively. D and E whitened with sublimed ammonium chloride. Scale bars for C–E equal 10 

mm. Abbreviation: m. = muscle.
NUMBER 107 • 101

Xiphiacetus cristatus (du Bus, 1872)

FIGURE 2.30

Holotype. IRSNB 3234-M.361, partial skull lacking 

teeth, ear bones, and basicranium, associated with the seven cervical vertebrae, seven thoracic vertebrae, and several ribs (see 

Abel, 1902; Lambert, 2005a).

Type Locality. Antwerp, Belgium (see Lambert, 

2005a, for details).

Horizon and Age. No data are available for the 

holotype. Other specimens from Belgium and the Calvert Formation (Plum Point Member, SZ 12–14) are dated from the 

Middle to early Late Miocene and Middle Miocene, respectively (see Lambert, 2005a; Lambert and Goolaerts, 2022; see 

also below).

Known Range along Calvert Cliffs. SZ 12–14 

(Langhian to early Serravallian), Calvert Formation.

Referred Material. CMM-V-884, skull, Calvert 

Formation; CMM-V-4325, skull, Calvert Formation; CMMV-4518, disarticulated skull, Calvert Formation; CMM-V5387, skull, SZ 14, Calvert Formation; USNM V 13436, 

skull, SZ 14, Calvert Formation; USNM V 13470, skull, SZ 

14, Calvert Formation; USNM V 21303, complete skull with 

teeth, SZ 13, Calvert Formation; USNM V 21360, rostrum, 

partial braincase, periotic, and atlas, SZ 13, Calvert Formation; USNM V 21363 (Figure 2.30A; bizygomatic width = 275 

mm), skull, SZ 14, Calvert Formation; USNM V 24856, skull, 

SZ 12, Calvert Formation; USNM V 25666, skull with part 

of the postcranial skeleton, SZ 12; USNM PAL 167675, skull, 

SZ 12–13, Calvert Formation; USNM PAL 171067, neurocranium, SZ 12, Calvert Formation; USNM PAL 244401, skull, 

SZ 14, Calvert Formation; and USNM PAL 244411, skull, SZ 

14, Calvert Formation. Lambert (2005a) referred 16 specimens 

from the Miocene of Belgium to X. cristatus. 

Diagnosis of Species. Diagnostic characters of 

Xiphiacetus cristatus can be found in Lambert (2005a).

Remarks. The skull of X. cristatus is one of the easiest to recognize if it preserves the area around the vertex. The 

reason is that both maxillae form cornua (small “hornlets”) 

adjacent to the vertex where the maxillae abut the frontals 

(Figure 2.30B). No other known odontocete possesses such 

maxillary cornua.

Genus Schizodelphis Gervais, 1861

Type Species. Schizodelphis sulcatus (Gervais, 1853).

Other Referred Species. Schizodelphis barnesi

(Muizon, 1988a) and S. morckhoviensis (du Bus, 1872).

Schizodelphis morckhoviensis (du Bus, 1872)

FIGURE 2.31

Schizodelphis morckhoviensis – Eurhinodelphinidae

(Illustration by Tim Scheirer)

Holotype. IRSNB 3235-M.343, a well-preserved 

skull (bizygomatic width = 187 mm), associated with the left 

periotic and a fragment of left tympanic bulla, lacking the anterior part of the rostrum, teeth, and fragments of the basicranium 

(see Abel, 1902; Lambert, 2004).

Type Locality. The holotype was found in Antwerp, 

3e section, northeast of the 4e section, where the holotype of Eurhinodelphis longirostris was found, along the present motorway 

around the city (Lambert, 2004).

Horizon and Age. No data are available for the 

holotype. The tympanic bulla of IRSNB M.1859 was found in 

the Antwerpen Sands, late Early to Middle Miocene (Louwye et 

al., 2000). 

Known Range along Calvert Cliffs. SZ 3B–13, 

Fairhaven and Plum Point Members (Burdigalian–early Serravallian) of the Calvert Formation.

Referred Material. CMM-V-248, skull, SZ 

12, Calvert Formation; CMM-V-2294, skull, SZ 3B, Calvert 

Formation; CMM-V-3958, skull, SZ 13, Calvert Formation; CMM-V-4070, partial skull, SZ 11, Calvert Formation; 

CMM-V-4481, skull, SZ 10–11, Calvert Formation; CMM-V4537, skull, SZ 10, Calvert Formation; CMM-V-4750, skull, 

lower jaw, and two tympanic bullae, SZ 12, Calvert Formation; CMM-V-5082, partial skull, SZ 8, Calvert Formation; 

CMM-V-6559, skull, SZ 12, Calvert Formation; USNM V 

21291, skull (Figure 2.31A) and periotic (Figure 2.31C,D), 

SZ 3B, Calvert Formation; USNM PAL 167676, skull, SZ 12, 

Calvert Formation; and USNM PAL 187306, skull, SZ 11, 

Calvert Formation. 

The partial skull IRSNB 3239-M.345 and the tympanic 

bulla with malleus associated with IRSNB M.1859, both from 

the Antwerp area (Belgium), are also referred to the species 

(Lambert, 2004).

Diagnosis of Species. Diagnostic characters of 

Schizodelphis morckhoviensis can be found in Lambert (2004) 

and Benoit et al. (2011).

Remarks. The postcranial skeleton of S. morckhoviensis remains unknown.
102 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.30. Xiphiacetus cristatus. (A) USNM V 21363, skull in dorsal view. (B) Restoration of the skull in 

dorsal view. Abbreviation: m. = muscle.
NUMBER 107 • 103

FIGURE 2.31. Schizodelphis morckhoviensis. USNM V 21291. (A) Facial portion of the skull in dorsal view. (B) 

Restoration of the skull in dorsal view. (C, D) Right periotic in ventral and dorsal views, respectively. Scale bar for 

C and D equals 10 mm.
104 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Schizodelphis barnesi Muizon, 1988a

FIGURE 2.32

Schizodelphis barnesi is an odontocete with typical eurhinodelphinid cranial proportions. It is known only from specimens collected along Calvert Cliffs. This eurhinodelphinid was 

formally recognized by Muizon (1988a) and reviewed most recently by Lambert (2004). Earlier, Myrick (1979) had named this 

new species within the genus Rhabdosteus (along with several 

others), but because his dissertation was never published, these 

species could not be formally adopted.

Lectotype. USNM PAL 244403 (by present designation), skull (Figure 2.32; bizygomatic width = 205 mm) with 

partial postcranial skeleton including atlas, axis, three other cervicals, four thoracics, manubrium, and pectoral elements, collected in SZ 12, Calvert Formation. 

Type Locality. Calvert Cliffs, Calvert County, 

Maryland.

Horizon and Age. SZ 12 of the Calvert Formation, 

early Middle Miocene.

Known Range. SZ 4–14, Plum Point Member (Burdigalian to early Serravallian) of the Calvert Formation.

Referred Material. CMM-V-18, skull, SZ 4–9, 

Calvert Formation; CMM-V-316, skull, SZ 14, Calvert 

Formation; USNM PAL 187312, skull, axial, and appendicular 

elements, SZ 14, Calvert Formation; USNM PAL 187317, skull, 

SZ 13, Calvert Formation; and USNM PAL 187624, skull, SZ 

12, Calvert Formation.

Also found in the Calvert Formation and previously referred to Schizodelphis barnesi (Muizon, 1988a: fig. 2; Benoit 

et al., 2011), the specimen MNHN AMN 19 is here referred 

to Schizodelphis sp., pending reassessment of the systematic status of USNM specimens of Schizodelphis not attributed here to 

Schizodelphis morckhoviensis or S. barnesi.

Diagnosis of Species. Diagnostic characters of 

Schizodelphis barnesi can be found in Lambert (2004).

Remarks. As part of Lambert’s (2004) review of European eurhinodelphinids, he studied the other genera within the 

family that occur along Calvert Cliffs. He observed that some 

of the features that Myrick (1979) had used to diagnose several 

species (overall skull size, the shape of the nasals, and the proportions of the vertex) were sufficiently variable to thwart his 

attempts to provide a morphologically discrete and consistent 

diagnosis for some of these species. Nevertheless (and possibly 

because of the limited number of specimens assigned to this species), Lambert (2004) recognized, albeit reluctantly, the validity 

of Schizodelphis barnesi. He did so not without including a cautionary reminder that although the morphology of the nasals and 

vertex seems to be sufficiently consistent to define this additional 

FIGURE 2.32. Schizodelphis barnesi. (A) USNM PAL 244403, lectotype, facial portion of the skull in dorsal view. (B) Restoration of 

the facial portion of the skull in dorsal view.
NUMBER 107 • 105

species of Schizodelphis, the five specimens that currently comprise the hypodigm might represent one extremity of the range 

of morphologies for the vertex in Schizodelphis morckhoviensis

(Lambert, 2004).

An attempt to characterize or define the statistical range of 

morphological variability that characterizes the different species 

within the Eurhinodelphinidae would be an ambitious, but instructive, endeavor. Furthermore, the discovery and description 

of the skull of a neonate would offer insights into how the proportions of the skull, especially the disparity in length between 

upper and lower mandibles, changed during ontogeny. Isotopic 

analyses of eurhinodelphinid teeth might indicate the kind of 

aquatic habitat they preferred, marine, estuarine, or fresh water 

(see Barrick et al., 1992, for an early attempt based on oxygen 

stable isotopes).

Infraorder Delphinida Muizon, 1984

Remarks on the Family Kentriodontidae.

Enthusiasts who have read about Miocene odontocetes will 

be familiar with the family Kentriodontidae (Ichishima et al., 

1994; Dawson et al., 1996; Dawson, 2002). They were thought 

to comprise an extinct assemblage of small to medium-sized 

toothed cetaceans with a wide-ranging geographic distribution 

(Barnes, 1978). By the early twenty-first century, the family 

had come to comprise a morphologically diverse assemblage of 

late Oligocene to Miocene odontocetes (Barnes, 1978, 1985a; 

Muizon, 1984, 1988a, 1988b; Ichishima et al., 1994; Dawson, 1996a, 1996b; Bianucci, 2001; Kazár, 2005; Kazár and 

Grigorescu, 2005; Lambert et al., 2005; Kazár and Hampe, 

2014; Guo and Kohno, 2021). Unfortunately, as the number 

of species assigned to this family grew, it became increasingly 

obvious that many of its members were not united by identifiable unique characteristics (Ichishima et al., 1994; Fordyce and 

Muizon, 2001; Fordyce, 2009; Marx et al., 2016; Lambert et 

al., 2017b; Peredo et al., 2018b). However, most recently, Guo 

and Kohno (2021) concluded from their phylogenetic analysis 

that all previously identified kentriodontids did, indeed, comprise a monophyletic group, which in turn was the sister group 

of crown Delphinoidea. Recently (up until Guo and Kohno, 

2021), cladistic analyses applied to increasing numbers of representatives of the family concluded that the group was polyphyletic—with many of its members representing grades of 

homodont basal delphinidans spread out between heterodont 

odontocetes, Inioidea (South American river dolphins; Iniidae 

+ Pontoporiidae), and Delphinoidea (Phocoenidae + Monodontidae + Delphinidae; Lambert et al., 2017b; Peredo et al., 

2018b). As the content of the family and its relationships with 

extant delphinidan families keep changing from one phylogenetic analysis to the next (e.g., Post et al., 2017; Lambert et al., 

2018a; Kimura and Hasegawa, 2019; Guo and Kohno, 2021), 

we provisionally prefer keeping only the type genus Kentriodon

within the Kentriodontidae.

Historically, species assigned to this family had been variously placed into the subfamilies Kentriodontinae, Lophocetinae, and Pithanodelphininae (Barnes, 1978; Muizon, 1988c). 

However, here too, Lambert et al. (2017b) found that these subfamilies were not monophyletic, and Peredo et al. (2018b) considered all three subfamilies to be nomina dubia, so we will not 

include these taxonomic entities in this review.

Kentriodon pernix Kellogg, 1927a

FIGURES 2.33, 2.34

Kentriodon pernix – Kentriodontidae

(Illustration by Tim Scheirer)

Holotype. USNM V 8060, a nearly complete skeleton (including the skull, with the bizygomatic width estimated 

at 142 mm; mandibles; ear bones [Figure 2.33C,D]; and most of 

the postcranial skeleton), found and preserved in articulation. 

Kellogg (1927a: fig. 8-20) described and illustrated the left malleus, incus, and stapes. 

Type Locality. Approximately 2.4 km south of 

Chesapeake Beach, Calvert County, Maryland.

Horizon and Age. Quarried from the cliff face 

about 1.6 m above beach level in the greenish sandy clay of SZ 5, 

Plum Point Member of the Calvert Formation (Kellogg, 1927a). 

Late Early Miocene (Burdigalian).

Known Range along Calvert Cliffs and 

in Surrounding Area. Popes Creek Sand to SZ 14, 

Fairhaven and Plum Point Members (Aquitanian to early Serravallian) of the Calvert Formation.

Referred Material. CMM-V-246, skull, Popes 

Creek Sand, Fairhaven Member, Calvert Formation; CMMV-247, skull, Popes Creek Sand, Fairhaven Member, Calvert 

Formation; CMM-V-849, skull, SZ 14, Calvert Formation; 

USNM V 10670, paratype (Figure 2.33B), skull, SZ 3B, Calvert 

Formation (Kellogg, 1927a); USNM V 11400, atlas, SZ 10, 

Calvert Formation (Kellogg, 1927a); USNM V 21027, partial 

skull, SZ 11, Calvert Formation; USNM V 22957, periotic, 

Calvert Formation; USNM V 25005, skull (Figure 2.33A), 

axial and appendicular elements, Calvert Formation; USNM 

PAL 171069, juvenile partial skull, Calvert Formation; USNM 

PAL 171070, partial skull, SZ 12, Calvert Formation; USNM 

PAL 171077, skull, Calvert Formation (Ray, 1976); USNM 

PAL 171078, skull, anterior portion, Calvert Formation; 
FIGURE 2.33. Kentriodon pernix. (A) USNM V 25005, nearly complete skull in dorsal view. (B) Restoration of the 

skull in dorsal view based on USNM V 10670. Notice that the vertex is transversely much wider than in A. Whether 

or not this morphotype represents a new species will be left to a future determination. The difference in the vertices was 

included to draw attention to the fact that we do not yet know the range of intraspecific variability in the shape of the 

vertex. (C, D) USNM V 8060, holotype, left periotic in ventral and dorsal views, respectively. C and D whitened with 

sublimed ammonium chloride. Scale bar for C and D equals 10 mm.

106 
NUMBER 107 • 107

USNM PAL 183056, skull, Calvert Formation; USNM PAL 

187486, periotic, Calvert Formation; USNM PAL 214438, 

partial skull, SZ 14, Calvert Formation; USNM PAL 256521, 

skull and axial elements, SZ 14, Calvert Formation; USNM PAL 

317875, periotic, Calvert Formation; USNM PAL 317880, partial skull, SZ 14, Calvert Formation; USNM PAL 317900, skull 

and vertebra, Fairhaven Member, Calvert Formation; USNM 

PAL 453043, periotic, Fairhaven Member, Calvert Formation; 

USNM PAL 457211, braincase, incus, and partial lower jaw, 

Calvert Formation; and USNM PAL 526525, partial skull, SZ 5, 

Calvert Formation.

Diagnosis of Species. Diagnostic characters of 

Kentriodon pernix can be found in Kellogg (1927a) and later 

works including comparisons with other species within the genus 

Kentriodon and closely related forms (e.g., Barnes and Mitchell, 

1984; Muizon, 1988c; Ichishima, 1994; Bianucci, 2001; Whitmore and Kaltenbach, 2008; Kazár and Hampe, 2014; Peredo 

et al., 2018b).

Remarks. The genus Kentriodon Kellogg, 1927a 

was long considered typical of the Kentriodontidae, and it 

formed the basis in taxonomy for the family group name. Kentriodon pernix (Figure 2.34) is represented by several specimens, including partial skeletons, from the Calvert Formation 

of Maryland and Virginia. Kentriodon pernix is a relatively 

generalized, small, delphinid-like odontocete. Bohaska (1998) 

noted the presence of several morphotypes within Kentriodon 

pernix. We concur and suggest that a detailed review of this 

species might reveal sexual dimorphism or several closely 

related species as in the extant odontocete Stenella (Perrin, 

1975).

Closely related Middle to Late Miocene species of roughly 

similar size have been named on the basis of fossils from 

the Aurora Phosphate Mine, North Carolina (Kentriodon 

schneideri Whitmore and Kaltenbach, 2008), California (Kentriodon obscurus (Kellogg, 1931)), Germany (Kentriodon hoepfeneri Kazár and Hampe, 2014), and Japan (Kentriodon 

hobetsu Ichishima, 1994; Kentriodon nakajimai Kimura and 

Hasegawa, 2019; and Kentriodon sugawarai Guo and Kohno, 

2021).

In their phylogenetic analysis, Lambert et al. (2017b) 

found that Brevirostrodelphis (Delphinodon) dividum and 

Kentriodon pernix (in that order) comprised the two earliest 

branching delphinidans, whereas Peredo et al. (2018b) and 

Kimura and Hasegawa (2019) identified a stemward delphinidan clade, Kentriodontidae, including K. pernix, other species 

of the genus Kentriodon, and Kampholophos, Rudicetus, and 

Wimahl; later, Lambert et al. (2020) recovered only Kentriodon

and Rudicetus in that clade. Guo and Kohno (2021) recovered 

a monophyletic Kentriodontidae including all the named species previously assigned to that family. As previously stated, 

the relationships in this relatively large group of delphinidans 

are clearly in a state of flux and highly volatile in recent phylogenetic analyses.

Brevirostrodelphis gen. nov.

Type and Only Referred Species. Brevirostrodelphis dividum (True, 1912).

Etymology. The generic epithet Brevirostrodelphis is a combination of three words: brevi, which is Latin for 

“abbreviated” or “short”; rostro for “rostrum”; and delphis, 

which is “dolphin” in Greek. The new generic name highlights 

the fact that its rostrum is proportionally shorter than in other 

delphinidans.

Diagnosis of Genus. As for the only referred species.

FIGURE 2.34. Skeletal restoration and possible body outline of Kentriodon pernix in left lateral view. Body length is approximately 2 m. 

Modified from Kellogg (1927a: fig. 5).
108 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Brevirostrodelphis dividum (True, 1912), new combination

FIGURE 2.35

Brevirostrodelphis dividum – Stem Delphinidan

(Illustration by Brenna Litynski)

Kellogg (1957) noted that the teeth of Delphinodon dividum

do not closely resemble the single type tooth of the genotype of 

the genus Delphinodon, that is, Delphinodon mento (Leidy, 1869: 

pl. 30, figs. 7, 8). “The type tooth of Delphinodon mento (No. 

11228, Acad. Nat. Sci. Philadelphia) is much larger than those of 

either ‘Delphinodon’ dividum or D. leidyi (Leidy, 1869, pl. 30, fig. 

12) and presents several important peculiarities not shared by the 

smaller species. When either a skull or mandible with teeth that 

match the type tooth of Delphinodon mento is found, it is quite 

probable that it will be necessary to separate D. dividum generically from D. mento” (Kellogg, 1957:286–287). Because the type 

tooth of D. mento is the size of the teeth of Hadrodelphis and 

Macrokentriodon but differs in detail and is most likely not diagnostic at the species level, we consider D. mento a nomen dubium 

and withdraw Delphinodon dividum from the genus Delphinodon

and place it in its own new genus: Brevirostrodelphis.

Holotype. USNM V 7278, complete skull (Figure 

2.35A) with periotic (Figure 2.35C,D; bizygomatic width = 163 

mm) and postcranial skeleton.

Type Locality. Calvert Cliffs south of Chesapeake 

Beach, Calvert County, Maryland.

Horizon and Age. Fairhaven and Plum Point 

Members (SZ 3B–11) of the Calvert Formation, late Early 

Miocene (Burdigalian).

Known Range. SZ 3B–11, Fairhaven and Plum Point 

Members (Burdigalian) of the Calvert Formation.

Referred Material. CMM-V-4815, small partial 

skull, SZ 11, Calvert Formation; USNM V 21304, lower jaw, Calvert Formation; USNM V 25127, rostrum, SZ 3B, Calvert Formation; USNM PAL 171096, paratype, periotic, Calvert Formation 

(True, 1912); USNM PAL 171097, paratype, periotic, Calvert 

Formation (True, 1912); USNM PAL 171098, paratype, periotic, 

Calvert Formation (True, 1912); USNM PAL 171099, paratype, 

tympanic bulla, Calvert Formation (True, 1912); USNM PAL 

171100, paratype, tympanic bulla, Calvert Formation (True, 

1912); USNM PAL 171101, paratype, tympanic bulla, Calvert 

Formation (True, 1912); and USNM PAL 317894, periotic, Calvert Formation.

Diagnosis of Species. Diagnostic characters of 

Brevirostrodelphis dividum can be found in True (1912) and a 

series of later works on early delphinidans (e.g., Kellogg, 1927a; 

Barnes, 1978; Muizon, 1988b, 1988c; Ichishima, 1994; Lambert 

et al., 2005; Kazár and Hampe, 2014).

Remarks. On the basis of their phylogenetic analyses, Lambert et al. (2017b, 2020), Peredo et al. (2018b), 

and Kimura and Hasegawa (2019) found that B. dividum

represented the earliest diverging delphinidan, even more 

stemward than Kentriodon pernix (but see Lambert et 

al., 2018, for an alternative topology). Guo and Kohno 

(2021) recovered B. dividum in a basal position with their 

Kentriodontidae.

Hadrodelphis calvertense Kellogg, 1966

FIGURES 2.36–2.40

Hadrodelphis calvertense

(Illustration by Brenna Litynski)

Holotype. USNM V 23408, incomplete mandible 

with seven teeth.

Horizon and Age. All known specimens are from 

the Calvert Formation. As both Kellogg (1966) and Dawson 

(1996a) pointed out, the stratigraphic provenance of the holotype within the Calvert Formation is uncertain. The referred 

specimen CMM-V-11 is from the Plum Point Member of the 

Calvert Formation, SZ 14, and all other specimens for which 

information is available originate from SZ 12–14, corresponding 

to a Middle Miocene age.

Known Range. SZ 12–14 (late Langhian and early 

Serravallian), Calvert Formation.

Referred Material. CMM-V-11, skull (Figures 

2.36–2.40; bizygomatic width estimated at 255 mm) and mandibles, postcranial skeleton including nearly complete vertebral 

column, ribs, scapula, and forelimb, SZ 14, Calvert Formation; 

USNM V 25707, partial lower jaw, SZ 14, Calvert Formation; 

USNM PAL 170993, partial lower jaw, right occiput, and axial 

elements, Calvert Formation; USNM PAL 182938, lower jaw, 

and axial elements, SZ 13, Calvert Formation; and USNM PAL 

546147, partial skull, premaxilla, and axial elements, SZ 12, 

Calvert Formation. 
NUMBER 107 • 109

FIGURE 2.35. Brevirostrodelphis dividum. USNM V 7278, holotype. (A) Nearly complete skull in dorsal view. 

(B) Restoration of the skull in dorsal view. (C, D) Left periotic in ventral and dorsal views, respectively. C and D whitened 

with sublimed ammonium chloride. Scale bar for C and D equals 10 mm.
110 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.36. Hadrodelphis calvertense. CMM-V-11. (A) Skull in dorsal view. (B) Restoration of the skull in dorsal view. 

(C) Anterior tooth in lingual view. (D) Posterior tooth in lingual view. Scale bar for C and D equals 10 mm.
NUMBER 107 • 111

FIGURE 2.37. Hadrodelphis calvertense. CMM-V-11. (A, B) Right periotic in dorsal and ventral views, respectively. (C–E) Right 

tympanic bulla in medial, dorsal, and lateral views, respectively. Specimen whitened with sublimed ammonium chloride. Scale 

bars equal 10 mm.
112 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.38. Hadrodelphis calvertense. CMM-V-11, cervical vertebrae. (A–C) Atlas in anterior, posterior, and dorsal views, respectively. 

(D, E) Axis in anterior and posterior views, respectively. (F) Sixth cervical vertebra in posterior view. Its right ventral transverse process is not 

broken, just poorly developed, showing its presumed arrested development. (G) Sixth and seventh cervical vertebrae in articulation in left lateral 

view. (H) Seventh cervical vertebra in posterior view.
 113

FIGURE 2.39. Hadrodelphis calvertense. CMM-V-11, thoracic, lumbar, and caudal vertebrae. (A, B) Third thoracic 

vertebra in left lateral and anterior views, respectively. (C, D) Sixth thoracic vertebra in left lateral and anterior views, 

respectively. (E, F) Lumbar vertebra in left lateral and anterior views, respectively. (G, H) Anterior caudal vertebra in left 

lateral and anterior views, respectively. (I, J) Mid-caudal vertebra in left lateral and anterior views, respectively. (K, L) 

Peduncular caudal vertebra in left lateral and anterior views, respectively. (M, N) Distal caudal vertebra within the fluke 

in left lateral and anterior views, respectively. (O, P) Chevron in anterior and left lateral views, respectively.
114 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.40. Hadrodelphis calvertense. CMM-V-11, right scapula and forelimb elements. (A) Scapula in lateral view. (B, C) Humerus in 

posterior (postaxial) and lateral views, respectively. (D) Ulna in lateral view. (E) Radius in lateral view. (F) Right first dorsal rib in posterior view. 

(G) Right posterior dorsal rib in posterior view. Abbreviation: m. = muscle.
NUMBER 107 • 115

Diagnosis of Species. Diagnostic characters of 

Hadrodelphis calvertense can be found in Dawson (1996a).

Vertebral Column. CMM-V-11 preserves 34 vertebrae (Figures 2.38, 2.39), making it one of the most complete 

skeletons of any of the Miocene odontocetes known from the 

Chesapeake Group (followed closely by the holotype of Kentriodon pernix). The postcranial skeleton includes 7 cervicals, 11 

thoracics, 16 post-thoracics, 8 chevrons, and portions of at least 

15 ribs, the sternum, a partial scapula, 1 humerus, 1 radius, and 

1 ulna. Measurements of the vertebral centra of this specimen 

were analyzed and compared to other odontocetes by Buchholtz 

(2001). Because of its degree of preservation, CMM-V-11 is illustrated here in greater detail (Figures 2.38–2.40) than it was by 

Dawson (1996a) and Dawson and Gottfried (2002).

Cervical Vertebrae. Measurements for the cervical 

vertebrae preserved in CMM-V-11 are given in Table 2.2. There 

is no fusion between any of the cervical vertebrae (Figure 2.38), 

although the bodies of the vertebrae are anteroposteriorly compressed, but not quite to the same degree as in many extant cetaceans. The epiphyses are fully fused in all the cervical vertebrae.

The atlas and axis are the largest of the cervical vertebrae 

(Figure 2.38A–E). In an anterior view of the atlas (Figure 2.38A), 

the concave reniform-shaped cranial articular foveae angle toward each other ventrally and bracket the roughly triangularly 

shaped neural canal. The posterior articular foveae are smaller 

(Figure 2.38B) and approximate the outline of a kidney bean. 

Dorsally, the neural arch comprises a relatively thin bridge of 

bone that connects the aforementioned facets. The uppermost 

portion of the neural arch is incomplete. In a dorsal view of the 

atlas (Figure 2.38C), one very large lateral vertebral foramen 

(=foramen for first spinal nerve) perforates each side of the neural arch. The left foramen is shifted anteriorly to interrupt the anterior bridge of the neural arch (Figure 2.38C). Below these large 

foramina are multiple smaller ones that open into the body of the 

atlas. The widest part of the atlas spans the blunt ventrolateral 

transverse processes that terminate lateral to the caudal articular 

foveae. Ventral to and between these foveae is the thickened ventral tubercle (=hypapophysis). It projects posteroventrally from 

the ventral arch to underlie the anterior half of the body of the 

axis. On its posterodorsal surface is a large, gently concave facet 

(=odontoid fovea) that articulated with a reciprocal facet on the 

odontoid process on the axis (Figure 2.38D). Above each posterior articular fovea, the posterolateral margin of the neural arch 

was damaged in such a way to suggest that there might have 

been a flange-like dorsal transverse process as in the new small 

delphinidan Herbeinodelphis nancei (e.g., see Figure 2.52C) gen. 

et sp. nov. (see below).

Had the neural spine on the axis been preserved, it would 

have been the highest of the cervical vertebrae (Figure 2.38D,E); 

it was certainly the widest. A strong arc-shaped horizontal carina marks the apex of the odontoid process. Below the carina 

is the nearly circular facet that articulated with the atlas. Above 

the carina is a notochordal (or ligament) pit (Figure 2.38D). On 

either side of the odontoid process, the concave anterior articular 

facets approximate the shape of those on the posterior face of 

the atlas. Lateral to these are the oblique backward and outwardly directed robust transverse processes. A small vertebrarterial canal (Figure 2.38E) perforates the upper margin of the left 

transverse process. The postzygapophyses are nearly horizontal 

and situated at the level of the top of the neural canal. The posterior articular facet on the centrum is concave centrally. On either 

side of this ovoid facet are many small foramina that enter into 

the body of the centrum at the base of the transverse processes. 

A prominent medial carina marks the ventralmost surface of 

the centrum, on either side of which are many additional small 

foramina that occupy bilateral depressions on either side of the 

longitudinal ridge.

TABLE 2.2. Measurements (mm) of the cervical vertebrae of Hadrodelphis calvertense, CMMV-11. Abbreviations and symbols: X = not preserved or inapplicable; asterisk (*) = estimated 

measurement.

Dimension Atlas Axis 3rd 4th 5th 6th 7th

Greatest depth (vertically) 110.0 X 98.0 X X 100.5 114.0

of vertebra (tip of neural spine

to inferior face of centrum)

Length of centrum 45.5 47.0 21.5 20.0 19.5 19.5 26.0

Distance across vertebra 152* 167.0 162* X 156* 136* 155.0

between tips of transverse 

processes (parapophyses)

Distance between tip of right X X 28.0 X X 40.0 49.5

postzygapophysis and tip of 

right prezygapophysis

Minimum anteroposterior X X 11.5 9.5 13.5 10.5 13.0

diameter of neurapophysis
116 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

The remainder of the cervical vertebrae (Figure 2.38F–H) 

differ from one another mostly in the size and orientation of 

their upper and lower transverse processes. In an anterior view 

of the post-axis vertebrae, the outline of the centrum would best 

be described as subcircular. The third and fourth cervicals host 

vertebrarterial foramina that are so large that none is fully enclosed by the dorsal arm of the upper transverse process. The 

fifth and sixth (Figure 2.38F,G) cervicals differ from other cervicals in that they possess (at least on one side) greatly elongate posteroventrolaterally directed lower transverse processes 

that are widely separated from their respective upper transverse 

processes. The laterally directed upper transverse processes are 

gracile by comparison.

The upper transverse processes of the seventh cervical (Figure 2.38G,H) are laterally directed. There is no development of 

lower transverse processes. Instead, in their place, a rugose patch 

of bone presumably held the capitulum of the first rib.

Thoracic Vertebrae. Measurements for the thoracic 

vertebrae preserved in CMM-V-11 are given in Table 2.3. 

The epiphyses are not fully fused in the thoracic vertebrae, 

suggesting that this individual of Hadrodelphis calvertensis

was not fully mature (Galatius and Kinze, 2003; Moran et al., 

2015). Some of the sutures in the skull are still open, providing 

congruence in age estimation. The first eight thoracic vertebrae 

are well preserved; only a few are incomplete in the height of 

their neural spines. The outline of the centrum in the first thoracic vertebra is oval. The articular surface for the tuberculum 

of the rib is large and saddle shaped. Immediately below this 

articular facet is a conspicuous cavity that marks the ventral side 

of the diapophysis. This is the only vertebra that preserves such a 

cavity. On either side of the posterolateral margin of the centrum 

is the rugose facet that held the capitulum of the rib. The neural 

spine is bladelike, tapering distally. In cross section, the spine 

is acutely wedge shaped, with the apex of the wedge pointed 

anteriorly. In most of the thoracic vertebrae, the neural spines 

are broad—the length of the base of the spine above the level of 

the postzygapophyses approximates the length of the centrum. 

In the first through fifth thoracics, the ascending posterior face 

of the neural spine presents two shallow troughs on either side 

of a median carina.

The third and sixth thoracic vertebrae are shown in Figure 

2.39A–D. They both possess broad, nearly vertical neural spines 

and short and stout diapophyses. The facet for the corresponding rib on the diapophysis is round to subcircular in outline; 

those on the sixth are smaller than those on the third thoracic. 

The size of the zygapophyseal facets approximates the size of 

TABLE 2.3. Measurements (mm) of the thoracic vertebrae in Hadrodelphis calvertense, CMM-V-11. Abbreviations and symbols: Dash (—) = no facets for tubercula; X = broken bone; c = neural arches slightly 

compressed ventrally; n/a = not available.

Dimension 1st 2nd 3rd 4th 5th 6th 7th 8th

Greatest depth (vertically) of 144.5c 178.0 174.5 X X 200c X X

vertebra (tip of neural spine 

to inferior face of centrum)

Height of anterior face of 53.5 48.0 46.5 46.5 46.0 49.5 51.0 53.5

centrum

Breadth of centrum posteriorly 76.0 72.5 71.0 70.5 69.5 65.5 — —

across facets for capitulum

Length of centrum 37.5 44.0 48.0 51.5 55.5 58.5 63.0 67.0

Distance across vertebra 136.5 126.5 122.0 122.5 118 116.0 n/a n/a

between tips of diapophyses

Distance across vertebra n/a n/a n/a n/a n/a n/a 114.0 X

between tips of transverse 

processes (parapophyses)

Minimum length of

neurapophysis 19.5 15.5 17.0 19.0 20.0 22.0 24.5 31.0

Vertical height of neural spine 53c 90.0 85.0 X X 118c X X

(distance between superior

margin of neural canal and

tip of spine)

Minimum anteroposterior 18.0 26.0 28.5 X X X X X

 diameter of the neural spine
NUMBER 107 • 117

the facets on the diapophyses. The eighth thoracic vertebra presents a parapophysis (transverse process) that articulated with a 

single-headed rib.

One lumbar vertebra is illustrated here (Figure 2.39E,F). It 

appears to be nearly complete vertically; its overall height is approximately 175 mm. Its centrum is deeper (centrum height = 62 

mm) and longer (>87 mm) than previously referenced thoracics. 

Furthermore, its neural canal is approximately triangular in anterior outline (Figure 2.39E,F), and its prezygapophyses are bilaterally compressed and positioned above the neural canal. The 

entire neural arch and spine are shifted more anteriorly on the 

centrum compared to previously described thoracic vertebrae. 

Its neural spine is bladelike both anteriorly and posteriorly. It 

exhibits wide ventrolaterally sloping transverse processes. The 

width across these transverse processes is 224 mm.

Caudal Vertebrae. Four caudal vertebrae of 

CMM-V-11 are shown in Figure 2.39G–N, and in all of these, 

the epiphyses are fully fused. Their centra are enlarged relative to the previously described centra of thoracic vertebrae. 

Figure 2.39G,H shows one of these. Its overall height is at least 

194 mm. As in the aforementioned illustrated lumbar vertebra, 

the neural arch and spine of this anterior caudal vertebra are 

shifted toward the anterior end of the centrum. The height of 

the anterior face of its centrum is 81 mm. The root of the transverse process extends for most of the length of the centrum. 

The overall width of the vertebra across its transverse processes 

is 228 mm. A single spinal arterial canal/foramen passes dorsoventrally through the root of the base of the right transverse 

process. “Teardrop” describes the shape of its neural canal as 

seen in anterior view (Figure 2.39H). Ventrally, it presents four 

hemal facets, the enlarged posterior two of which are triangular 

in ventral view, each enclosing a central pit.

Figure 2.39I,J shows another more distal vertebra, one 

of the peduncular caudal vertebrae. It is identified as peduncular because its neural spine and transverse processes are 

greatly reduced. Its overall height is 148 mm, and the height 

of the anterior face of its centrum is 80 mm. Its neural canal 

is between 5 and 7 mm wide. Just posterior to the midpoint 

in the length of the centrum, bilateral arterial foramina are 

seen below and adjacent to the neural arch and pass vertically 

through the body of the centrum. Ventrally, each foramen 

opens on the ventrolateral side of the centrum and penetrates 

the longitudinal ridge created by the hemal processes. Figure 

2.39K,L shows the last peduncular vertebra. It is without a 

neural spine or transverse processes. Its circular anterior face 

is 63 mm in diameter. The length of the centrum is 44 mm, 

so this vertebra is higher and wider than it is long. There is a 

cluster of vertebrarterial foramina that variously pass vertically through the centrum.

CMM-V-11 preserves four distal caudals that would have 

been within the fluke. They are all wider than they are high, 

a characteristic of vertebrae within the fluke (Buchholtz, 

2001; Uhen, 2004). The second of these is illustrated in Figure 

2.39M,N. Buchholtz (2001) reported that Hadrodelphis has a 

pattern 2 vertebral anatomy, which indicates greater flexibility in 

the anterior than posterior torso, an adaptation that also characterized eurhinodelphinids. This vertebral pattern allows the fluke 

to oscillate on an elongate stabilized peduncle. Furthermore, the 

anterior torso retains more mobile elongate vertebrae; this swimming pattern is also characteristic of the living Amazon river dolphin Inia geoffrensis (Buchholtz, 2001).

One chevron is included in Figure 2.39O,P. In anterior view, 

it is Y shaped, whereas in left lateral view (Figure 2.39P), it 

presents wedge-shaped facets dorsally that articulated with the 

hemal processes and a wide strap of bone ventrally.

Ribs. Parts of at least 15 ribs are preserved in CMM-V11 (Figure 2.40F,G). Judging from its size and shape, the rib in 

Figure 2.40F represents the first right rib. Its maximum straightline length is 309 mm. This rib is wide and flattened throughout 

its length. The poorly defined face of the capitulum is not borne 

on a short, thick neck. The tuberculum is larger than the capitulum. Beyond the tuberculum, the shaft turns at right angles. 

Distally, the shaft continues to curve gently medially. The distal 

end of the rib thickens anteroposteriorly for attachment of the 

sternal rib.

Figure 2.40G is a single-headed rib that would have articulated with the transverse process of the eighth or succeeding thoracic vertebra. Its maximum straight-line length is 433 mm. At 

about the midpoint in its length, it shows callus formation, evidence of healing of a prior fracture (see Dawson and Gottfried, 

2002, for more details).

CMM-V-11 also preserves the manubrium and second 

sternal element, preserved as two large subrectangular platelike 

bones. The manubrium includes strong anterodorsolaterally projecting prongs of bone that would have articulated with the first 

rib. The second element also preserves articulation for sternal 

ribs.

Dawson (1996a) adequately described those elements of the 

forelimb (right humerus, radius, and ulna) of Hadrodelphis that 

are preserved in CMM-V-11 (Figure 2.40A–E).

Remarks. Kellogg (1966) did not assign this species to 

any family of odontocete; the holotype is only part of a mandible with some teeth. When the more complete specimen, CMM 

V-11, became available, Dawson (1996a:125) assigned it to the 

family Kentriodontidae and to the subfamily Lophocetinae (but 

see comments above on the current status of these groups; Kentriodontidae is either paraphyletic or includes a smaller number 

of species, and Lophocetinae has not been recovered in recent 

phylogenies; Lambert et al., 2017b, 2020; Peredo et al., 2018b; 

Kimura and Hasegawa, 2019). In more recent works, H. calvertensis has been recovered either as a stem delphinidan or a stem 

delphinoid. Guo and Kohno (2021) found that H. calvertensis

was sister to Tagicetus joneti, both of which were coupled with 

Macrokentriodon morani.
118 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Macrokentriodon morani Dawson, 1996b

FIGURES 2.41, 2.42

Macrokentriodon morani

(Illustration by Brenna Litynski)

Holotype. CMM-V-15, skull (Figures 2.41A, 

2.42C,D; bizygomatic width greater than 290 mm) with 12 associated teeth and the right periotic. 

Type Locality. Approximately 0.32 km south of 

Camp Conoy Road, north of Rocky Point, Moran’s Beach, Calvert County, Maryland.

Horizon and Age. Found at the contact between 

the Drumcliff Member (SZ 17) and the St. Leonard Member (SZ 

18) of the Choptank Formation, Chesapeake Group, late Middle 

Miocene (Serravallian).

Known Range. SZ 14–18 (Serravallian), Calvert and 

Choptank Formations.

Referred Material. USNM V 11977, partial 

skull (Figure 2.42A,B), SZ 14, Calvert Formation; USNM PAL 

299694, skull, Calvert Formation; and USNM PAL 517874, 

partial skull (postorbital width estimated at 276 mm) including 

the rostrum, the facial area, and the right part of the vertex, 

Choptank or St. Marys Formation.

Diagnosis of Species. Diagnostic characters of 

Macrokentriodon morani can be found in Dawson (1996b).

Remarks. Lambert et al. (2017b) found that Macrokentriodon and Hadrodelphis, with Kampholophos serrulus, formed a clade of stem delphinidans branching after 

Brevirostrodelphis dividum and Kentriodon pernix, a topology similar to that recovered by Post et al. (2017), Peredo 

et al. (2018b), Kimura and Hasegawa (2019), and Lambert 

et al. (2020), whereas all these taxa are identified as stem 

delphinoids in Lambert et al. (2018a). Guo and Kohno 

(2021) recovered Macrokentriodon deeply nested within the 

Kentriodontidae.

Miminiacetus gen. nov.

Type and Only Referred Species. Miminiacetus pappus (Kellogg, 1955), new combination.

Etymology. The generic epithet Miminiacetus is a 

combination of three words: mimicus, which is Latin for “imitative,” referring to a mimic; the generic name Inia for the South 

American freshwater boto or Amazon river dolphin; and ketos, 

Greek for a large sea animal or whale, here using the Latin form 

of the noun, cetus. The reference to Inia reflects the proportional 

similarities of the skull of this species with that of Inia geoffrensis

(Blainville, 1817), the Amazon river dolphin. Such similarities 

were pointed out in the original description and comparisons by 

Kellogg (1955:101), and they led him to imply that this species 

belonged in the family Iniidae.

Diagnosis of Genus. As for the only referred species.

Miminiacetus pappus (Kellogg, 1955), new combination

FIGURES 2.43, 2.44

Miminiacetus pappus

(Illustration by Tim Scheirer)

The odontocete cetacean Lophocetus pappus Kellogg, 1955 

was based on USNM V 15985, a skull, periotic, and mandible 

from the Middle Miocene part of the Calvert Formation in Calvert County, Maryland. Kellogg originally allied (but did not 

specifically assign) this species to the family Iniidae. The genus 

Lophocetus Cope, 1868 previously included only its type species, Lophocetus calvertensis (Harlan, 1842), which, at the time 

of Cope, was known only by its holotype, a partial skull with a 

periotic (see below).

Barnes (1978) concluded that the holotype skull of Lophocetus pappus differed sufficiently from the holotype skull of 

Lophocetus calvertensis that the two species do not belong in the 

same genus. Barnes noted that the holotype periotic of L. pappus is sufficiently similar to those of Liolithax kernensis Kellogg, 

1931, a fossil species from the eastern North Pacific, that the two 

might be congeneric. Thus, he transferred Lophocetus pappus to 

the genus Liolithax Kellogg, 1931 and reidentified the species 

not as an iniid, but as a kentriodontid. On the basis of similarities between the periotics of Liolithax kernensis, Lophocetus

pappus, and the holotype of the Middle Miocene Kampholophos

serrulus Rensberger, 1969 from northern California, Barnes classified these odontocetes in the kentriodontid subfamily Kampholophinae, which has as its type genus Kampholophos.

Kellogg (1931) had based Liolithax kernensis on isolated 

periotics from the Middle Miocene Sharktooth Hill Bone Bed 

in central California. Subsequently, several more isolated 

periotics of this species have been recovered from the same 

bone bed, but no skull with an associated periotic of Liolithax
NUMBER 107 • 119

FIGURE 2.41. Macrokentriodon morani. CMM-V-15, holotype. (A) Skull in dorsal view. (B) Restoration of the skull 

in dorsal view.
FIGURE 2.42. Macrokentriodon morani. (A, B) USNM V 11977, skull in posterior and ventral views, respectively. (C, D) 

CMM-V-15, holotype right periotic in dorsal and ventral views, respectively. C and D whitened with sublimed ammonium 

chloride. Scale bar for C and D equals 10 mm.

12 0 
NUMBER 107 • 121

kernensis has ever been collected from that deposit. Thus, 

the affinities of Liolithax kernensis have, for many years, remained uncertain.

Subsequently, a specimen was obtained from the Middle 

Miocene Rosarito Beach Formation near La Misión in northern 

Baja California, Mexico (Flores-Trujillo et al., 2000). This new 

specimen includes the uncontrovertibly associated skull, mandible, and periotic. The periotic of this specimen from Mexico 

indicates that it is congeneric, but not conspecific, with Liolithax 

kernensis, and it represents a new species of Liolithax. The skull 

of this specimen indicates that northeastern Pacific Liolithax is 

very different from L. pappus. Thus, the specimen from Mexico 

demonstrates that contrary to the earlier conclusions of Barnes 

(1978), “Lophocetus” pappus, in addition to not being correctly 

assigned to the genus Lophocetus, is also not correctly assigned 

to the genus Liolithax. Accordingly, a new generic name is provided for “Lophocetus” pappus.

Holotype. USNM V 15985 (Figure 2.43A,D,E), 

skull (bizygomatic width estimated at 254 mm), periotic (Figure 

2.44A,B), mandible, 75 teeth, left periotic, right tympanic bulla, 

atlas and 3 other cervical vertebrae, 4 thoracic vertebrae, and 

parts of 10 ribs. 

Type Locality. According to Kellogg (1955), the holotype specimen USNM V 15985 was collected in 1939 “approximately nine-tenths of a mile [1.4 km] north of mouth of Parker 

Creek [today now Parkers Creek],” in Calvert County, Maryland.

Horizon and Age. The holotype is from the Calvert 

Formation, SZ 11 of the Chesapeake Group, approximately 30 

cm below the contact with the overlying SZ 12, early Middle 

Miocene (Langhian). The original referred specimen, USNM V 

20659, is from a location stratigraphically higher, from the Calvert Formation, SZ 14, approximately 90 cm above the contact 

with the underlying SZ 13, Middle Miocene.

Known Range. SZ 11–14 (Langhian and early Serravallian), Calvert Formation.

Referred Material. CMM-V-3780 (Figure 2.43B), 

skull, SZ 12, Calvert Formation; CMM-V-4655, nearly complete skull (Figure 2.44C,D), SZ 14, Calvert Formation; USNM 

V 20659 (paratype; Kellogg, 1955), cranial elements, rostrum, 

right periotic, appendicular element, left scapula, and axial 

elements, SZ 14, Calvert Formation; and USNM PAL 360030, 

anterior right lower jaw, Calvert Formation.

Emended Diagnosis of Species. An early delphinidan that can be diagnosed on the following unique combination of 

characters: the width of the skull across the supraorbital processes 

is 60% of the length of the rostrum; rostrum relatively thick dorsoventrally and parallel sided anteriorly with a wide distal extremity; 

in dorsal view, right premaxilla wider than left along the posterior 

half of the rostrum; skull with a narrow facial region, with the margin of the frontals and maxillae over the temporal fossae constricted 

posteriorly, resulting in wide exposure of the squamosals in dorsal 

view; the premaxillary sac fossae elevated above the surrounding 

bone and curving strongly around the anterolateral corners of the 

bony nares; premaxillary sac fossae slightly concave along their 

anteroposterior axis; premaxillae form the posterolateral corners 

of the bony nares; posterolateral and the dorsalmost corner of the 

premaxilla forms a small, ziphiid-like, lateral projection (premaxillary crest); posterodorsal extremity of the premaxillae rises to the 

same level of the cranial vertex; nasal bones and frontal bones at 

the cranial vertex more constricted medially between the posterior 

ends of the maxillae; in a lateral view, the nasals and frontals form a 

horizontally flattened and relatively elongate cranial vertex; in dorsal view, a pronounced concavity is present between the nasals; low 

cranial vertex only slightly elevated above the level of the rostrum; 

well-developed and prominent posteriorly projecting temporal 

crests, which form the posteriormost part of the skull; periotic with 

a more sinuous outline, a flatter cerebral surface, a relatively smaller 

cochlear portion, a longer and larger anterior process, and a less 

circular internal acoustic meatus; 25–27 teeth per dental quadrant 

for a total of just over 100 teeth; and symphysis of the lower jaw 

just slightly longer than half the length of the mandibular tooth row.

Remarks. Kellogg (1955:101) implied but did not 

specifically state that Miminiacetus pappus belonged in the family Iniidae. Rensberger (1969), in his study of Kampholophos, 

assigned both genera to the family Iniidae. Barnes (1978) and 

Ichishima et al. (1994) placed both Kampholophos serrulus and 

M. pappus (in those studies referred to as Liolithax pappus) in 

the subfamily Kampholophinae and Lophocetus in the subfamily 

Lophocetinae, and they placed both of these subfamilies within 

the Kentriodontidae.

Lambert et al. (2017b), Peredo et al. (2018b), and Kimura 

and Hasegawa (2019) recovered Miminiacetus pappus as sister 

group to Lipotidae, a relationship that may help improve our 

understanding of the morphology of extinct members (like the 

hyper-longirostrine Parapontoporia) of this poorly known lineage that gave rise to the recently extinct Yangtze river dolphin 

(Lipotes vexillifer). However, a different topology was found in 

other recent analyses, with M. pappus being more closely related 

to the other robust forms Kampholophos, Macrokentriodon, 

and Hadrodelphis, either as stem delphinidans or as stem delphinoids (Post et al., 2017; Lambert et al., 2018a, 2020). Guo and 

Kohno (2021) recovered M. pappus basal to the Pithanodelphis

+ Lophocetus + Atocetus clade.

Pithanodelphis cornutus (du Bus, 1872)

FIGURE 2.45

Lectotype. IRSNB M.373-3652, partial skull (bizygomatic width estimated at 134 mm) including the right orbit, 

bony nares, vertex, and right part of the basicranium (illustrated 

in Abel, 1905: figs. 24, 25; Muizon, 1988b: fig. 101).

Type Locality. No precise locality, Antwerp area, 

Belgium.

Horizon and Age. No precise data available. Considering the age of the referred specimen from the Calvert Formation 

(see below), an origin of the lectotype in Middle Miocene levels of 

the Antwerpen Sands Member of the Berchem Formation is likely.
12 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.43. Miminiacetus pappus. (A) USNM V 15985, holotype, skull in dorsal view. (B) CMM-V-3780, 

nearly complete skull in dorsal view. (C) Restoration of the skull in dorsal view. (D) USNM V 15985, holotype, 

rostrum in ventral view showing wear facets on maxillary teeth. (E) USNM V 15985, holotype, anteriormost 

upper left tooth in lingual view showing semicircular wear facet.
NUMBER 107 • 12 3

FIGURE 2.44. Miminiacetus pappus. (A, B) USNM V 15985, holotype, left periotic in ventral and dorsal views, respectively. (C, D) CMM-V-4655 in dorsal and ventral views, respectively; largest skull of M. pappus currently known. 

A and B whitened with sublimed ammonium chloride. Scale bar for A and B equals 10 mm.
12 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Known Range along Calvert Cliffs. SZ 14, 

Plum Point Member (Serravallian) of the Calvert Formation. The 

specimen USNM PAL 187575 is the only one with precise locality and stratigraphic data because no such information is available for the Belgian lectotype (du Bus, 1872; Abel, 1905).

Referred Material. CMM-V-11306, partial 

skull, occipital region; and USNM PAL 187575 (Figure 2.45), 

partial skull (bizygomatic width estimated at 144 mm), consisting of the facial region across the supraorbital processes 

of the frontals and forward from the lacrimal back to include 

the vertex and the dorsal part of the supraoccipital, and part 

of the basicranium, including the vomer, basisphenoid, basioccipital, part of the alisphenoids, and the left squamosal. 

The specimen was collected from Colony Cliffs, about 7.5 

cm above the beach, 548 m north of Cat Creek, St. Mary’s 

County, Maryland. Emese Kazár (as indicated on a label associated with the USNM specimen) first recognized the affinities 

of the specimen USNM PAL 187575 with the Belgian lectotype of Pithanodelphis cornutus.

Emended Diagnosis of Species. This small Kentriodon pernix–size odontocete can be diagnosed on the basis 

of the following unique combination of characters: bizygomatic 

width ranging from 134 to 144 mm (but neither of the two currently known specimens corresponds to a fully mature individual); roughly symmetrical cranial vertex; inflated nasals elevated 

above other bones contributing to the vertex; exposure of each 

nasal on the vertex approximately as wide as it is long; internasal fossa moderately to deeply excavated; vertex conspicuously 

shortened anteroposteriorly; nasals contact or nearly contact the 

supraoccipital on either side of the frontals on the occipital face 

of the skull; maxilla-frontal contact either highly reduced or absent superficially on the vertex; and small wedge-shaped frontals 

exposed on the vertex only between the nasals.

Pithanodelphis cornutus further differs from Sophianaecetus 

commenticius (Kazár, 2005, 2006) in that in the latter form, the 

nasals abut only anteriorly, they are not inflated, they are flat on 

top, and they exhibit only a faint anterolateral notch, whereas in 

the former, the nasals abut for almost half their length, they are 

inflated, they are convex dorsally, and they exhibit a prominent 

anterolateral notch. Unlike P. cornutus, S. commenticius does 

not appear to possess a posterior dorsal infraorbital foramen. In 

both P. cornutus and S. commenticius, the posterior margin of 

the maxilla is in direct contact with the supraoccipital.

Pithanodelphis cornutus differs from Atocetus iquensis and 

A. nasalis in that its nasals are not as inflated, the anterior margin of each nasal is cut by a deep vertical notch, its nasals contact 

or nearly contact the supraoccipital (in Atocetus spp. they remain distant), and the frontals gain more exposure (even more in 

the referred specimen) between the nasals on the vertex (in Atocetus spp. they only sliver their way between the nasals but also 

preclude the nasals from making contact with the supraoccipital; 

for a detailed comparison of Atocetus spp. with the lectotype of 

P. cornutus, see Barnes, 1985a; Muizon, 1988b).

Description of the Referred Specimen. On 

the basis of the bizygomatic width estimates (144 versus 134 

mm), USNM PAL 187575 is larger than the lectotype, a difference that could be at least partly related to a different ontogenetic stage (the type specimen is from a younger individual, with 

cranial sutures more widely open).

Premaxilla. The premaxillae are preserved only from 

the point immediately posterior to the premaxillary foramen 

(roughly at the level of the antorbital notch) back to the vertex. 

Anteromedially they abut, roofing over the mesorostral canal 

at least in that area. Posteriorly, they present wide, dorsoventrally thickened, and concave premaxillary sac fossae. A shallow 

trough leading from the premaxillary foramen indicates the presence of a short posterolateral sulcus; however, much of the bone 

surface is eroded, so its actual posterior extent is unknown. Posterolaterally, the posterolateral plate of the premaxilla extends 

lateral to the medial plate of the maxilla for a short distance (best 

seen in posterodorsal view). At the level of the posterior margin 

of the bony nares, the premaxilla is slightly laterally thickened. 

There is broad contact between the premaxillae and the nasals 

adjacent to the vertex and no contact between the premaxillae 

and frontals.

Maxilla. The dorsal surface of each maxilla preserves 

a single relatively large dorsal infraorbital foramen just slightly 

posterolateral to the position of the premaxillary foramen. 

Above the orbit, the lateral margin of the maxilla is slightly concave medially. Posterior dorsal infraorbital foramina lie adjacent 

to the nares: one on the left and two on the right. In the type, 

a second, tiny posterior dorsal infraorbital foramen is similarly 

observed on the left side. Posteromedially, the maxillae suture to 

the supraoccipital, precluding any dorsal exposure of the frontals along the nuchal crest. There is no superficial maxilla-frontal 

contact on the vertex, whereas in the type, each maxilla is separated from the posterolateral corner of the corresponding frontal 

only because sutures are widely open in this area.

Nasal. The anterior face of each nasal is deeply notched 

by a vertical indentation immediately medial to the nasal-premaxilla suture, as in many other early delphinidans. The maximum width of each nasal is located anteriorly, with the lateral 

margins of both nasals converging markedly posteromedially, 

each nasal being subtriangular in outline. The nasals are inflated, 

comprising the majority of the vertex, including its highest point. 

Although the left nasal is more elevated than the right one, this 

is simply a preservational artifact, the result of breakage below 

the left nasal and its displacement dorsally. In anterior view, a 

depression between the most inflated lateral parts of the two nasals corresponds to a moderately deep internasal fossa, shallower 

than in the type. The most unusual feature exhibited by USNM 

PAL 187575 is the nasal-supraoccipital contact posteriorly, precluding the frontals from contacting the maxillae superficially 

adjacent to the vertex. This feature is unique among the Odontoceti and, as mentioned above, slightly more advanced in USNM 

PAL 187575 than in the type.
 12 5

FIGURE 2.45. Pithanodelphis cornutus. USNM PAL 187575. (A) Facial region of the skull in dorsal view. (B) Interpretive 

drawing of A. (C) Posterodorsal view. (D) Right lateral view. (E) Anterior view. (F) Right lateral view of the right zygomatic 

process of the squamosal. (G) Basicranium in dorsal (internal) view. Specimen whitened with sublimed ammonium chloride.
12 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Frontal. The supraorbital margin of the frontal 

is thickened dorsoventrally, and in dorsal view, it is slightly 

concave medially, as in the type, paralleling the supraorbital 

margin of the maxilla (Figure 2.45). The preorbital process 

is moderately thickened, and the vertical postorbital process 

is most likely incomplete (better preserved as a slender, vertical process in the type). Ventrally, the supraorbital process is 

excavated by a fossa for the postorbital lobe of the pterygoid 

sinus, which is restricted to the medial region. A similar fossa 

is observed in the type, associated with a large fossa for the 

preorbital lobe extending posterolaterally to the infratemporal 

crest. On the vertex, the frontals are greatly reduced to two 

small forward-facing wedge-shaped straps of bone between 

the swollen nasals (Figure 2.45B). The reduced exposure of the 

frontals on the vertex is even narrower (maximum width equals 

7.5 mm) in the type.

Supraoccipital. The supraoccipital sends an anteromedial projection between the maxillae, which is wider than in 

the type and, as mentioned previously, contacts the posterior tip 

of the nasal.

Lacrimal. The dorsoventrally thickened left lacrimal 

(more so than the preorbital process of the frontal) is well preserved in USNM PAL 187575 and forms the rounded anterolateral border of the antorbital notch. Considering that part of the 

medial margin of the lacrimal is parallel to the long axis of the 

skull, the antorbital notch was originally barely open anterolaterally. In dorsal view, the overlapping left maxilla is not completely preserved, showing the diagonal lacrimal-frontal suture 

(Figure 2.45A,B).

Squamosal. The squamosal is better preserved in the 

type, with a characteristic subrectangular outline of the zygomatic process in lateral view and a short postglenoid process. In 

USNM PAL 187575, the mandibular fossa is similarly narrow, 

excavated medially by a deep tympanosquamosal recess whose 

surface is hollowed by multiple small pits.

Remarks. In addition to this more precise geological age and expansion of the paleogeographic distribution (the 

species is now recorded from both sides of the North Atlantic), 

USNM PAL 187575 provides further information about the facial region of the skull and intraspecific variation (at least partly 

related to ontogeny) for this poorly known species.

Within Mio-Pliocene delphinidans, Pithanodelphis cornutus most closely resembles Atocetus spp., Leptodelphis stavropolitanus, and Sophianaecetus commenticius (previously named

Mediocris commenticus), which are usually placed within the 

subfamily Pithanodelphininae (see Barnes, 1985a; Muizon, 

1988b, 1988c; Kazár, 2005). Three recent phylogenetic analyses recovered P. cornutus in a clade of crown delphinidans diverging between Lipotidae and Inioidea, together with Tagicetus 

joneti and species of Atocetus and Lophocetus (Lambert et al., 

2017b; Peredo et al., 2018b; Kimura and Hasegawa, 2019). The 

discovery of more complete specimens of this very rare species, 

including the periotic, may potentially strengthen the support for 

this clade, ultimately leading to the resurrection of the Pithanodelphininae. Guo and Kohno (2021) recently recovered Pithanodelphis as closely related to Miminiacetus, Lophocetus, and 

Atocetus.

Having come from the early Middle Miocene Plum Point 

Member (SZ 14) of the Calvert Formation, P. cornutus is approximately 14–15 million years old (Serravallian), older than 

its possible relatives for which age is confidently known: Atocetus spp., Tortonian of California and Peru (Barnes, 1985a; 

Muizon, 1988b; Di Celma et al., 2017); Leptodelphis stavropolitanus, Sarmatian (Tortonian) of Stavropol, Russian Federation (Kirpichnikov, 1954); Lophocetus spp., Tortonian of 

Calvert Cliffs and California (see below; Barnes, 1978); Sophianaecetus commenticius, Serravallian of Hungary (Kazár, 

2005); and Tagicetus joneti, late Serravallian of Portugal (Lambert Et Al., 2005).

Lophocetus calvertensis (Harlan, 1842)

FIGURES 2.46, 2.47

Lophocetus calvertensis was the first odontocete to be 

named from Calvert Cliffs (Harlan, 1842, as Delphinus calvertensis) and among the first North American fossil vertebrates 

to receive a Linnean binomial (Simpson, 1942; Gottfried et al., 

1994). Lophocetus calvertensis is known only from three incomplete skulls (the first two of which were found about 150 years 

apart but in the same geographic area).

Holotype. USNM V 16314 (Figures 2.46A,B,D, 

2.47), incomplete skull lacking both zygomatic processes, supraorbital processes, and distal end of rostrum; associated with the 

right and left periotics, first through seventh cervical vertebrae, 

and first and second thoracic vertebrae. 

Type Locality. Calvert Cliffs, Cove Point, Calvert 

County, Maryland (Harlan, 1842; Barnes, 1978).

Horizon and Age. St. Marys Formation (Barnes, 1978), 

Tortonian.

Known Range. SZ 22–23, Little Cove Point Member 

(Tortonian) of the St. Marys Formation.

Referred Material. CMM-V-4062, partial vertex 

(Figure 2.46C); and CMM-V-9822, partial skull. CMM-V-4062 

and CMM-V-9822 were found in the Little Cove Point Member 

(SZ 22–23) of the St. Marys Formation, Tortonian, early Late 

Miocene, 10–9 Ma.

Emended Diagnosis of Species. An early delphinidan that can be diagnosed on the basis of the following unique 

combination of characters: medial margins of premaxillae on 

rostrum depressed adjacent to mesorostral canal; medial parts 

of premaxillae anterior to bony nares and between antorbital 

notches depressed relative to lateral parts of premaxillae; having skull with posterior parts of nasal bones and frontals much 
NUMBER 107 • 127

FIGURE 2.46. Lophocetus calvertensis. (A) USNM V 16314, holotype, skull in dorsal view. (B) Outline of cranial elements as preserved in A. (C) CMM-V-4062, partial vertex of skull in dorsal view. (D) USNM V 16314, 

holotype skull in left lateral view. Specimens whitened with sublimed ammonium chloride.
12 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

constricted on the cranial vertex by right and left maxillae, which 

encroach toward midline of skull; anterior surfaces of nasals bulbous and protruding anteriorly toward bony nares; nasals cleft 

by median sulcus; and wedge of supraoccipital bone extending 

into cranial vertex between dorsal exposure of frontal bones.

Remarks. In their phylogenetic analyses, Lambert et 

al. (2017b), Peredo et al. (2018b), and Kimura and Hasegawa 

(2019) found that L. calvertensis falls in a branching clade between lipotids and inioids, whereas a sister-group relationship 

with Atocetus spp. among stem delphinoids was found in another analysis (Lambert et al., 2018a). More recently, Guo and 

Kohno (2021) recovered L. calvertensis nested between Pithanodelphis and Atocetus.

Herbeinodelphis gen. nov.

FIGURES 2.48–2.54

A new small odontocete was found in SZ 13 of the Calvert 

Formation and is assigned to a new genus and species.

Type and Only Included Species. Herbeinodelphis nancei.

Etymology. The generic epithet Herbeinodelphis

honors Hillary Murdoch, from “Herbein,” the maiden name of 

Hillary, the spouse of Paul R. Murdoch, who found the holotype 

skull. “Herbein” means one that plays the harp (a serendipitous allusion to the mythical sirens of old), and delphis is Greek 

for dolphin. The “o” in Herbeinodelphis was added for ease of 

articulation.

Diagnosis of Genus. As for the type and only species.

Herbeinodelphis nancei sp. nov.

Holotype. CMM-V-8343, a partial skull consisting 

of a complete rostrum (preserving four teeth in situ) back to 

the level of the right supraorbital process (Figure 2.48), the 

right periotic (Figure 49), the right bulla (Figure 2.50), approximately two-thirds of the lower jaw with 12 teeth in situ 

(Figure 2.51), all cervical vertebrae (Figure 2.52), thoracic 

vertebrae 1–10 (Figure 2.53), one peduncular caudal vertebra 

(Figure 2.53), one distal caudal vertebra (Figure 2.53), and 

five ribs (Figure 2.54). 

The skull of CMM-V-8343 is thought to have been complete when its occiput began to be exposed through natural erosion on the cliff face. Unfortunately, by the time permission was 

obtained to quarry the specimen, the neurocranium had been 

severely vandalized.

Type Locality. Southern end of Warriors’ Rest Sanctuary, Calvert Cliffs, Calvert County, Maryland.

Horizon and Age. SZ 13, Plum Point Member, 

Calvert Formation.

Known Range. SZ 13, Plum Point Member (early 

Serravallian) of the Calvert Formation.

Etymology. The specific epithet nancei recognizes 

CMM paleontology collections manager John R. Nance for his 

work in preparing the type specimen and for his many years as a 

gifted fossil finder in service to the science of paleontology. Nancei was created in accordance with Article 31.1.2 of the ICZN by 

adding an “i” to “Nance.”

FIGURE 2.47. Lophocetus calvertensis. (A, B) USNM V 16314, holotype, left periotic in ventral and dorsal views, respectively. Specimen 

whitened with sublimed ammonium chloride. Scale bar equals 10 mm.
NUMBER 107 • 12 9

FIGURE 2.48. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype. (A–C) Partial skull in dorsal, right lateral, and ventral 

views, respectively. (D) Three in situ left maxillary teeth (at about mid-length of the tooth row) in medial view. Partial skull whitened with 

sublimed ammonium chloride.
130 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.49. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype, right periotic. (A) Ventral view. (B) Medial 

view. (C) Dorsal view. (D) Lateral view. (E) Oblique dorsal view into the internal acoustic meatus. The periotic was whitened 

with sublimed ammonium chloride. Scale bar equals 10 mm.
NUMBER 107 • 131

FIGURE 2.50. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype, right tympanic bulla. (A) Dorsal view. 

(B) Lateral view. (C) Ventral view. (D) Medial view. The bulla was whitened with sublimed ammonium chloride. Scale bar 

equals 10 mm.
132 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY 

FIGURE 2.51. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype, 

mandible. (A) Dorsal view. (B) Left lateral view.
 133

FIGURE 2.52. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype, cervical vertebrae. (A–C) Atlas in anterior, left 

lateral, and posterior views, respectively. (D–F) Axis in anterior, left lateral, and posterior views, respectively. (G) Third cervical 

vertebra in anterior view. (H) Fourth cervical vertebra in anterior view. (I) Fifth cervical vertebra in anterior view. (J, K) Sixth 

cervical vertebra in anterior and left lateral views, respectively. (L) Seventh cervical vertebra in anterior view.
134 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.53. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype, thoracic and caudal vertebrae. 

(A) First thoracic vertebra in anterior view. (B) Third thoracic vertebra in anterior view. (C) Fifth thoracic vertebra in 

anterior view. (D) Sixth thoracic vertebra in anterior view. (E) Seventh thoracic vertebra in anterior view. (F) Thoracic 

vertebrae 1–8 in left lateral view. (G, H) Peduncular caudal vertebra in anterior and left lateral views, respectively. 

(I) Distal caudal vertebra in anterior view.
NUMBER 107 • 135

FIGURE 2.54. Herbeinodelphis nancei gen. et sp. nov. CMM-V-8343, holotype, ribs in posterior view. (A) Right first rib. 

(B) Left second or third rib (reflected). (C) Left third, fourth, or fifth rib (reflected). (D) Right fourth, fifth, or sixth rib. 

(E) Right seventh or further posterior rib.
136 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Referred Material. None at this time.

Diagnosis of Species. Small (Pontoporia blainvillei–size) odontocete with estimated condylobasal length of 400 

mm that can be diagnosed on the basis of the following unique 

combination of characters: narrow elongate rostrum with ratio 

of length/width at base equal to 3.25; rostrum length 273 mm 

(antorbital notch to anterior extremity); 55 alveoli in left maxilla; 

2 (possibly 3) alveoli per premaxilla; dorsal exposure of maxilla at rostrum base not significantly wider than premaxilla; 

anterodorsal corner of the zygomatic process of the squamosal 

anterior to anteroventral corner; tympanosquamosal recess occupying less than one-third of the height of the anterior part 

of the zygomatic process; markedly anteriorly pointed internal 

acoustic meatus of the periotic; small and subcircular aperture 

for the vestibular aqueduct, roughly the size of the aperture for 

the cochlear duct; posterior process of periotic elongated with 

a fingerlike apex; dorsoventrally highest part of the involucrum 

of the tympanic bulla in medial view located in anterior half of 

the tympanic bulla; fused and elongated mandibular symphysis 

making about 60% of rostrum length; premaxillary and anterior 

dorsal infraorbital foramen posterior to the level of the antorbital 

notch; enamel crown of teeth conical and curved medially, lacking any ornamentation or accessory denticles; height of crown 

up to 6 mm; and enamel base of crown up to 3 mm in diameter.

Description. Rostrum: The rostrum of this small dolphin is elongated and narrow, with the ratio of length/width at 

the base of rostrum equal to 3.25 (Figure 2.48). Width at rostrum base is slightly greater than in Kentriodon pernix (USNM 

V 10670) and Pithanodelphis cornutus (USNM PAL 187575).

Premaxilla. In CMM-V-8343, the right premaxilla 

is well preserved from the level of the premaxillary foramen 

forward (Figure 2.48). In dorsal view throughout its length, 

the premaxillae present a dorsally open mesorostral canal. In 

CMM-V-8343, the left premaxilla has been crushed somewhat 

medially, artificially narrowing the width of the dorsal opening 

of the canal. Nevertheless, the posterior half of the latter was 

only narrowly open dorsally. Conversely, the anterior half of the 

mesorostral canal becomes increasingly open.

The posteriormost part of the premaxilla that is preserved 

on the rostrum presents a nearly horizontal, slightly transversely 

convex surface. As one follows the premaxilla forward, this convex surface in the horizontal plane turns increasingly vertical 

such that it is nearly so at its anteriormost extremity. A shallow trough marks the horizontal suture between the premaxilla 

and maxilla. The trough becomes increasingly shallow anteriorly 

where the two bones appear to be inextricably fused. There appears to have been room for two, perhaps three, tooth alveoli in 

the premaxilla.

The right premaxillary foramen is located just posterior to 

the level of the antorbital notch. Only the anteriormost part of 

the right premaxillary sac fossa is preserved.

Maxilla. The right maxilla is preserved from its contribution to the supraorbital process to its anteriormost extremity 

(Figure 2.48). It feathers out laterally onto the supraorbital process 

of the frontal, such that the frontal is clearly visible in dorsal view 

lateral to the maxilla. Although incomplete in this area, the maxilla does not appear to have contributed to the development of 

any supraorbital crest. At rostrum base, the dorsal exposure of 

the maxilla is not significantly wider than the premaxilla, differing 

on that point from the holotype of Pictodelphis kidwellae gen. et 

sp. nov. (see below). Furthermore, the dorsal surface of the bone 

is not inflated in the area anterior to the antorbital notch, further 

differing from P. kidwellae. A single dorsal infraorbital foramen 

lies posteromedial to the antorbital notch. Immediately medial to 

this foramen, the lateral margin of the premaxilla is marked by a 

shallow indentation to accommodate the foramen. The maxilla 

contributes to the formation of the antorbital notch (posterior and 

medial walls). From this point forward in dorsal view, the maxilla 

is increasingly obscured as it passes below the premaxilla.

In lateral view, the entire alveolar groove is visible (Figure 

2.48B). The well-formed circular alveoli bow along the ventrolateral margin of the maxilla. In that same view, the maxilla thins 

to a blunt point anteriorly, where it nearly completely fuses with 

the premaxilla. In ventral view, the tooth rows converge before 

turning slightly, such that at about their midpoint forward, the 

contralateral rows of alveoli are nearly parallel (Figure 2.48C). At 

least 55 maxillary alveoli are counted on the right side, which is 

one of the greatest tooth counts among early delphinidans, greater 

than in Brevirostrodelphis dividum, Kentriodon pernix, Pictodelphis kidwellae gen. et sp. nov. (see below), Rudicetus squalodontoides, Tagicetus joneti, and Westmorelandelphis tacheroni gen. 

et sp. nov. (see below). An even greater tooth count is seen in 

longirostrine forms like Belonodelphis peruanus and the lipotid 

Parapontoporia spp. (Barnes, 1985b; Muizon, 1988b). The largest alveoli have a transverse diameter of 5 mm, whereas most 

range between 4.2 and 4.5 mm, and the four posteriormost are 

smaller than 4 mm. Interalveolar septa are very thin, sometimes 

less than 0.5 mm. The alveolar groove ends 27 mm from the antorbital notch. For approximately three-quarters of the anterior 

length of the tooth row, a conspicuous trough separates the maxillae in ventral view. There is no sign of the palatal component of 

the vomer within this trough. Posteroventrally, the ventral surface 

of the maxilla is marked by sutural furrows for articulation with 

the palatines. Anterior to the palatines, the palate is transversely 

convex but not keeled.

Vomer. In a left medial view of CMM-V-8343 where 

the left premaxilla and maxilla have broken away, the vomer 

presents as a thin lamina that lines the lateral wall of the mesorostral canal. The vomer rises to the level of the maxillary-premaxillary suture. Ventrally (Figure 2.48C), the vomer forms the 

wafer-thin medial lamina separating contralateral palatines and 

pterygoids. Posteriorly in CMM-V-8343, the vomer surrounds 

the cancellous bone of the presphenoid.

Frontal. The only part of the right frontal that is preserved consists of its contribution to the formation of the supraorbital process (Figure 2.48). In lateral view, the preorbital 

process is triangular and moderately thickened, being markedly 

thicker than the overlying maxilla.
NUMBER 107 • 137

Lacrimal. The relatively large right lacrimal is well 

preserved, forming the lateral margin of the antorbital notch and 

the anteromedial, anterior, and anterolateralmost margins of the 

supraorbital process (Figure 2.48). Unfortunately, ventrally, surface damage to the bone obliterated details of its morphology. In 

lateral view, it is exposed anteroventrally to the preorbital process of the frontal as a thick stripe of bone.

Jugal. Medial to the lacrimal and antorbital notch, only 

the root of the styliform process of the jugal is preserved (Figure 

2.48C). Bone surface damage in this area obscures other details.

Palatine. Much of the right palatine is preserved in 

situ. The anterior reach of this bone is approximately 20 mm anterior to the level of the antorbital notch. On the basis of the outline of the sutural surfaces with the maxillae, the anterior margin 

of the joined palatines was most likely W shaped, with a posteromedial wedge of maxillae exposed between apices of right 

and left palatines. The anterior tip of the right pterygoid sinus 

fossa is preserved, being narrow and reaching a level at least 

16 mm anterior to the antorbital notch; this is longer than in 

Brevirostrodelphis dividum and Rudicetus squalodontoides.

Squamosal. The anterior portion of the right zygomatic 

process is preserved. Its maximum dorsoventral height is 18.5 mm. 

The anterodorsal corner of the process is more anterior than the anteroventral corner (a condition similar to Pithanodelphis cornutus

IRSNB M.373), both regions being transversely thickened. The ventral margin of the process is slightly concave in lateral view. A short 

portion of the tympanosquamosal recess is visible along the dorsomedial margin of the process, being proportionally markedly narrower than in P. cornutus IRSNB M.373 and USNM PAL 187575.

Occipital. Transversely thin in its anterior portion, 

the basioccipital crest thickens backward. It is shorter ventrally 

than the paroccipital process of the exoccipital. The jugular notch 

is deeper than wide, not as slit-like as in P. cornutus (IRSNB 

M.373). The ventral margin of the paroccipital process is 

slender, and an oblique groove extends ventromedially along its 

anterior flank.

Periotic. The right periotic in CMM-V-8343 is complete (Figure 2.49). In its overall shape (ignoring the obvious size 

difference), it most closely resembles the periotic of Macrokentriodon morani (Figure 2.42C,D), especially in the pointed and 

elongate posterior process. The periotic in Herbeinodelphis nancei differs from that of Macrokentriodon in only the following 

ways: (1) it is much smaller, 64% the length of the periotic in the 

holotype specimen of M. morani; (2) it is not nearly as rugose as 

in the latter; and (3) in M. morani, the opening for the vestibular 

aqueduct approximates a compressed oval, whereas in H. nancei

it is roughly circular.

In CMM-V-8343, the anterior process of the periotic is short 

and slender, modestly well developed (see Table 2.4), directed anteromedially and slightly ventrally, with a blunt apex in both ventral and medial views. In ventral view (Figure 2.49A), the anterior 

process presents a concave fovea epitubaria anterior to the broken 

base of the anterior pedicle. Medial to the broken pedicle, the pars 

cochlearis is strongly hemispherical. It is punctuated only by the 

large fenestra rotunda (maximum diameter = 2.6 mm), the small and 

subcircular aperture for the cochlear aqueduct (diameter less than 

1 mm), the barely larger and subcircular aperture for the vestibular 

aqueduct in large depression, and the large, strongly anterolaterally 

TABLE 2.4. Measurements of the holotype skull (including ear bones) of Herbeinodelphis nancei

gen. et sp. nov., CMM-V-8343. Symbols: asterisk (*) = estimated measurement.

Measurement

Dimension (mm)

Condylobasal length (estimate) 400

Rostrum length (base rostrum-anterior premaxilla) 273

Width of rostrum at anterior maxilla 19

Width of rostrum at base 84

Width of premaxillae at rostrum base 44*

Height of rostrum at anterior maxillae 12

Height of rostrum at base 42

Length of right periotic 27.5

Length of anterior process of periotic 5.5

Length of pars cochlearis until fenestra rotunda 9.0

Length of posterior process of periotic 12.9

Length of right tympanic bulla (excluding posterior process) 28.8

Maximum width of tympanic bulla 16.5

Maximum height of involucrum 8.0
138 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

pointed internal acoustic meatus (10 mm long; Figure 2.49B,C). 

In the latter, the crest separating the foramen singulare from the 

spiral cribriform tract is only slightly higher than the crest between 

the foramen singulare and the proximal opening of the facial 

canal. The area between the aperture for the vestibular aqueduct 

and the internal acoustic meatus is low, lacking the high pyramidal 

process of Macrokentriodon morani. A well-defined medial promontorial groove is present medial to the internal acoustic meatus. 

A marked stylomastoid fossa excavates the posterior base of the 

pars cochlearis, dorsolateral to the fenestra rotunda, as in several 

other early delphinidans, including Brevirostrodelphis dividum

and Westmorelandelphis tacheroni gen. et sp. nov. (see below). 

The dorsal process is low, projecting only 6 mm dorsal to the 

internal acoustic meatus. Still, the outline of this area in medial 

view is distinctly convex. The lateral tuberosity is as long laterally as anteroposteriorly thick. The hiatus epitympanicus is deep, 

extending posteromedially dorsal to the anteromedial margin of 

the posterior bullar facet. Facing posteromedioventrally, with a 

maximum diameter of 3.2 mm, the mallear fossa lies immediately 

distal to the broken base of the anterior pedicle. In turn, the tiny 

fossa incudis lies immediately posterior to the mallear fossa. Medial to the fossa incudis is the trough formed by the facial canal. 

The stapes was not preserved in the slightly anteromedially elongated fenestra ovalis. Posterior to the fenestra ovalis is the deep 

fossa for the stapedial muscle, the distal end of which is mostly 

obscured in a ventral view by the medial reach of the posterior 

bullar facet (=facial crest of the periotic). Differing from the condition in M. morani, the lateral caudal tympanic process (see Lambert et al., 2017c) is not well defined, making a smoothly rounded 

margin also overhanging the fossa for the stapedial muscle. The 

proximally wide, posterior bullar facet is broadly transversely and 

longitudinally concave, and it preserves an elongate and pointed 

posterior process. The pointed, fingerlike posterior extremity of 

the process curves gently ventrally (Figure 2.49B,D). No major 

ridge is observed on the posterior bullar facet.

Tympanic Bulla. The right tympanic bulla in CMMV-8343 is virtually complete (Figure 2.50), having suffered very 

little breakage. Most of its outer surface is textured. In its overall shape, it most closely resembles the bulla in Hadrodelphis 

calvertense (Figure 2.37C–E; the bulla is not known in Macrokentriodon morani). The bulla in Herbeinodelphis nancei differs from that of H. calvertense in only the following two ways: 

(1) it is distinctly smaller, being 67% the length of the bulla in 

H. calvertense CMM-V-11, and (2) it is not nearly as rugose as 

in H. calvertense. Aside from these differences, a written description alone would be inadequate to distinguish between these two 

tympanic bullae.

Matching the outline of the posterior bullar facet of the periotic, the posterior process is proximally broad, proportionally 

large and elongate (13 mm), exhibiting a posterolateral orientation (Figure 2.50). The facet for the posterior process of the periotic is markedly anteroposteriorly convex and slightly transversely 

convex. The tympanic notch separates the anterior end of the posterior process from the sigmoid process. An elliptical foramen is 

present ventral to the posterior process with a maximum diameter 

of about 2.4 mm. The base of the inner posterior pedicle is salient, 

making a crest that turns anterodorsally. The prominent, posteroventrally trending and long lateral furrow marks the lateral side 

of the bulla for two-thirds of its height. As in Hadrodelphis calvertense, the lateral furrow is closer to the sigmoid process than 

being midway between the anterior extremity of the periotic and 

the sigmoid process, as seen in K. pernix (Dawson, 1996). The 

sigmoid process is anteroposteriorly thin (2.6 mm at mid-length) 

and transversely directed. The mallear ridge is low and directed 

posteromedially. The conical process is broad at its base in lateral 

view but dorsally low. The dorsal margin of the high involucrum 

only slightly descends posteroventrally from a maximum height 

in the anterior third. In ventral view (Figure 2.50C), a deep and 

narrow interprominential notch separates the outer and inner posterior prominences, the inner prominence being slightly shorter 

posteriorly and transversely narrower than the outer prominence. 

With a sigmoid outline, the median furrow extends far anteriorly, 

until 7 mm from the anterior tip of the bone. 

Mandibles. On the slender mandibles, the long mandibular symphysis (=164 mm) is fused (Figure 2.51). The height 

of the mandible at the posterior end of the symphysis is 21 mm, 

with a width of 29.7 mm. On the left side, the tooth count is 

56, including 21 alveoli posterior to the symphysis. Two large 

mental foramina are observed on each side, followed anteriorly 

by sulci. An additional smaller foramen is visible on the right 

side, at mid-height and 25 mm posterior to the end of the symphysis. The ventral margin of the mandible turns anterodorsally, 

being convex in lateral view in the symphyseal part and slightly 

concave posterior to the symphysis. The left coronoid process is 

incomplete, and the height of the dorsal margin of the mandible 

only gradually increases posteriorly. The mandibular condyles 

and angular processes were not preserved.

Teeth. All the preserved small teeth are conical and lack 

any ornamentation or accessory denticles (Figure 2.48D), even the 

posteriormost ones, differing from Brevirostrodelphis dividum, 

Pictodelphis kidwellae gen. et sp. nov. (see below), and Rudicetus squalodontoides. Some degree of apical abrasion is observed. 

Small attritional facets are present along the distal face of the four 

upper teeth preserved in situ and along the mesial face of the two 

posteriormost lower teeth. The enamel crown of the teeth curves 

medially, with a height of 6 mm. The base of the crown is as much 

as 3 mm in diameter. At the base of the enamel neck of the tooth, 

the diameter of the root cementum increases, unlike in Kentriodon 

pernix, in which “the enamel passes into the cementum of the root 

very gradually, without any perceptible increase or decrease in the 

diameter of the neck” (Kellogg, 1927a:34).

Cervical Vertebrae. Measurements for the cervical vertebrae preserved in CMM-V-8343 are given in Table 2.5.

There is no fusion between any of the cervical vertebrae (Figure 

2.52), although the bodies of the vertebrae are anteroposteriorly compressed. The epiphyses are fully fused in all the cervical 

vertebrae.
NUMBER 107 • 139

The atlas and axis are the largest of the cervical vertebrae 

(Figure 2.52A–F), and the atlas is the longest. In an anterior view 

of the atlas (Figure 2.52A), the concave ear-shaped cranial articular foveae bracket the roughly triangularly shaped neural canal. 

The posterior articular foveae are smaller (Figure 2.52C) and 

approximate the outline of kidney beans. Dorsally, the neural 

arch comprises a relatively thin bridge of bone that connects the 

aforementioned facets.

In a lateral view of the atlas (Figure 2.52B), the lateral 

vertebral foramen conspicuously perforates the neural arch. 

The widest part of the atlas is formed by the transverse processes that terminate lateral to the caudal articular foveae. 

Ventral to and between these foveae is the tongue-shaped ventral tubercle (hypapophysis). It projects posteroventrally from 

the ventral arch to partially underlie the body of the axis, although it does not make contact with it. The odontoid process 

on the axis lies immediately above this tubercle and between 

the posterior foveae. Above each posterior articular fovea is 

a rounded flange that projects posterodorsolaterally from the 

base of the neural arch.

The atlas of Herbeinodelphis nancei is intermediate in size between that of the atlas of the type specimens of Kentriodon pernix

and Brevirostrodelphis dividum. It differs from that of K. pernix in 

the following ways: it is larger, its transverse processes are proportionately not as elongate, its posterior articular foveae are wider 

ventrally, and it has more distinct flanges above the posterior foveae. It differs from that of B. dividum in the following ways: it 

is smaller, they differ in the shapes of their anterior and posterior 

articular foveae, and the atlas of H. nancei has more pronounced 

transverse processes, a longer tongue-shaped ventral tubercle, and 

more distinct flanges above the posterior foveae.

The axis is the highest and widest of the cervical vertebrae (Figure 2.52D–F). It too is intermediate in size between 

those of K. pernix and B. dividum. The backward-inclined 

neural spine is approximately triangular in section, presenting 

a strong carina anteriorly, whereas a concave trough occupies 

the length of its posterodorsally trending posterior margin. 

The postzygapophyses are nearly horizontal and situated at 

the level of the top of the neural canal. Medial carinae mark 

the base of the neural canal and the ventralmost surface of 

the centrum. Corresponding depressions occupy either side of 

these longitudinal ridges. A strong arc-shaped horizontal carina marks the apex of the odontoid process. On either side 

of the odontoid process, the anterior articular facets approximate the shape of those on the posterior face of the atlas. 

Lateral to these are the oblique, backward and outwardly directed robust transverse processes. They are proportionately 

more gracile than those in B. dividum.

The remainder of the cervical vertebrae (Figure 2.52G–L) 

differ from one another mostly in the shape of their neural 

canal and in the length and orientation of their upper and 

lower transverse processes. In the third cervical (Figure 

2.52G), the neural canal is semicircular in outline, and the 

backwardly swept transverse processes are nearly horizontal. 

A modest elliptically shaped vertebrarterial canal pierces the 

dorsal half of the transverse process immediately adjacent to 

the centrum. In the fourth cervical (Figure 2.52H), the neural 

canal is more compressed dorsoventrally (although some of 

that compression is due to postmortem deformation), and the 

vertebrarterial canal is much larger. Furthermore, the root of 

each lower transverse process originates from the ventrolateral side of the centrum rather than from its lateral face as in 

the third cervical.

In the fifth cervical (Figure 2.52I), the neural canal is ovoid 

in outline, the centrum is nearly circular in anterior view, and 

the lower transverse process is distinct from the upper transverse process, although a thin splint of bone joins the two, enclosing the large vertebrarterial canal. The shape of the neural 

TABLE 2.5. Measurements (mm) of the holotype cervical vertebrae of Herbeinodelphis nancei gen. 

et sp. nov., CMM-V-8343. Abbreviations and symbols: X = broken bone; c = neural arches slightly 

compressed ventrally.

Dimension Atlas Axis 3rd 4th 5th 6th 7th

Greatest depth (vertically) of 50.0 78.0 42.5 43.5c 41.0c 40.5c 42.0

vertebra (tip of neural spine 

to inferior face of centrum)

Length of centrum 27.5 26.0 10.5 10.5 10.5 11.5 12.0

Distance across vertebra 71.5 85.0 71.0 62.5 60.0 67.5 77.5

between tips of transverse 

processes (parapophyses)

Distance between tip of right X X 16.5 X 18.0 20.0 25.0

postzygapophysis and tip of

right prezygapophysis

Minimum anteroposterior X X 8.5 9 7 6.5 7

diameter of neurapophysis
140 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

canal and the outline of the centrum in the anterior view of 

the sixth cervical (Figure 2.52J,K) are very much like those of 

the fifth cervical. The sixth cervical differs from other cervicals in that it possesses greatly elongate posteroventrolaterally 

directed lower transverse processes. Throughout their length, 

the anteroposterior width of these processes matches the thickness of the centrum (Figure 2.52K). The ventrolaterally directed upper transverse processes are gracile by comparison. 

The lower transverse processes in K. pernix differ from those 

in H. nancei in that in the former they are directed almost entirely ventrally (Kellogg, 1927a). In the holotype of B. dividum

(True, 1912), the sixth cervical still encloses a large vertebrarterial canal that is not present in H. nancei.

The upper transverse processes of the seventh cervical 

(Figure 2.52L) are directed nearly completely laterally. There is 

no development of lower transverse processes, the area being 

occupied instead by an articular facet for the capitulum of the 

first rib.

Thoracic Vertebrae. Measurements for the thoracic vertebrae preserved in CMM-V-8343 are given in Table 2.6. 

The epiphyses are fully fused in all the thoracic vertebrae 

(Figure 2.53A–F). The first seven thoracic vertebrae are superbly 

well preserved. The outline of the centrum in the first thoracic 

vertebra is oval. The articular surfaces for the tuberculum 

of the ribs are large and saddle shaped. On either side of the 

posterodorsolateral margin of the centrum is the large facet that 

held the capitulum of the rib. The neural spine is bladelike, 

tapering distally.

The facet on the diapophysis in the second thoracic vertebra 

is smaller than in the first thoracic and more nearly semicircular 

in outline. The facet for the capitulum is also reduced in size 

compared to that in the first thoracic vertebra. The neural spine 

expands slightly distally, and it hosts a shallow trough medially 

along its ascending posterior face.

The description given by Kellogg (1927a) for the thoracic vertebrae in Kentriodon pernix would also describe 

those in Herbeinodelphis nancei. They differ mostly in size; 

the sixth thoracic of the type of K. pernix is 74% the height 

of the same thoracic vertebra in the holotype of H. nancei. 

They differ from those in the holotype of Brevirostrodelphis 

dividum in that they are slightly smaller (the fifth dorsal in H. 

nancei is approximately 94% the height of the same vertebra in 

B. dividum) and the neural spines are more inclined posteriorly in 

H. nancei (Figure 2.53F) than in B. dividum (True, 1912: plate 20).

Caudal Vertebrae. CMM-V-8343 also preserves 

two caudal vertebrae (Figure 2.53G–I); their epiphyses are fully 

fused. Figure 2.53G,H shows the one peduncular vertebra 

with its greatly reduced neural spine. Vertebral height is its 

TABLE 2.6. Measurements (mm) of the thoracic vertebrae in the holotype of Herbeinodelphis nancei gen. 

et sp. nov., CMM-V-8343. Abbreviations and symbols: Dash (—) = no facets for tubercula; X = broken bone; 

c = neural arches slightly compressed ventrally; n/a = not available.

Dimension 1st 2nd 3rd 4th 5th 6th 7th 8th

Greatest depth (vertically) of 67.0 83.0 87.0 88.0 91.0 91.0 84.0c X

vertebra (tip of neural spine

to inferior face of centrum)

Height of anterior face of 23.5 23.5 24.0 23.5 24.0 23.5 25.0 26.0

centrum

Breadth of centrum posteriorly 35.5 40.5 40.5 36.5 33.5 — — —

across facets for capitulum

Length of centrum 16.5 21.5 26.0 28.0 30.5 33.0 35.5 39.0

Distance across vertebra 74.5 73.0 72.0 69.0 70.5 n/a n/a n/a

between tips of diapophyses

Distance across vertebra n/a n/a n/a n/a n/a 67.0 70.0 78.0

between tips of transverse 

processes (parapophyses)

Minimum length of 9.0 10.5 12.0 12.5 13.5 14.0 14.5 17.0

neurapophysis

Vertical height of neural spine 27.0 42.0 42.0 45.0 48.5 49.5 41.0c X

(distance between superior 

margin of neural canal and 

tip of spine)

Minimum anteroposterior 8.5 11.0 9.0 10.0 12.0 14.0 14.0 X

diameter of the neural spine
NUMBER 107 • 141

greatest dimension (40.5 mm), followed by anteroposterior 

length (35.5 mm), then width (31.0 mm). Cylindrical best describes the overall shape of this vertebra. Its neural arch is 

small. The maximum diameter of the neural canal is 2 mm. At 

about the midpoint in the length of the centrum, tiny bilateral 

arterial foramina are seen below and adjacent to the neural 

arch and pass vertically through the body of the centrum. 

Ventrally, these foramina open on the ventrolateral surface 

of the centrum and within the longitudinal excavation created 

between the ridges, the ends of which each held a chevron. 

Figure 2.53I pictures a distal caudal vertebra that is wider 

(34.5 mm) than high (24 mm), indicating that it was within 

the body of the fluke. Three vertebrarterial foramina are present on its dorsal surface and variously pass vertically through 

the centrum to open ventrally as two smaller bilateral foramina and one large medial foramen.

Ribs. Five virtually complete ribs are preserved in 

CMM-V-8343 (Figure 2.54). Unfortunately, because they were 

disarticulated from their vertebrae, assignments are tentative.

Judging from its size and shape, Figure 2.54A represents 

the first right rib. Its maximum straight-line length is 105 

mm. This rib is flattened throughout its length. As in Kentriodon pernix (Kellogg, 1927a), the ovoid face of the capitulum is borne on a short, thick neck. The tuberculum is 

larger than the capitulum. Beyond the tuberculum, the shaft 

turns at right angles and is nearly straight throughout the 

rest of its length. The distal end of this rib is not expanded 

for the attachment of the sternal rib. Figure 2.54B is either 

the second or third left rib (reflected in the figure for ease 

of illustration). Its maximum straight-line length is 197 mm. 

It presents a longer neck between the nearly equally sized 

capitulum and tuberculum. The curving shaft is not as broad 

as in the first rib. The distal extremity of the rib expands 

for attachment of the sternal rib. Figure 2.54C is the third, 

fourth, or fifth left rib (reflected in the figure for ease of illustration). Its maximum straight-line length is 235 mm. Its 

articular surfaces are nearly identical to those of the preceding rib. Its shaft is further reduced in width compared to the 

preceding rib, although distally, the shaft expands modestly. 

The distal extremity of the rib expands for attachment of the 

sternal rib. Figure 2.54D is the fourth, fifth, or sixth right 

rib. Its maximum straight-line length is 257 mm. Its articular 

surfaces are reduced in size compared to those of the preceding rib, as is the diameter of its shaft. The distal extremity 

of the rib does not expand for attachment of a sternal rib. 

Figure 2.54E is either the seventh rib or one posterior to that 

point. It is nearly identical to the preceding one except that 

it presents a single articular head. Distally, it appears that in 

life, there was still attachment of a sternal rib.

In Kentriodon pernix, the eighth rib articulates only with 

the diapophysis, and the ninth and tenth ribs articulate with the 

parapophyses (transverse processes). Conversely, in Herbeinodelphis nancei, it is the single-headed seventh rib that articulates 

only with the diapophysis and the eighth and succeeding ribs 

that articulate with the parapophyses.

Remarks. The following features evidence the osteological maturity (Galatius and Kinze, 2003; Moran et al., 2015) 

of this small odontocete: teeth are embedded in well-defined 

circular alveoli, the dark enamel crowns of some teeth exhibit 

significant tooth occlusal wear, and epiphyses for all preserved 

vertebrae and pectoral limb elements are fully ankylosed. Furthermore, the carpals, metacarpals, and phalanges also appear 

well ossified.

Herbeinodelphis differs from other comparable odontocetes 

in the following ways. In Kentriodon pernix, Kellogg (1927a) 

claimed that there were eight teeth per side in each premaxilla, 

whereas in Herbeinodelphis nancei there seem to be only two 

teeth per premaxilla, perhaps three. The rostrum of Herbeinodelphis is proportionally longer than in K. pernix and Brevirostrodelphis dividum. In its overall size, it is much smaller than 

Hadrodelphis calvertense, Macrokentriodon morani, Miminiacetus pappus, and Cammackacetus hazenorum gen. et sp. nov. 

(see below) and smaller than Pictodelphis kidwellae gen. et sp. 

nov. (see below) and Westmorelandelphis tacheroni gen. et sp. 

nov. (see below).

Some of the differences between Herbeinodelphis and Rudicetus squalodontoides from the Miocene of Italy (Bianucci, 

2001) include the following: the skull of Rudicetus is larger than 

that of Herbeinodelphis (based on a postorbital width in the former of 162 mm in the referred specimen of R. squalodontoides); 

the tooth count is much lower in Rudicetus, with only about 30 

teeth per row, whereas there are 57–58 teeth present per row 

in Herbeinodelphis; the alveoli are larger in Rudicetus as well; 

and the rostrum is also proportionally shorter in Rudicetus (the 

ratio between the postorbital width and rostrum length is greater 

than in Herbeinodelphis). Herbeinodelphis differs from Tagicetus joneti from the Middle Miocene of Portugal (see Lambert 

et al., 2005) in the following major ways: Tagicetus is larger 

(based on a postorbital width of 166 mm), it has a much lower 

tooth count of approximately 22 maxillary alveoli compared to 

55 in the maxilla in Herbeinodelphis, and the alveoli are also 

larger. Herbeinodelphis also differs from Kentriodon hoepfneri

from the Middle to early Late Miocene of Germany (see Kazár 

and Hampe, 2014) in that the anterior process of the periotic 

is directed more anteromedially in K. hoepfneri, the posterior 

process of the periotic is most likely shorter in K. hoepfneri, the 

aperture for the endolymphatic duct is much larger in K. hoepfneri, and the lower transverse process of the atlas is more robust 

in K. hoepfneri, on a transversely wider atlas.
Cammackacetus gen. nov.

FIGURES 2.55, 2.56

Cammackacetus hazenorum

(Illustration by Tim Scheirer)

Type and Only Included Species. Cammackacetus hazenorum.

Etymology. The generic epithet Cammackacetus

honors the late David S. Cammack, who purchased the skull and 

originally loaned it to Frank C. Whitmore Jr. at the USNM, plus 

ketos, Greek for a large sea animal or whale, here using the Latin 

form of the noun, cetus. The letter “a” between Cammack and

cetus was added for ease of articulation.

Diagnosis of Genus. As for the type and only species.

Cammackacetus hazenorum sp. nov.

Holotype. USNM PAL 639715 (Figures 2.55, 2.56), 

a partial skull lacking the distal part of the rostrum, the supraorbital processes, most of the squamosals, and the ear bones. 

Following the initial loan, David Cammack’s estate donated the 

skull to the USNM after his death.

Type Locality. Found in the shallow waters of the 

Chesapeake Bay, just offshore from Governor Run, Calvert 

Cliffs, Calvert County, Maryland.

Horizon and Age. Although the specimen was not 

found in situ, an analysis of microfossils found in sediment attached to the skull is indicative of the St. Marys Formation (SZ 

24), Chesapeake Group, Late Miocene. Unfortunately, the place 

where the skull was found is not known to preserve sediments 

from SZ 24. Therefore, location and apparent horizon are not 

congruent.

Known Range. Only tentatively known from SZ 24, 

Windmill Point Member (Tortonian) of the St. Marys Formation.

Etymology. The specific name honors Robert and 

Margaret “Margee” Hazen for their many contributions in numbers of fossils, minerals, and financial support to the Department 

of Paleontology at the CMM. “Orum” was added as a suffix to 

“Hazen” according to the ICZN (International Commission on 

Zoological Nomenclature, 1999) for a species named in honor of 

more than one person, among other conditions.

Referred Material. None at this time.

Diagnosis of Species. Robust delphinidan characterized by the following unique combination of characters: 

massive, transversely and dorsoventrally thick premaxillae at 

mid-length of rostrum; no significant constriction of the lateral 

margins of premaxillae in rostrum base; slightly transversely 

concave premaxillary sac fossae; well-developed premaxillary 

crest lateral to the posterior margin of the bony nares, with a 

prominent dorsolateral corner; reduced contact between premaxilla and nasal along anterolateral corner of the latter; minimum width of vertex greater than width of bony nares; nasal 

wider than long; lateral margins of nasals diverging posterolaterally; dorsal surface of nasal sloping markedly anteroventrally; 

frontal wider than nasal on vertex and reaching a slightly higher 

level; nuchal crest barely anteriorly projected, with supraoccipital shield only a little exposed in dorsal view; occipital shield 

inflated, being dorsoventrally convex; temporal crests converging ventromedially in posterior view; large maxillary alveoli, up 

to 17 mm in transverse diameter; W-shaped palatine-maxilla sutures with posteromedial exposure of maxillae between apices 

of palatines; pterygoid sinus fossa reaching the level of the antorbital notch; and fossa for the postorbital lobe of the pterygoid 

sinus being very deep and posteriorly defined by a high crest.

Description. Somewhat smaller than the skull of 

the holotype of Macrokentriodon morani (based on the smaller 

width of the premaxillary sac fossae and bony nares), USNM 

PAL 639715 (Figures 2.55, 2.56) is a large skull (Table 2.7) 

with a robust rostrum, proportionally large and well-defined 

alveoli, and thick nuchal and temporal crests. Such robustness and the closure of cranial sutures indicate a fully mature 

adult individual. Whereas the apex of the rostrum is missing, 

together with part of its lateral margins at rostrum base, the 

width and height of the maxillae and premaxillae at the preserved anterior end suggest a rather elongated rostrum, not 

differing much from M. morani. The proximal part of the rostrum is proportionally wider in Hadrodelphis calvertense, with 

the alveolar grooves diverging more markedly laterally beyond 

the level of the lateral margin of the choana. The moderately 

elevated vertex is considerably wider than in H. calvertense, 

Miminiacetus pappus, Lophocetus calvertensis, and, to a lesser 

extent, M. morani. The temporal fossa is high, extending far 

posterodorsally (minimum height from the partly preserved 

floor of squamosal fossa = 125 mm).

Premaxilla. Each premaxilla is robust anteriorly, 

being thick and broad with a transversely convex dorsal surface 

(Figure 2.55). A few tiny foramina (diameter ≤ 1 mm) pierce 

the dorsal surface of each premaxilla (three on the right, two 

on the left) in the rostral region. The contralateral premaxillae 

contact each other at their preserved anterior end, whereas the 

medial margins gradually diverge posterolaterally. Just anterior 

to the premaxillary foramina, the maximum width of the dorsal 

opening of the mesorostral canal is 15.5 mm. More posteriorly, 

the two bones only slightly converge, remaining distant at the 

anterior end of the bony nares (12.6 mm). The lateral margins 

of premaxillae are barely constricted at rostrum base, less than 

142 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
 143

FIGURE 2.55. Cammackacetus hazenorum gen. et sp. nov. USNM PAL 639715, holotype, partial skull lacking the distal part of 

the rostrum, the supraorbital processes, most of the squamosals, and the ear bones. (A) Dorsal view. (B) Right lateral view. (C) 

Left anterodorsolateral view.
FIGURE 2.56. Cammackacetus hazenorum gen. et sp. nov. USNM PAL 639715, holotype, partial skull lacking the distal 

part of the rostrum, the supraorbital processes, most of the squamosals, and the ear bones. (A) Ventral view. (B) Posterior 

view. (C) Right anteroventrolateral view.

14 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
NUMBER 107 • 145

in Hadrodelphis calvertense, Miminiacetus pappus, Lophocetus 

calvertensis, and Macrokentriodon morani. Each large premaxillary foramen (transverse diameter = 6.5 and 5.8 mm for right 

and left foramina, respectively) is anteroposteriorly elongated 

and followed anteriorly by a long anteromedial sulcus (approximately 80 mm). The prenarial triangle is transversely concave, 

with the medial margin being higher. Whereas no posteromedial 

sulcus is evident, the posterolateral sulcus is visible for only a 

short distance, disappearing before mid-length of the bony nares. 

The premaxillary sac fossae are slightly transversely concave and 

moderately anteroposteriorly concave, with a gradual elevation 

toward the vertex. At the level of the posterior margin of the 

bony nares, each premaxilla retains a considerable width, with a 

prominent posterolateral corner making an angle of about 90° in 

anterior view and overhanging the maxilla. Such a condition is 

reminiscent of the premaxillary crests of ziphiids, especially the 

condition in berardiines with transversely directed crests (e.g., 

Bianucci et al., 2007), whereas the premaxillary crest is narrower, less dorsolaterally protruding in M. morani and absent 

in H. calvertense. The anterodorsal surface of the premaxillary 

crest does not attain a vertical orientation, and its dorsal edge is 

considerably lower than the top of the nasal and frontal on the 

vertex. A vertical foramen is observed along the posterior wall of 

the premaxillary crest, at about mid-length, on the suture with 

the maxilla. Each premaxilla contacts the corresponding nasal 

along the posterolateral corner of the latter on a shorter length 

(suture of about 10 mm in dorsal view) than in Kampholophos 

serrulus, Miminiacetus pappus, and M. morani.

Maxilla. At the preserved anterior end of the rostrum, 

the dorsal exposure of the maxilla is narrow. The lateral margin 

of the bone rises toward the antorbital region, being concave 

in dorsal view. A tiny foramen is present along the suture with 

the premaxilla 80 mm anterior to the left premaxillary foramen 

(diameter = 1 mm) and 60 mm anterior to the right premaxillary foramen (diameter = 1.5 mm). Two large dorsal infraorbital 

foramina are preserved on the left maxilla: the anterior foramen 

has a diameter of 9 mm and opens anterolaterally, and the posterior foramen is more distant from the premaxilla, has a diameter 

of 8.2 mm, and is not followed by a sulcus. A tiny foramen (diameter = 1.5 mm) lies between the two large foramina, whereas 

a second small foramen (diameter = 3 mm) is posterolateral to 

the posteriormost large foramen and opens anterolaterally. On the 

right side, one large foramen (anteroposterior diameter = 22 mm) 

is located lateral to the premaxillary foramen, and a smaller 

foramen (transverse diameter = 2.5 mm) is just posterolateral. 

In the area of the antorbital notch, the dorsal surface of the 

left maxilla rises posterodorsally (the more posterolateral part 

was, unfortunately, lost). The maxilla is exposed medial to the 

TABLE 2.7. Measurements of the holotype skull of Cammackacetus hazenorum gen. et sp. nov., 

USNM PAL 639715. Symbols: asterisk (*) = estimated measurement.

Measurement

Dimension (mm)

Width of premaxillae at anterior end of rostrum as preserved 60

Width of premaxillae at level of anterior margin of right premaxillary foramen 87

Width of premaxillary sac fossae 121

Width of right premaxillary sac fossa 48

Width of left premaxillary sac fossa 50

Width of bony nares 56.5

Width across premaxillary crests on vertex 115

Maximum width of nasals 84

Maximum width of right nasal 41.5

Maximum width of left nasal 43

Minimum distance between maxillae across vertex (at anterolateral corner of nasal) 74

Distance between anteromedial margin of nasal and posteromedial margin of nuchal crest 57

Minimum distance between temporal crests 105

Maximum width of occipital shield 183

Width of occipital condyles 109

Width of foramen magnum 41

Oblique height of right occipital condyle 57.5

Width of right occipital condyle 45.5*
146 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

premaxilla at the anterior margin of the bony nares, making the 

latter U shaped. A posterior dorsal infraorbital foramen is partly 

preserved on the left side, about 15 mm from the premaxilla. 

On the right side, the posterior foramen is 20 mm lateral to the 

premaxilla, with a transverse diameter of 9.5 mm. The medial 

margin of the maxilla along the vertex is vertical, and the minimum distance between right and left maxillae is at the level of 

the anterolateral corner of the nasal. The posterior margin of the 

maxilla along the nuchal crest is directed posterolaterally.

In ventral view (Figure 2.56), seven large alveoli opening anteroventrally and slightly laterally are preserved on the left side, 

and six are preserved on the right, along the lateral margin of 

the maxilla. Transverse diameters for right alveoli range from 

17 mm anteriorly to 12 mm posteriorly. These dimensions are 

close to those in Hadrodelphis calvertense, with a larger skull in 

the latter. Interalveolar septa have a mean thickness of 2.7 mm. 

The last posterior alveolus is at least 60 mm anterior to the level 

of the approximate position of the antorbital notch. Lateral to 

the ventral exposure of the vomer on the rostrum, each maxilla 

is pierced by an opening that may correspond to the palatine fissure (see Fordyce, 2002; incisive foramen in Mead and Fordyce, 

2009). Each opening is followed anteriorly and anterolaterally 

by two sulci, one on the medial margin of the maxilla and the 

other on its ventral surface. A similar condition is observed in 

H. calvertense and Macrokentriodon morani. The palate is moderately transversely convex, with a low keel posterior to the anterior end of the palatine. Lateral to each palatine and reaching 

slightly anterior to the apex of the latter bone, a well-defined depression with a rounded anterior outline most likely corresponds 

to an area of origin for the pterygoid muscle (i.e., internal pterygoideus muscle; see Seagars, 1982, for extant delphinids).

Vomer. With a width of 8.5 mm, the vomer is exposed 

ventrally as a keeled medial surface at the preserved anterior end 

of the rostrum (Figure 2.56). In the anterior part of the basioccipital basin, the vomer sends a pair of projections along the 

medial walls of the basioccipital crests, with the medial portion 

of the bone being significantly shorter.

Presphenoid. The presphenoid is exposed dorsally 

between the premaxillary sac fossae. Its dorsal surface rises 

steeply posterodorsally, forming the nasal septum. The cribriform plate is exposed dorsally only in its medial portion, being 

elsewhere covered by the nasals.

Palatine. The palatine-maxilla suture is visible anteromedially, anteriorly, and somewhat anterolaterally (not to 

be confused with the greater palatine sulcus, visible on both sides 

because of partial removal of the palatine in this area; Figure 

2.56). The apex of the palatine is 110 mm anterior to the choana, and right and left sutures are W shaped because of a posteromedial exposure of the maxillae between the palatine apices. 

The lateral lamina of the palatine is partly crushed inside the 

anterior part of the pterygoid sinus fossa. The latter extends at 

least 50 mm anterior to the choana, thus reaching the level of the 

antorbital notch.

Pterygoid. The medial lamina of the pterygoid is 

partly preserved along the choana; its posteromedial suture with 

the vomer is distinct, and this lamina makes a thin plate along 

the anterior part of the basioccipital basin, joining posteriorly the 

basioccipital crest.

Nasal. Each nasal is wider than anteroposteriorly long, 

proportionally wider than in Kampholophos serrulus, Miminiacetus pappus, Lophocetus calvertensis, and Macrokentriodon 

morani. The lateral margins of the nasals diverge posterolaterally 

(Figure 2.55), differing from M. morani and Hadrodelphis calvertense. A broad, vertical notch excavates each anterior margin. 

Each nasal-frontal suture is posteriorly convex, and although the 

joined nasal-frontal sutures are V shaped with an anterior point, 

no marked wedge of frontals between nasals is observed. The 

highest part of each nasal is posterolateral, with the dorsal surface 

of each nasal sloping anteromedially. The lower medial portion 

corresponds to the presence of a shallow internasal fossa, and the 

anteroventral slope is reminiscent, although to a lesser extent, of 

the strong slope seen in H. calvertense, whereas no anteroventral 

slope is observed in M. morani. The suture between the nasals is 

shifted to the left by about 5 mm compared to the external occipital crest; together with a minor width difference between the 

nasals, it indicates weak asymmetry in the area of the vertex.

Frontal. Each frontal is slightly higher than the corresponding nasal (Figure 2.55); it is transversely broader and 

anteroposteriorly shorter, differing in these three points from 

Macrokentriodon morani. Each frontal is anteroposteriorly longer in Kampholophos serrulus and Miminiacetus pappus, and 

the frontal of Hadrodelphis calvertense is significantly higher 

than the nasal. The lateral portion of each frontal is squeezed between the inflated nasal and the locally thickened supraoccipital 

portion of the nuchal crest.

In ventral view, a deep fossa for the preorbital lobe of the 

pterygoid sinus is present on both sides, separated from the narrow frontal groove (10 mm wide at mid-length on left side) by a 

high and thin oblique plate. Defined posteriorly by a high crest, 

probably corresponding to the medial part of the infratemporal crest, the frontal groove broadens toward the orbital fissure. 

Posterior to this high crest, a deep fossa 36 mm long on the left 

side for the postorbital lobe of the pterygoid sinus is observed 

(Figures 2.55B, 2.56C). The posterior margin of this fossa is 

made of another high crest. This crest rises medioventrally, being 

the posterior margin of a vertical, wide groove posterior to the 

orbital fissure. The latter groove connects the sinus fossa in the 

alisphenoid to the fossa for the postorbital lobe in the frontal.

Supraoccipital. The nuchal crest is thick (minimum 

thickness = 25 mm on the left side and 21 mm on the right side), 

partly because of the development of a strong occipital protuberance on each anterolateral corner of the occipital shield (Figure 

2.55A). The occipital protuberances are located more medially 

in Macrokentriodon morani, the nuchal crest is projected farther 

anteriorly in Hadrodelphis calvertense and Kampholophos serrulus, and the nuchal crest is anteriorly pointed in Miminiacetus pappus. In dorsal view, the supraoccipital is seen to wedge 
NUMBER 107 • 147

slightly between the frontals. A thick, but short, external occipital crest is present in the upper part of the shield, a region 

that is markedly dorsoventrally and transversely concave (Figure 

2.55A). Ventrally, the aforementioned shield is inflated, more so 

than in H. calvertense and M. morani. The temporal crests are 

prominent (reaching a level 26 mm posterior to the medialmost 

part of the supraoccipital shield, at the narrowest level of the 

shield). Left and right crests converge ventromedially until they 

reach a level higher than the mid-height of the temporal fossae 

before diverging toward the floor of the temporal fossae.

Exoccipital. A deep dorsal condyloid fossa is present 

(Figure 2.56B). The occipital condyles are robust with a short 

condylar neck. The hypoglossal foramen is visible in the partly 

preserved right jugular notch.

Parietal and Interparietal. Although no dorsal 

exposure of the parietal or interparietal is seen in the area of 

the vertex, a triangular dorsal exposure of the parietal is distinct 

at the junction between the nuchal and temporal crests (Figure 

2.55A). The medial wall of the temporal fossa is laterally inflated. Sutures of the parietal with the squamosal and frontal are 

conspicuous in both temporal fossae.

Basioccipital. Each basioccipital crest thickens posteriorly, with the distal part diverging markedly posteroventrally 

(Figure 2.56). However, none of the crests is complete ventrally. 

A conspicuous crest, possibly for the rectus capitis muscle, begins medially on the posterior part of the basioccipital crest, then 

turns posteromedially to join its counterpart on the floor of the 

basioccipital basin.

Alisphenoid. The anteroventral surface of the alisphenoid is dorsoventrally convex and roughly transversely flat, 

except for its most ventrolateral portion, which is excavated by 

the path for the mandibular nerve V3. The latter turns anterolaterally from the foramen ovale and then laterally toward the 

temporal fossa (Figure 2.56C).

Remarks. Preliminary phylogenetic analyses based on 

the character-taxon matrix of Post et al. (2017) suggest a sister grouping of Cammackacetus hazenorum with Hadrodelphis 

calvertense. Future analyses including a larger number of early 

delphinidan taxa should allow for the testing of this hypothesis. 

More complete specimens of this presumably Late Miocene, robust delphinidan will help clarify its anatomy, paleoecology, and 

phylogenetic relationships.

Pictodelphis gen. nov.

FIGURES 2.57, 2.58

Here we describe another early delphinidan on the basis of 

a unique single partial skull.

Type and Only Included Species. Pictodelphis 

kidwellae.

Etymology. The generic name Pictodelphis honors 

David Rhea, who found the holotype, prepared it, and donated 

it to the CMM. The name comprises two parts. His family name, 

Rhea, was first used as a surname among the descendants of the 

ancient Scottish people known as the Picts, and delphis is dolphin in Greek. The “s” in “Picts” was changed to an “o” for ease 

of pronunciation.

Diagnosis of Genus. As for the type and only species.

Pictodelphis kidwellae sp. nov.

Holotype. CMM-V-8776, a partial skull (Figures 

2.57, 2.58, Table 2.8; postorbital width estimated at 144 mm) 

including the rostrum, part of the facial region, part of the right 

orbit, and the vertex, with several posterior maxillary teeth in 

situ and two teeth detached.

Etymology. Kidwellae was created in accordance 

with Article 31.1.2 of the ICZN by adding an “ae” to “Kidwell” 

to honor and recognize Susan M. Kidwell for her numerous publications on the geology of Calvert Cliffs (Kidwell, 1984, 1989, 

1997; Kidwell et al., 2015; Zimmt et al., 2022; among others).

Type Locality. North of Parkers Creek, Calvert 

Cliffs, Calvert County, Maryland.

Horizon and Age. SZ 11, Plum Point Member, 

Calvert Formation, Langhian (early Middle Miocene).

Known Range. SZ 11, Plum Point Member (Langhian) of the Calvert Formation.

Referred Material. None at this time.

Diagnosis of Species. Small delphinidan diagnosed by the following unique combination of characters: low 

cranial vertex; skull only slightly asymmetrical; maxillae and 

presphenoid form anterior margins of bony nares; posterolateral 

margin of premaxillae with lateral tuberosity, medial to which 

there is contact with nasals; dorsomedialmost margin of maxillae immediately adjacent to vertex overhangs lower more medially placed portion of maxillae that appears to “squeeze” the 

vertex bilaterally from below; in dorsal view, posterior margin 

of combined nasals approximates the shape of the letter W; lateral part of each nasal inflated; deep internasal basin on vertex, 

extending posteriorly on anterior portion of frontals on vertex; 

frontals wedge forward between nasals on vertex; deep fossa for 

preorbital lobe of pterygoid sinus nearly contacting the fossa for 

the postorbital lobe, dorsal to the frontal groove; premaxillary 

and anterior dorsal infraorbital foramina located in the area of 

the antorbital notch; antorbital maxillary tuberosity/ridge present (“dorsal swelling of maxilla” in Figure 2.57B); relatively 

elongate rostrum, narrow for its anterior half; rostrum length 

282 mm (antorbital notch to anterior extremity); 37 alveoli in 

left maxilla, possibly as many as 40 in right maxilla; 2 (possibly 3) alveoli per premaxilla; enamel crown of teeth conical 

and recurved; height of enamel crown to 6 mm; enamel base of 

crown to 3 mm in diameter; crown exhibits mesial and distal carinae (sometimes but rarely only weakly developed); distal carina 

often drawn out into accessory cusps, usually 2–4 along carina.
148 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.57. Pictodelphis kidwellae gen. et sp. nov. CMM-V-8776, holotype. (A) Partial skull in dorsal 

view. (B) Interpretive drawing of A. (C, D) Isolated upper teeth showing multiple cusplets. (C) Left upper #13. 

(D) Left upper #16. Scale bar for C and D equals 10 mm.
NUMBER 107 • 149

FIGURE 2.58. Pictodelphis kidwellae gen. et sp. nov. CMM-V-8776, holotype. (A) Ventral view of part of the 

skull. (B) Ventral view of a section of the rostrum. (C) Restoration of the skull in dorsal view. Scale bars for 

A and B equal 10 mm.
15 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Description. CMM-V-8776 consists of a partial 

skull lacking lower jaws (Figures 2.57, 2.58). Despite the fact 

that some of the cranial sutures are still partly open and several 

bones were detached (lacrimal, palatine), the following features 

evidence the osteological maturity of this small odontocete: presphenoid well ossified, the internarial portion of which forms 

a sharp-ridge apex; the midpoint in the dorsal exposure of the 

presphenoid coincides with the anterior margin of nares; and 

teeth present in well-defined circular alveoli, the enamel crowns 

of some of which exhibit significant tooth occlusal wear.

The condylobasal length of the skull is estimated to 420 mm. 

The skull appears to have been nearly symmetrical, and the nasals and frontals contribute equally to the height of the vertex 

(nasal slightly higher; see below). The vertex is low, rising only 

approximately 32 mm above the level of the horizontal dorsal 

margin of the rostrum.

Premaxilla. Anteriorly, the premaxillae border a 

dorsally open mesorostral canal. At about the midpoint in the 

length of the rostrum, the premaxillae abut or, in life, came very 

close to abutting along their dorsal midline margin. Posterior 

to this point, the mesorostral canal progressively opens until 

that space was filled with the midline-ossified portion of the 

presphenoid; the maximum opening is 9 mm anterior to the 

premaxillary foramen. The right premaxilla is slightly wider 

than the left in the posterior half of the rostrum. Just anterior 

to the presphenoid and posterior to the level of the antorbital 

notch, the dorsal surface of the premaxillae preserves the premaxillary foramina. The anteromedial sulcus is only partly preserved, and the surface of the prenarial triangle is damaged; the 

latter was still originally relatively elevated. From the premaxillary foramen, two shallow posterior troughs on each bone 

mark the anteromedial sulcus and the posterolateral sulcus, 

respectively. Posterior to the aforementioned foramen, the premaxillary sac fossa occupies the gently transversely and longitudinally concave dorsal surface of the premaxilla. A knob-like 

lateral projection is situated toward the posteriormost end of 

the premaxillae (adjacent to where they abut the nasals; Figure 

2.57B). Only the left premaxilla is preserved at its posterior 

apex, sending a thin posterior spine between the nasal and the 

maxilla, but not contacting the corresponding frontal. Marks 

of the suture of the right premaxilla on the maxilla indicate a 

roughly similar posterior extent.

Maxilla. The maxillae form the anteromedial margin 

of the external nares on either side of the presphenoid nasal 

septum (Figures 2.57A,B, 2.58C), making the anterior outline 

of the nares U shaped. More of the maxilla is exposed medial 

to the premaxillae than in any other odontocete, except for the 

monodontid Delphinapterus leucas (the beluga whale) (Lambert, pers. obs.). Posteromedial to the level of the antorbital 

notch, three small dorsal infraorbital foramina open on the 

dorsal face of each maxilla (Figs. 2.57A,B and 2.58C). Further forward, the dorsal surface of each maxilla is inflated in 

TABLE 2.8. Measurements of the holotype skull of Pictodelphis kidwellae gen. et sp. nov., 

CMM-V-8776. Symbols: asterisk (*) = estimated measurement.

Measurement

Dimension (mm)

Condylobasal length of the skull as preserved 400

Length of rostrum (antorbital notch to anterior extremity) 282

Length of anterior margin of supraoccipital to anterior margin of orbit 115*

Longitudinal distance between anterior margin of supraoccipital to 32* posterior edge of bony nares

Width of rostrum at its base (immediate antorbital width) 92

Maximum width of the premaxillae at the base of the rostrum 43

Height of rostrum at anterior maxillae 14

Width of the skull across the postorbital processes 2 × 72 = 144*

Length of orbit 40*

Width of rostrum at anterior end of maxilla 16

Width of premaxillae at rostrum base 41

Maximum width of left premaxillary sac fossa 25*

Width of bony nares 33

Width of nasals 30

Minimum distance between maxillae across the vertex 22

Least width of the skull across the supraorbital processes 2 × 68 = 136*
NUMBER 107 • 151

a dorsolateral direction immediately anterior to the antorbital 

notch. Along the frontal part of the vertex, the maxilla projects 

medially slightly beyond the level of the lateral margin of the 

bony nares. The vertex is thus somewhat pinched in its posterior part.

In lateral view, the tooth row bows ventrally throughout its 

length. The rostrum holds 42–44 well-formed alveoli per side 

(maxillary and premaxillary teeth combined). The transverse 

diameter of these tiny alveoli ranges from 4 to 4.5 mm, with 

interalveolar septa 1 to 1.5 mm long (Figure 2.58B). Right and 

left tooth rows are roughly parallel throughout the narrow anterior third of the rostrum, then gradually diverge posterolaterally, 

following the lateral margins of the broad-based rostrum. The 

last alveolus is about 25 mm from the corresponding antorbital 

notch. The palate is transversely convex but low, lacking any medial keel. The ventral surface of each maxilla is furrowed where 

it would have held the palatines.

Nasal. The nasals are roughly pentagonal in dorsal 

outline; each nasal is anteroposteriorly elongated, with the 

widest part located along the bony nares and the lateral margins converging slightly posteromedially. The anterior margin 

of each nasal is anteriorly concave, with a pointed anterolateral projection. The frontals wedge forward between the 

nasals, as a long (10 mm) and broad projection separating 

the nasals for one-third of their length. The lateral portion 

of each nasal is inflated, with a convex dorsal surface being 

higher than the frontal. A 10 mm deep midline trough, the 

internasal fossa (Figures 2.57B, 2.58A), forms an oval pit between the nasals and conjoined frontals. The floor of this pit 

descends posteriorly to a level anterior to the posterior end of 

the nasal before rising abruptly posterodorsally. In relation 

to the pinched aspect of the vertex, the frontals are narrower 

there than the nasals.

Frontal. The preserved right postorbital process of 

the frontal is nearly vertical and 24 mm long as measured from 

the edge of the frontal to its ventral tip. The incomplete preorbital process is barely thickened. The orbit is relatively short, 

with the length estimated to have been 45 mm. Ventrally, marks 

of the suture of the frontal with the lacrimal are conspicuous; the 

latter originally covered a large anteromedial part of the orbit 

roof. The infratemporal crest is acute. It is followed posteromedially by a fossa for the postorbital lobe of the pterygoid sinus. 

In addition, a deep fossa for the preorbital lobe of the pterygoid 

sinus is present on the frontal posterior to its suture with the 

lacrimal. Extending posterodorsally, this fossa deeply excavates 

the anteromedial part of the frontal groove and nearly contacts 

the fossa for the postorbital lobe dorsally to the narrow, residual 

medial portion of the frontal groove. At least within the cranial 

cavity, it would appear as though the supraoccipital wedged itself between the frontals.

Teeth. All the preserved teeth are small and conical, 

with a smooth enamel cap (Figure 2.57C,D). As in many other 

delphinidans, the crown of more posterior teeth is lower. At 

least some of the teeth from the posterior half of the rostrum 

display a string of bead-like cusplets (tiny accessory denticles) 

along a carina on their distal face (Figure 2.57D). The crowns 

of three adjacent teeth (#26–28) in the right maxilla are heavily worn along their entire mesial face; considering the short 

distance between successive teeth, these facets most likely correspond to attritional wear facets (occlusion with lower teeth; 

Figure 2.58B). The root is inflated immediately basal to the 

crown, and the root tapers proximally. The very thin proximal 

end of the tooth root terminates as a right-angle turn directed 

posteriorly (Figure 2.57C,D).

Remarks. The neurocranium of Pictodelphis kidwellae is close in size to that of Kentriodon pernix, and its rostrum is proportionally longer than that of Brevirostrodelphis 

dividum. In CMM-V-8776, the maximum width of the skull at 

the level of the postorbital processes is approximately 144 mm, 

whereas in K. pernix the roughly equivalent bizygomatic width 

is estimated to be 142 mm in USNM V 10670 (Kellogg, 1927a). 

In P. kidwellae, the breadth of the rostrum at the level of the 

antorbital notches is 91 mm; in K. pernix USNM V 8060, it is 

68 mm (breadth of the rostrum in P. kidwellae is approximately 

34% wider than in K. pernix, USNM V 8060). Pictodelphis 

kidwellae is slightly to moderately smaller than Westmorelandelphis tacheroni gen. et sp. nov., Kentriodon schneideri, 

Miminiacetus pappus, Rudicetus squalodontoides, and Tagicetus joneti and much smaller than Hadrodelphis calvertense and

Macrokentriodon morani. The unusual vertex of the skull of P. 

kidwellae is similar to the vertex of M. pappus, sharing with 

the latter anteroposteriorly elongated nasals, an inflated lateral 

part of each nasal, long anteromedial projection of frontals between nasals (best seen in USNM V 15985), a deep internasal 

fossa extending in the anterior part of the frontals, and the 

posterior part of the vertex being moderately pinched (with 

frontals being narrower than nasals). In addition, the two taxa 

share the dorsal surface of the maxilla being inflated anteromedial to the antorbital notch and a wide exposure of the maxilla 

along the anterior part of the bony nares. Despite these similarities, M. pappus is a much larger, more robust early delphinidan, characterized by a markedly lower tooth count (26 per 

row in USNM V 15985), larger teeth, and a deep constriction 

of the premaxillae at the rostrum base. Furthermore, no tiny 

accessory denticles are reported from the posterior teeth of M. 

pappus. Larger accessory denticles are described on the teeth of 

the early delphinidans B. dividum and Rudicetus squalodontoides (True, 1912; Bianucci, 2001).

In Pictodelphis, the length of the rostrum (antorbital notch 

to anterior extremity) is 282 mm, whereas in Kentriodon pernix, the length is 185 mm in USNM V 8060 and 199 mm in 

USNM V 10670. The rostrum in P. kidwellae is 40% longer 

than that in the largest known specimen of K. pernix (USNM 

V 10670).
15 2 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Westmorelandelphis gen. nov.

FIGURES 2.59, 2.60

Here we name a new genus and species of early delphinidan 

on the basis of a well-preserved skull.

Type and Only Included Species. Westmorelandelphis tacheroni.

Etymology. The generic epithet Westmorelandelphis

is derived from “Westmoreland,” the name of the county in the 

state of Virginia, USA, where the type specimen was found, in 

combination with delphis, “dolphin” in Greek.

Diagnosis of Genus. As for the type and only species.

Westmorelandelphis tacheroni sp. nov.

Holotype. USNM PAL 317882 (Figures 2.59, 2.60), 

a nearly complete skull (bizygomatic width = 166 mm; Table 

2.9) missing only the apex of the rostrum, with a mandible and 

ear bones. 

Type Locality. Nomini Cliffs, Westmoreland County, 

Virginia.

Horizon and Age. Nomini Cliffs consist of strata 

from the Miocene Choptank, St. Marys, and Eastover Formations and Pleistocene Bacon Castle Formation (Weems et al., 

2017). The lower half of the cliffs is made up of Choptank sediment with only a very narrow and laterally limited lens of the St. 

Marys Formation. The skull originated from the Choptank Formation, but unfortunately, we do not know from which SZ. The 

skull is listed here as Serravallian in age (late Middle Miocene).

Known Range. Choptank Formation (Serravallian).

Etymology. The specific epithet tacheroni honors 

Ben Tacheron, who found and donated this specimen to the 

USNM. Tacheroni was created in accordance with Article 31.1.2 

of the ICZN by adding an “i” to “Tacheron.”

Referred Material. None at this time.

Diagnosis of Species. This small delphinidan is 

characterized by the following unique combination of characters: elongated rostrum with a tooth count greater than 39 for 

each quadrant; transversely concave premaxillary sac fossae; 

vertex nearly 2 times wider than anteroposteriorly long; prominent posterolateral knob at posterior end of premaxilla; inflated 

nasals extending laterally significantly beyond the lateral margin of the bony nares; vertical notch on anterior margin of each 

nasal; internasal fossa; nasal-frontal suture posteriorly convex; 

inflated occipital shield being transversely convex; low temporal 

crest; temporal fossa being anteroposteriorly longer than dorsoventrally high, with a correspondingly moderately elongated 

zygomatic process of the squamosal; pterygoid sinus fossa extending anteriorly beyond the level of the antorbital notch; elongated mandibular symphysis being fused; postsymphyseal region 

of the mandible bearing 14 or 15 teeth per side; and small conical teeth lacking any ornamentation or accessory denticles.

Description. USNM PAL 317882 consists of a 

nearly complete skull, lacking only the anterior end of the rostrum (Figures 2.59, 2.60). Relatively minor postmortem dorsoventral crushing has distorted the cerebral portion of the skull. 

The skull is considered to have come from an adult individual 

because the alveoli are well-formed circular sockets with intervening septa. As preserved, the skull is 419 mm long, with a 

width of the rostrum at its base of 92.5 mm and a bizygomatic 

width of 166 mm. Although it is incomplete, the rostrum was 

elongated, with a narrow anterior portion and a tooth count 

greater than 39 for each upper tooth row. Compared to other 

early delphinidans, the vertex of the skull is only moderately 

elevated and transversely wide, being nearly 2 times wider than 

long (wider than in Brevirostrodelphis dividum, Kentriodon 

pernix, K. schneideri, Rudicetus squalodontoides, and Tagicetus joneti). The temporal fossa is anteroposteriorly longer than 

high (taking into account the fact that the neurocranium is 

somewhat dorsoventrally crushed).

Premaxilla. The rostrum presents an open mesorostral canal, which narrows in two places, at the midpoint in the 

length of the rostrum and then again medial to the premaxillary 

sac fossae (Figure 2.59A,C). Each premaxilla is slightly constricted a short distance anterior to the antorbital notch, with 

the right constriction being more developed. The premaxillary 

foramen (10 mm long on the right side of the skull) is just behind the level of the antorbital notch, followed anteriorly by the 

anteromedial sulcus. Medially, the prenarial triangle is slightly 

transversely concave, with a slight elevation of its medial margin. Although the posteromedial sulcus is barely defined, the 

posterolateral sulcus is visible until the posterior margin of the 

bony nares on the flank of a dorsoventrally thickened premaxillary sac fossa. Each fossa is slightly transversely concave, with 

an elevated medial margin and a convex lateral margin. Prominent posterolateral knobs characterize the premaxillae at the 

posterior margin of the nares. Each premaxilla displays a broad 

contact with the corresponding nasal but most likely did not 

reach the frontal.

Maxilla. The dorsal exposure of the maxilla is wider 

than the premaxilla at rostrum base, differing from B. dividum, 

K. pernix, and R. squalodontoides. Two main dorsal infraorbital foramina occupy the rostrum at the level of the antorbital 

notch. The antorbital notch is shallow and may have opened 

more laterally on the right side. The antorbital process of the 

maxilla is somewhat thickened, its dorsal surface making a low 

ridge higher than in B. dividum and K. pernix. A dorsal exposure of the maxilla is observed along the anterolateral margin of 

the bony nares, giving the nares an outline intermediate between 

U and V shaped. Along the vertex, the concave posteromedial 

part of the maxilla does not extend medially significantly beyond 

the level of the lateral margin of the nasal; the vertex is thus 

proportionally wider than in B. dividum and K. pernix. The posterolateral margin of each maxilla is angled, less rounded than 

in B. dividum.
NUMBER 107 • 15 3

FIGURE 2.59. Westmorelandelphis tacheroni gen. et sp. nov. USNM PAL 317882, holotype. (A) Skull in dorsal view. (B) 

Restoration of skull in dorsal view. The length of the rostrum is unknown. (C) USNM PAL 317882 in left ventrolateral view 

of the incompletely preserved anterior portion of the rostrum. Scale bar for C equals 10 mm.
15 4 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.60. Westmorelandelphis tacheroni gen. et sp. nov. USNM PAL 317882, holotype. (A) Skull in right dorsolateral 

view. (B) Skull in ventral view. Scale is for B.
NUMBER 107 • 15 5

Ventrally, the alveolar groove holds small alveoli (diameter 

ranging from 5 to 5.5 mm) with short (about 1 mm) interalveolar septa. The alveolar groove follows the lateral margin of the 

rostrum, except for the last four alveoli, which are slightly medially shifted. The palate is transversely convex, but not keeled.

Nasal. The nasals are inflated, more so than in D. dividum, K. hoepfneri, K. pernix, and R. squalodontoides, extending 

laterally beyond the lateral margins of the bony nares and forming 

the highest point of the vertex in a way more similar to Pithanodelphis cornutus, also with a deep internasal fossa. A vertical notch, 

defining an anterolateral projection (differing from R. squalodontoides), cuts the anterior margin of the nasal. Each nasal occupies a 

much larger portion of the vertex than the frontal (Figure 2.59A,C).

Frontal. The preorbital process of the frontal is thick 

and triangular in lateral view (Figure 2.60A). At mid-length of 

the orbit, the frontal becomes dorsoventrally thin, whereas the 

nearly vertical stiletto-like postorbital process of the frontal is 

29 mm long. In lateral view, the lacrimal is exposed as a thick 

strip of bone anteroventral to the preorbital process of the frontal. 

Ventrally, the infratemporal crest is high, followed posteriorly by 

a deep fossa for the postorbital lobe of the pterygoid sinus. The 

fossa for the preorbital lobe is also well developed in the lacrimal 

and frontal, being partly ventrally overhung by the narrow medial 

part of the frontal groove.

Supraoccipital. The nuchal crest is low, thin, and 

regularly anteriorly convex in dorsal view, lacking any anteromedial projection of the supraoccipital or interparietal between the 

maxillae (Figure 2.59). The occipital shield is smooth and inflated 

(transversely and dorsoventrally convex), with only a tiny external 

occipital crest along the posterior wall of the nuchal crest. The 

temporal crest was either low or not protruding posteriorly at all, 

as in many other small early delphinidans.

Squamosal. The zygomatic process of the squamosal 

is moderately elongated (distance from anterior tip to ventral end 

of postglenoid process = 54 mm on left side), shorter than in R. 

squalodontoides but longer than in K. pernix and T. joneti and 

more robust than in D. dividum, closer to K. schneideri. Its dorsoventral height increases distally, and its dorsal margin is concave. 

The postglenoid process is somewhat anteroposteriorly thickened 

in its lateral portion. The wide mandibular fossa covers ventrally 

part of the deep and wide (nearly as wide as the mandibular fossa) 

TABLE 2.9. Measurements of the holotype skull of Westmorelandelphis tacheroni gen. et sp. nov., 

USNM PAL 317882. Symbols: asterisk (*) = estimated measurement.

Measurement

Dimension (mm)

Length of skull as preserved 419

Width of rostrum at base 92.5

Width of premaxillae at rostrum base 45

Horizontal longitudinal distance between antorbital notch and supraoccipital 105

Preorbital width 152

Postorbital width 171.5

Width of right premaxillary sac fossa 28

Width of left premaxillary sac fossa 28

Maximum width of premaxillae on skull 70

Width of bony nares 36

Total width of nasals 52

Width of right nasal 25

Width of left nasal 27

Length of nasals 26*

Minimum distance between maxillae across vertex 47

Length of orbit 40

Length of temporal fossa 93*

Minimum distance between posterior margins of the temporal fossae (temporal crests) 86*

Width of occipital condyles 70

Height of occipital condyles 38.5

Width of foramen magnum 35
15 6 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

tympanosquamosal recess. The latter deeply excavates the medial 

wall of the postglenoid process. The supramastoid crest is sharp. 

The two deep fossae for the sternocephalicus muscle are located 

posterior to the level of the postglenoid process.

Palatine. The palatine-maxilla suture is difficult to 

follow on the palate, except for its posterolateral portion toward 

the ventral infraorbital foramen, where it converges with the 

maxilla-jugal suture (Figure 2.60B).

Pterygoid. The length of the pterygoid sinus fossa 

(Figure 2.60B) anterior to the level of the antorbital notches is 

25 mm, considerably longer than in B. dividum, K. schneideri, 

and R. squalodontoides. The lateral lamina of the palatine (and 

possibly part of the pterygoid) is preserved to the level of the 

frontal groove.

Jugal. The jugal is not fused to the lacrimal, its outline 

being well defined posteromedial to the antorbital notch. The 

outer margin of the ventral infraorbital foramen is formed by 

the lacrimal.

Basioccipital. The basioccipital crest remains transversely concave throughout its length (Figure 2.60B). Posteriorly, its medial surface bears a ridge that passes anterodorsally 

toward the floor of the basioccipital basin.

Exoccipital. The anterior wall of the paroccipital process is excavated by a wide groove, whereas ventrolaterally on 

the anterior surface of the exoccipital, a deeper, transversely narrow and dorsomedially directed fossa most likely corresponds 

to a fossa for the posterior sinus. The hypoglossal foramen is 

posteromedial to the jugular notch.

Mandibles. USNM PAL 317882 also preserves incomplete mandibles (missing only the apex) that include at least 38 

circular and well-formed alveoli on each side, more than 23 in 

the symphyseal region and 14/15 in the left/right postsymphyseal 

region. The mandible is slender, with a fused, elongated symphysis (more than 137 mm long) and a low coronoid process. The 

height and width of the fused mandibles at the posterior end of 

the symphysis are 22 and 29 mm, respectively.

Teeth. Teeth possess medially curved conical crowns 

(Figure 2.59C). Posterior tooth crown height is 8 mm. The 

mesiodistal length of the base of the crown is 4.7 mm. The labiolingual width of the base of the enamel crown is 5.2 mm. 

Mid-rostrum crown height is 8.7 mm. Teeth form curved cones, 

lacking any noticeable development of a carina or accessory denticles on the crown.

Superfamily Inioidea Gray, 1846

Family Pontoporiidae Kasuya, 1973

Pontoporiidae is represented today by only one relict 

species, the Franciscana or La Plata dolphin, Pontoporia blainvillei (Gervais and d’Orbigny, 1844), a small, near-shore 

odontocete that lives in the eastern coastal waters of Brazil, 

Uruguay, and Argentina (Crespo, 2002; Secchi, 2010) and in 

the La Plata River and Babitonga Bay estuaries (Cremer and 

Simões-Lopes, 2005; Secchi, 2010). Contrary to the impression their current geographic limitations would give, a number of extinct genera, from the Tortonian to the Zanclean, are 

known from the eastern Pacific Ocean and the North Atlantic 

Ocean (Post et al., 2017; Lambert et al., 2020). The family 

first appears in the fossil record in the early Late Miocene. 

Pontoporiids are represented along Calvert Cliffs by only the 

type specimen (CMM-V-2234) of one species, Stenasodelphis russellae Godfrey and Barnes, 2008. Because the skull 

is only partially preserved and the ear bones are not known, 

there has been volatility in its placement within the Inioidea 

in recent phylogenetic analyses. It would be beneficial to find 

more complete representatives of this poorly known Tortonian odontocete.

Stenasodelphis russellae Godfrey and Barnes, 2008

FIGURE 2.61

Stenasodelphis russellae – Pontoporiidae

(Illustration by Brenna Litynski)

Holotype. CMM-V-2234 (Figure 2.61), the facial region of a skull with the base of the rostrum, collected in November 2000 by the late Jean Hooper (née Russell). 

Type Locality. The holotype was recovered from the 

base of a slump pile approximately 800 m north of Seahorse 

Beach, Calvert County, Maryland.

Horizon and Age. Although Stenasodelphis russellae was not found in situ, much of it was encased in gray clay 

that is typical of SZ 22 and 23 of the Little Cove Point Member 

of the St. Marys Formation. These beds are Late Miocene in age 

(Tortonian), 9–10 Ma.

Known Range. SZ 22–23, Little Cove Point Member 

(Tortonian) of the St. Marys Formation.

Referred Material. None at this time.

Diagnosis of Species. Diagnostic characters of 

Stenasodelphis russellae can be found in Godfrey and Barnes 

(2008).

Remarks. Godfrey and Barnes (2008) described the 

holotype skull, and that description need not be repeated here. 

Phylogenetic analyses recovered Stenasodelphis russellae as most 
NUMBER 107 • 157

closely related to Auroracetus bakerae (Gibson and Geisler, 

2009; Geisler et al., 2012; Pyenson et al., 2015), an Early Pliocene pontoporiid from the Yorktown Formation in the Aurora 

Phosphate Mine. Auroracetus bakerae is currently the only other 

named pontoporiid from North America (other pontoporiid 

periotics are known from that quarry [Whitmore, 1994; Whitmore and Kaltenbach, 2008] and from the Bone Valley Member of the Peace River Formation in Florida [Morgan, 1994]; 

see also Lambert et al., 2020, for the tentative identification of 

Meherrinia isoni, from the Late Miocene of North Carolina, as a 

pontoporiid). Among living delphinidans, the La Plata dolphin 

(Pontoporia blainvillei) is most closely related to the Amazon 

River dolphin (Inia geoffrensis, Iniidae), and together they comprise the superfamily Inioidea. Although both are indigenous to 

South America, the fact that Stenasodelphis russellae is one of the 

oldest known pontoporiids opens the possibility that the Inioidea did not originate in South America. Post et al. (2017) report 

that the oldest inioids were thought to have originated in the late 

Middle Miocene (Serravallian) off the west coast of South America. However, revised ages for several Pisco Formation inioids 

FIGURE 2.61. Stenasodelphis russellae. CMM-V-2234, holotype. (A) Facial region of skull in dorsal view. (B) Interpretive drawing of A. 

(C) Right lateral view. Specimen whitened with sublimed ammonium chloride. (A, B) Images modified from Godfrey (2008).
15 8 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

(the pontoporiid Brachydelphis mazeasi and the iniid Brujadelphis ankylorostris) may mean that they are not significantly 

older than some of the inioids from the North Atlantic (Bianucci 

et al., 2016b; Bosio et al., 2020b). Considering the number of 

Late Miocene taxa in the North Atlantic, this region must have 

been an important center of diversification for inioids during the 

Late Miocene (Post et al., 2017).

Odontoceti Incertae Sedis

Caolodelphis gen. nov.

FIGURES 2.62, 2.63

A single partial skull (Figures 2.62, 2.63) found low in the 

Calvert Formation along the Potomac River could not be identified as belonging to any of the named odontocetes known from 

within the Chesapeake Group. However, it does share some similarities with Chilcacetus cavirhinus and related, but more fragmentarily known, forms (“Argyrocetus” bakersfieldensis, “A.” 

joaquinensis, and Macrodelphinus), all of which derive from the 

Early Miocene east Pacific (Kellogg, 1932; Wilson, 1935; Lambert et al., 2015b). Unfortunately, the only specimen of Caolodelphis milleri currently known does not preserve some parts of 

the skull and, consequently, not all the diagnostic features of 

this yet unnamed clade of longirostrine homodont odontocetes. 

Nevertheless, this specimen (CMM-V-9849) is sufficiently well 

preserved, and it exhibits several autapomorphic features that 

enable us to give it a new generic and specific name.

Type and Only Included Species. Caolodelphis 

milleri.

Etymology. The generic epithet Caolodelphis honors 

Kyle Grimsley, who found, prepared, and donated the specimen to the CMM. The name Caolodelphis is a combination of 

caol, the Gaelic root of “Kyle” (meaning a narrows, a strait, or 

a sound, a serendipitous reference to water), and delphis, “dolphin” in Greek.

Diagnosis of Genus. As for the type and only species.

Caolodelphis milleri sp. nov.

Holotype. CMM-V-8949 (Figures 2.62, 2.63), a partial skull preserving most of the neurocranium from the supraorbital region to the occipital condyles. The rostrum, periotics, and 

tympanic bullae were not preserved. The neurocranium suffered 

mild dorsoventral compression.

Type Locality. Found approximately 3.4 m up in the 

cliff along the Potomac River at Popes Creek, Charles County, 

Maryland.

Horizon and Age. It was found low in the Popes 

Creek Sand (Fairhaven Member, Calvert Formation, Burdigalian, Early Miocene), approximately 30 cm above the contact 

with the Eocene Nanjemoy Formation.

Known Range. Popes Creek Sand, Fairhaven Member (Burdigalian) of the Calvert Formation.

Etymology. Milleri was created in accordance with 

Article 31.1.2 of the ICZN by adding an “i” to “Miller,” which 

honors the late Thomas V. “Mike” Miller Jr., a long-time Maryland state senator and former Senate president, for his support 

of paleontology.

Referred Material. None at this time.

Diagnosis of Species. Medium-size odontocete 

with the following unique combination of characters: postorbital 

width of skull approximately 230 mm; flattened frontals on the 

vertex; left and right frontals on the vertex separated from one 

another (possibly exaggerated to some extent by taphonomic 

processes); anterior end of the zygomatic processes drawn out 

into a pointed spur; and the basioccipital crests being greatly 

thickened transversely (the latter two probably represent autapomorphic features). This new odontocete further differs from 

most other clades of odontocetes except Eoplatanista, eurhinodelphinids, squaloziphiids, and members of the Chilcacetus clade 

in the anteroposteriorly thick postglenoid process, from Platanidelphidi in the posterior dorsal infraorbital foramen being located lateral to the lateral margin of the premaxilla, and from 

eurhinodelphinids in the occipital shield projecting farther anteriorly and the temporal fossa being dorsoventrally higher and 

more broadly open posterodorsally. The maximum width of the 

skull (i.e., the bizygomatic width) is less than in Chilcacetus cavirhinus, much less than in Macrodelphinus kelloggi, and greater 

than in “Argyrocetus” joaquinensis and Eoplatanista spp.

Description. CMM-V-8949 was from a medium-sized 

odontocete with a postorbital width of 231 mm, a bizygomatic 

width of 235 mm, and a bicondylar width of 98 mm. The sutures between the bones are, for the most part, closed, suggesting a mature individual. However, the premaxilla adjacent to the 

right naris is no longer attached to the maxilla, and there is wide 

separation between the right and left frontals on the vertex. The 

braincase is slightly dorsoventrally crushed, as indicated by cracks 

in the supraoccipital and displacement of bone along the temporal crest. The skull is as wide as it is long, with a vertex that is 

only weakly elevated (Figure 2.63). The posterolateral edge of the 

frontal opposite the level of the supraoccipital is slightly sigmoidal 

and oblique (posteromedially) in dorsal view. Consequently, the 

dorsal and lateral surfaces of the zygomatic process of the squamosal are visible in dorsal view (Figure 2.62A). As in Chilcacetus

(Lambert et al., 2015a), the facial region of the skull is roughly 

trapezoidal in outline. Despite the mild dorsoventral compression, 

the skull appears as though it was symmetrical about the midline. 

In CMM-V-8949, the temporal fossa is dorsoventrally higher than 

in the Calvert eurhinodelphinids Schizodelphis and Xiphiacetus, 

and the telescoping of the skull is not as developed as in eurhinodelphinids, as evidenced by the long anteroposterior extent of the 

occipital shield in dorsal view.

Premaxilla. The premaxillae are not preserved; nevertheless, there is a trough on the dorsal surface of the right maxilla (Figures 2.62A, 2.63) that would have held the premaxillary 
NUMBER 107 • 15 9

FIGURE 2.62. Caolodelphis milleri gen. et sp. nov. CMM-V-8949, holotype. Neurocranium in (A) dorsal and (B) ventral 

views, respectively.
160 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

sac fossa and ascending process of the right premaxilla. It would 

appear from the markings on the maxilla that the premaxilla 

reached back to the anterior margin of the frontal on the vertex.

Maxilla. The supraorbital and ascending portions 

of the maxillae are preserved in CMM-V-8949. Anteriorly, on 

the right side of the skull, a single large anteromedially passing 

trough comprises part of the anterior dorsal infraorbital foramen. Posteromedially, the maxillae turn dorsally to present a 

vertical face, the medial side of which abuts the frontals on the 

vertex. Ventrolaterally, a small posterior dorsal infraorbital foramen is visible on the right maxilla, lateral to the lateralmost 

level of the premaxilla-maxilla suture. Such a position differs 

from platanistids and squalodelphinids, in which the foramen is 

more medially located. In dorsal view, the lateral, posterolateral, 

and posterior margins of the maxilla on the neurocranium are 

framed by the frontal. A band of the frontal, approximately 10 

mm wide, separates the maxilla from the supraoccipital.

Frontal. In dorsal view, the shape of the left frontal on 

the vertex is roughly triangular, whereas the contralateral frontal 

is roughly quadrilateral. The frontals are widely separated on 

the vertex, but we think that at least some of this separation is 

due to erosion of the original size of the frontals and/or separation of the bones due to the slight postmortem dorsoventral 

compression of the skull. On the vertex, each frontal appears 

to have been as long as wide. The dorsal surface of each frontal 

slopes anteroventrally. In the absence of the nasals, the complex 

shape of the frontals below their dorsal exposure is visible in an 

anterior view of the skull. Posterior to the orbit, the triangular 

postorbital process of the frontal is approximately 30 mm long 

in the vertical axis.

In ventral view (Figure 2.62B), most of the orbital surface of 

the frontal is featureless. Posteriorly, the infratemporal crest (i.e., 

the postorbital ridge) is not sharply defined such that there is 

poor separation between the orbital and temporal regions of the 

frontal. The infratemporal crest marks the posterior margin of 

FIGURE 2.63. Caolodelphis milleri gen. et sp. nov. CMM-V-8949, holotype. Neurocranium in right dorsolateral view. Note that in this 

view, both frontals on the vertex are visible, as are both occipital condyles.
NUMBER 107 • 161

the frontal groove, which is angled posteromedially. As in Chilcacetus, there is no indication that the pterygoid sinus invaded 

the temporal and/or orbital region of the frontals in CMM-V8949, a difference from eurhinodelphinids Schizodelphis and 

Xiphiacetus (Lambert, 2005a).

Supraoccipital. In dorsal view (Figure 2.62A), the 

supraoccipital gains broad exposure, somewhat exaggerated 

by dorsoventral compression of the skull. Although widely exposed, the lateral reach of the supraoccipital does not preclude 

exposure in a dorsal view of the floor of the temporal fossa (i.e., 

squamosal fossa) medial to the supramastoid crest on the dorsomedial surface of the zygomatic process of each squamosal. 

Dorsally, the nuchal crest is not elevated above the level of the 

frontals. Below the nuchal crest are two bilaterally symmetrical 

depressions (recesses) that might mark the origin of neck muscles 

(possibly the semispinalis or rhomboideus muscle). In posterior 

view, the minimum distance between temporal fossae across the 

occipital shield is located close to the top of the temporal fossae.

Vomer. The vomer is preserved only in ventral view (Figure 2.62B), forming the keel between the choanae and expanding 

posteriorly into a plate that underlapped the basisphenoid.

Squamosal. The complete anterior margin of the zygomatic process tapers abruptly to an acute point just posterior 

to the postorbital process of the frontal and about 32 mm anterior to the point at which the subtemporal crest turns into the 

zygomatic process (Figure 2.62B). In dorsal view, the floor of the 

squamosal fossa is transversely and longitudinally concave. Posterolateral to the squamosal fossa, the deep and coarsely ridged 

sternocephalicus fossa is bound posteriorly by the vertical anterolateral face of the exoccipital.

The mandibular fossa is about 30 mm wide at the midpoint 

in its length. Throughout its length, it faces anteroventrally and 

only very slightly medially. Posteriorly, the anteroposteriorly 

thickened postglenoid process is reminiscent of the condition 

seen in eurhinodelphinids, Eoplatanista, and the “Chilcacetus

clade” but is not as thick as in squaloziphiids (Lambert et al., 

2019). In ventral view, this process is approximately as long as 

it is wide. The medially directed spiny process is located immediately above and behind the postglenoid process. The rounded 

medial edge of the mandibular fossa separates the fossa from the 

18 mm-wide tympanosquamosal recess (Figure 2.62B). Medial 

to the midpoint in the length of the tympanosquamosal recess, 

the flange of bone comprising the falciform process of the squamosal projects anteroventromedially.

Exoccipital. The occipital condyles are very wide but 

have almost no development of a condylar neck. There is only a 

weakly developed dorsal condyloid fossa. The paroccipital processes are very well developed, with an anteroposterior thickness 

of 21 mm just lateral to the deep jugular notch.

Basioccipital. In a ventral view of the skull (Figure 

2.62B), the posterolateral arms of the pterygoids (=pharyngeal 

crests) that onlapped the anterolateral surfaces of the basioccipital are not preserved. The basioccipital crests are greatly thickened transversely, reaching a maximum thickness of 25 mm at 

about their midpoint in length. In ventral view, these crests are 

so thickened that the ventrolateral edge of the crest does not obscure the lateral face of the crest as in other odontocetes. Rather, 

the lateral face of the crest bulges out toward the periotic fossa, 

a condition not observed in Chilcacetus cavirhinus and “Argyrocetus” joaquinensis. These thickened crests diverge posterolaterally from one another to form an angle of about 55°. The 

transversely concave basioccipital basin is smooth and generally 

featureless. Posterolaterally, the basioccipital crests present a 

nearly horizontal ventral surface, the medial and posterior margin of which may have held the origin of cervical musculature.

Enigmatocetus gen. nov.

FIGURES 2.64–2.66

Here we describe the partial skeleton of a highly unusual 

odontocete that, at present, defies placement within any odontocete clade.

Type and Only Included Species. Enigmatocetus 

posidoni.

Etymology. From “enigma,” a deep mystery or puzzle, plus ketos, Greek for a large sea animal or whale, here using 

the Latin form of the noun, cetus. The “o” in Enigmatocetus was 

added for ease of articulation.

Diagnosis of Genus. As for the type and only species.

Enigmatocetus posidoni sp. nov.

Holotype. USNM PAL 244524 (Figures 2.64–2.66), 

a fragmentary skull including part of the right supraorbital region, right and left squamosal regions, right and left periotics 

and tympanic bullae, basioccipital and exoccipitals, and six thoracic vertebrae. 

Type Locality. Cliff close to George Washington 

Birthplace National Monument, Westmoreland County, Virginia.

Horizon and Age. Plum Point Member (base of SZ 

10) of the Calvert Formation, Chesapeake Group, Middle Miocene.

Known Range. SZ 10 (Langhian), Calvert Formation.

Etymology. The specific epithet posidoni is taken in 

part from “Siddons” and honors Derek Siddons, who found the 

type specimen. The surname was altered by adding the prefix 

“po” and removing one “d” and the final “s,” so that it became 

“posidon,” a homophone of Poseidon, the violent and ill-tempered Greek god of the sea. Posidoni was created in accordance 

with Article 31.1.2 of the ICZN by adding an “i” to “posidon.”

Referred Material. USNM PAL 534007, an isolated periotic found as float on the beach 125 m south of the 

stairs to the beach at Chestnut Cabin, Scientists Cliffs, Port Republic, Calvert Cliffs, Calvert County, Maryland.

Diagnosis of Species. A small odontocete characterized by a series of highly autapomorphic features: anteroposteriorly long postglenoid process being projected far anteriorly and 
162 

FIGURE 2.64. Enigmatocetus posidoni gen. et sp. nov. USNM PAL 244524, holotype. (A–E) Partial skull, disarticulated, ventral view. (A) Right frontal. (B) Right frontal mirrored to resemble the left frontal in ventral view. (C) Partial 

right squamosal with periotic in situ. (D) Partial left squamosal with periotic and bulla in situ. (E) Basioccipital and exoccipitals in ventral view. (F) Occipital and exoccipitals in dorsal view. (G) Right frontal in lateral view. (H) Right frontal 

in dorsal view. (I) Right partial squamosal in lateral view. Specimen whitened with sublimed ammonium chloride. 
making the ventral margin of the squamosal highly concave in 

lateral view; posterior process of periotic being broadly expanded 

posterodorsally and being exposed on the outer surface of the basicranium between squamosal and exoccipital; broad facial sulcus along the whole medial surface of the posterior process of the 

periotic; markedly reduced involucrum of the tympanic bulla in 

both lateral and ventral views; depressed area on dorsal margin 

of involucrum for the accessory ossicle; voluminous sigmoid process of the tympanic bulla directed anteromedially in dorsal view; 

greatly inflated accessory ossicle of the tympanic bulla being anteriorly as long as the anterior process of the periotic; and lateral 

and medial margins of the posterior process of the tympanic bulla 

wrapping around the lateral and medial margins of the posterior 

process of the periotic. It further differs from other odontocetes in 

the following unique combination of characters: dorsal margin of 

the zygomatic process of the squamosal being markedly convex; 

extremely deep posterior part of the tympanosquamosal recess; tip 

of anterior process of periotic being slender and pointed; anterior 

bullar facet being present; endocranial opening of the facial canal 

being lateral to the spiral cribriform tract; suprameatal fossa being 

well defined on the periotic; absence of a lateral furrow on the 

tympanic bulla; and tubercule of the malleus being longer than 

the head.

Description. The four main cranial elements of 

USNM PAL 244524 (right supraorbital region, right and left 

squamosal regions, and basioccipital plus exoccipitals) are detached, but the left squamosal can be approximately placed into 

contact with the corresponding exoccipital; each periotic matches 

perfectly the corresponding tympanic bulla, and the periotics can 

be precisely articulated with the squamosals.

Frontal. Only the frontal is preserved in the right 

supraorbital region (Figure 2.64). The preorbital process is 

moderately thickened; the roof of the orbit (54 mm long) is 

deeply concave, and the postorbital process is short (17 mm), robust, and triangular in lateral view. Suture marks on the slightly 

arched (in lateral view) dorsal surface of the fragment indicate 

that the maxilla originally nearly completely covered the frontal 

in this region, except for the anterolateralmost portion. Posterior 

to the level of the postorbital process, the posteromedial part of 

the frontal rises abruptly, probably toward the nuchal crest. This 

suggests a relatively short (about 113 mm from the tip of the 

preorbital process to the posterior end) facial region. Compared 

to the lateral margin of the orbit, the frontal groove is oblique in 

ventral view and posteriorly margined by a distinct infratemporal crest. No fossa for an orbital lobe of the pterygoid sinus was 

found, differing from some platanistids and squalodelphinids 

(Lambert et al., 2014; Boersma et al., 2017). A fragment of the 

orbitosphenoid is possibly preserved on the posteromedial wall 

of the frontal groove.

Squamosal. Each squamosal has a unique shape in 

lateral view, with an anteriorly short zygomatic process, an anteroposteriorly long postglenoid process (to an extent seen in 

only Squaloziphius emlongi; Muizon, 1991), a highly convex 

dorsal margin, and a correspondingly highly concave ventral 

margin (Figures 2.64, 2.65). Consequently, the mandibular fossa 

is markedly anteroposteriorly shortened compared to those of 

other odontocetes. Although the anterior part of the tympanosquamosal recess is moderately excavated anteromedial to the 

mandibular fossa, the posterior half of the recess is much more 

excavated, resulting in a deep fossa extending dorsally and laterally at the base of the postglenoid process. Such a depth of 

the tympanosquamosal recess is, to our knowledge, observed in 

only the extant Platanista (e.g., USNM PAL 172409). The falciform process is partly preserved on both sides. When placing 

FIGURE 2.65. Enigmatocetus posidoni gen. et sp. nov. USNM PAL 244524, holotype. (A) Left partial squamosal with periotic in situ in 

posterolateral view. Left partial squamosal with periotic (B) in situ and (C) removed in ventromedial view. Specimen whitened with sublimed 

ammonium chloride.

 NUMBER 107 • 163
16 4 

FIGURE 2.66. Enigmatocetus posidoni gen. et sp. nov. USNM PAL 244524, holotype. (A, C, D) Right periotic in medial, 

dorsal, and ventral views, respectively, lacking the large accessory ossicle. (B) Left periotic in ventral view, with the large 

accessory ossicle attached. (E–H) Left tympanic bulla in dorsal, ventral, medial, and lateral views, respectively. (I) The 

right malleus and incus are articulated one to the other, still attached to the outer lip of the corresponding tympanic bulla. 

Specimen whitened with sublimed ammonium chloride. Scale bars for D–I equal 10 mm.
NUMBER 107 • 165

the periotic in situ (Figures 2.64, 2.65), the lateral margin of 

the periotic does not follow the posteromedial margin of the 

falciform process, diverging more ventrally (and differing thus 

from the more conservative condition seen, for example, in platanistids). The medial part of the postmeatal crest is excavated 

by a deep and narrow fossa for the anterolateral margin of the 

posterior process of the tympanic bulla. Posterior to the postmeatal crest, a deep and wide notch, opening posterolaterally 

between the ventral surface of the reduced posttympanic process 

(6 mm thick) and the ventrolateral margin of the exoccipital, receives the posterior process of the periotic. The latter is thus exposed on the posterolateral surface of the neurocranium (Figure 

2.65A), a feature unknown in other odontocetes (the enlarged 

posterior process of the tympanic bulla is exposed in at least 

some physeteroids and ziphiids). Dorsal to the notch, a small 

fossa for the sternocephalicus muscle is located below the thin 

supramastoid crest.

Basioccipital. The transversely wide basioccipital 

basin is shallow, being defined by low, ventrolaterally directed 

basioccipital crests (Figure 2.64E,F).

Periotic. That an identifiable periotic from a second 

individual is known (USNM PAL 534007) adds considerable 

weight to our claim that the enigmatic morphology of the type 

specimen is not the result of widespread pathology. In the type 

(USNM PAL 244524), both periotics are complete, each with a 

total length of 45 mm (Figure 2.66A–D). The anterior process is 

short (9 and 8.5 mm for left and right bones, respectively) and 

pointed, with a slender apical region. The anterior bullar facet is 

short and narrow but markedly transversely concave, a condition reminiscent of physeteroids. Posterior to the anterior bullar facet, each periotic retains a fragment of the outer lip of the 

tympanic bulla, whereas the voluminous accessory ossicle is preserved on only the left periotic (Figure 2.68B), between the facet 

and the pars cochlearis (see below). On its dorsomedial side, the 

base of the anterior process bears a tuberosity. In dorsal view, a 

narrow groove directed laterally, before turning posterolaterally, 

separates the anterior process from the pars cochlearis of each 

periotic. The lateral tuberosity is short. The mallear fossa is large 

(maximum diameter = 5.2 mm on right side) and faces ventrally. 

There is no submallear fossa (sensu Tanaka and Fordyce, 2017). 

The hiatus epitympanicus is deep and broadly open.

The posterior process is long (18.4 and 22.1 mm long from 

anterior to posterior tips of posterior bullar facet for the left and 

right bones, respectively). The platelike posterior bullar facet is 

slightly transversely convex, and it turns only slightly posteroventrally. This facet contributes only a small part to the posterior process, which is greatly expanded posterodorsally, forming 

a large blade whose lateral/medial surface broadens distally. 

Whereas the lateral surface is transversely convex, the medial 

surface is highly concave, forming a broad groove that is strikingly similar to the facial sulcus extending along the compound 

posterior process of the tympanoperiotic in part of the mysticetes (see character 182 in Marx and Fordyce, 2015). The dorsal 

margin of the posterior process corresponds to the dorsal edge 

of this large blade; it thickens somewhat posterolaterally and extends posteriorly roughly to the same level as the posteroventral 

corner of the posterior process. Such a shape of the posterior 

process is unique among odontocetes. Along the anterolateral 

wall of the posterior process, no articular process or articular 

rim was detected.

In ventral view, the outline of the pars cochlearis is rounded. 

Its anterior wall draws an angle of about 90° with the medial 

margin of the anterior process. The reniform fenestra rotunda 

displays a notch extending mediodorsally toward the aperture 

for the cochlear duct. Located on the dorsomedial surface of 

the pars cochlearis, the latter is subcircular and smaller than the 

aperture for the endolymphatic duct, which is also subcircular 

and as close to the internal acoustic meatus as the aperture for 

the cochlear duct. The internal acoustic meatus is oval, with 

the endocranial opening of the facial canal being lateral to the 

spiral cribriform tract. The foramen singulare is separated by 

a slightly more developed crest from the latter than from the 

opening of the facial canal. Lateral to the internal acoustic meatus, the surface of the bone is smoothly concave, corresponding to a suprameatal fossa shallower than in xenorophids (e.g., 

Albertocetus; Uhen, 2008b). A curved dorsal crest defines the 

suprameatal fossa laterally.

Tympanic Bulla. In ventral view, the outer posterior prominence is much wider than the inner prominence, and 

it is separated from the latter by a deep interprominential notch 

(Figure 2.66). From the narrow and posteromedially protruding inner prominence, the medial margin of the tympanic bulla 

turns anterolaterally before becoming parallel to the long axis 

of the bone. Corresponding to a transversely narrow anterior 

part of the involucrum, such a constriction of the medial margin in ventral view is, to our knowledge, unknown in other 

odontocetes (more developed than in Platanista). The median 

furrow is shallow and narrow but distinct until about threequarters of the length of the tympanic bulla. There is no anterior spine. In medial view, the ventral margin of the bone 

is slightly concave. Being moderately elevated posteriorly, the 

dorsal margin of the involucrum descends gradually for a short 

distance before a marked step as seen in eurhinodelphinids. 

This depressed, intermediary part of the dorsal margin corresponds to the surface of contact with the enlarged accessory 

ossicle, whereas in many odontocetes (including physeteroids 

and Platanista) a depressed region of the dorsal margin of the 

involucrum houses the pars cochlearis. From mid-length, this 

dorsal margin rises slightly before the final gradual descent toward the anterior apex of the bone.

In lateral view, the ventral margin of the tympanic bulla is 

slightly concave. The outer lip is moderately elevated anterodorsally (less than in platanistids) but extends far medially, nearly 

closing the tympanic cavity in dorsal view. There is no lateral 

furrow. A very large left accessory ossicle is preserved attached 

to the corresponding periotic, ventrally prominent and extending anteriorly as much as the anterior process of the periotic—

a condition unseen in any other odontocete.
166 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

In dorsal view, the sigmoid process is markedly inflated and 

directed anteromedially (contrasting with the transversely directed sigmoid process in other odontocetes). The posterior process is dorsoventrally thick. Both its lateral and medial margins 

send a lamina that wraps around the corresponding margins of 

the posterior process of the periotic.

Malleus and Incus. The right malleus and incus 

are articulated one to the other, still attached to the outer lip of 

the corresponding tympanic bulla (Figure 2.66I). On the malleus, the articulation facets for the incus occupy less than half 

the height of the bone. The pointed manubrium is roughly at the 

same level as the muscular process on the apex of the tubercule.

Thoracic Vertebrae. The preserved thoracic vertebrae of USNM PAL 244525 differ only in size from the thoracics of the squalodelphinid Huaridelphis raimondii and the 

pomatodelphinine Zarhachis flagellator (see Kellogg, 1924a; 

Lambert et al., 2014).

Remarks. Considering the marks of the suture for the 

overlying lost maxilla on the dorsal surface of the supraorbital 

process of the frontal and the presence of a distinct tympanosquamosal recess (Fraser and Purves, 1960), Enigmatocetus posidoni

(USNM PAL 244525) is undoubtedly an odontocete. However, 

the specimen displays a series of morphological features that we do 

not observe (at least to the same extent) in any other odontocete:

• The ventral margin of the zygomatic process of the squamosal is more concave than in any other odontocete because of the anteroposteriorly long postglenoid process 

projecting far anteriorly. Although the postglenoid process 

of the latest Oligocene to Early Miocene squaloziphiids 

Squaloziphius emlongi and Yaquinacetus meadi is anteroposteriorly long, it does not project as far, leaving thus a 

more open mandibular fossa (Lambert et al., 2019).

• The posterior process of the periotic is markedly expanded posterodorsally, and its medial surface is occupied by a broad facial sulcus. With the periotic in situ in 

the basicranium, this process is exposed on the posterolateral surface of the skull, a condition unknown in other 

odontocetes, including the early branching xenorophid 

Echovenator sandersi (Churchill et al., 2016: fig. 2) and 

the simocetid Simocetus rayi (Fordyce, 2002).

• The involucrum of the tympanic bulla is greatly reduced, 

both in the height of its anterior part in medial view and 

in its transverse width in ventral view. The volume of the 

involucrum is reduced in some extant delphinoids, for example, Monodon monoceros, in both medial and ventral 

views and in Platanista gangetica in ventral view (Kasuya, 

1973; see also below), but not to the extent seen in Enigmatocetus posidoni.

• Contrasting with the reduced involucrum, the sigmoid 

process of the tympanic bulla is surprisingly voluminous 

and directed anteromedially in dorsal view, contrasting 

with the more slender, transversely directed process in 

other odontocetes.

• The accessory ossicle of the tympanic bulla is greatly inflated, and it is as long anteriorly as the anterior process 

of the periotic.

• The lateral and medial margins of the posterior process 

of the tympanic bulla wrap around the lateral and medial 

margins of the posterior process of the periotic.

Despite this list of presumably autapomorphic features, 

Enigmatocetus posidoni shares some characters with two odontocete clades:

• First, it shares with physeteroids an enlarged accessory ossicle, a narrow and pointed anterior bullar facet of the periotic, and the endocranial opening of the facial canal being 

lateral to the spiral cribriform tract (see Lambert et al., 

2017a). However, among other differences (e.g., the shape 

of the squamosal), the tubercule of its malleus is proportionally much longer (see Bianucci et al., 2010), and its tympanic 

bulla differs markedly from the physeteroid morphotype, for 

example, in the presence of a long median furrow.

• Second, Enigmatocetus posidoni (USNM PAL 244525) 

shares with platanistids and squalodelphinids (or part 

of them) a voluminous zygomatic process of the squamosal, with a highly convex dorsal margin in lateral 

view; a deep posterior part of the tympanosquamosal 

recess, as seen in Platanista; an involucrum of the tympanic bulla that is transversely narrow in ventral view, 

as seen, although not to as great an extent, in Platanista

and Zarhachis (see Muizon, 1987); a median furrow 

on the tympanic bulla that is long anteriorly; an endocranial opening of the facial canal that is lateral to 

the spiral cribriform tract, as in Huaridelphis, Phocageneus, and Platanista; and a malleus that has a welldefined hook for the manubrium, as in Pomatodelphis

and Zarhachis, and a tubercule that is longer than the 

articular facets for the incus (see Muizon, 1985, 1987). 

However, USNM V 24425 lacks any fossa for the pterygoid sinus in the medial part of the frontal groove, an 

articular process on the periotic, and a lateral furrow 

on the tympanic bulla, all features observed in platanistids and squalodelphinids (Muizon, 1987; Lambert et 

al., 2014; Boersma et al., 2017; Godfrey et al., 2017; 

Bianucci et al., 2020).

Considering the combination of characters discussed 

above, including autapomorphies and characters shared with 

two major odontocete clades, we cannot include the new taxon 

in any known family or superfamily. More information, for 

example, on the currently unknown morphology of the facial 

area of the skull, would be needed to narrow down its affinities. Taking into account the highly unusual features of the 

basicranium area, one may suggest that USNM PAL 244525 

represents an abnormal, pathological individual. Indeed, the 

strongly modified anatomy of the squamosal, more specifically, 
NUMBER 107 • 167

the shortened mandibular fossa, inevitably had implications 

on the mechanical abilities of the jaws, including the degree 

to which they could be abducted, considering the anteriorly 

prominent postglenoid process. Furthermore, marked changes 

at the level of the distribution of bone in the tympanic region 

(greatly thickened sigmoid process and accessory ossicle versus 

reduced involucrum) probably modified the hearing abilities 

of this odontocete (see Nummela et al., 1999; Cranford et al., 

2010). Several arguments speak in favor of a nonpathological 

individual: (1) all paired cranial elements (including ear bones 

and squamosals) are roughly symmetrical, with unusual features being observed on both sides, and (2) bone surfaces for 

unusual features are smooth and regular. We therefore suggest 

that an aberrant odontocete, most likely with unusual feeding 

and hearing abilities, once swam the eastern coast of the United 

States. Hopefully, more complete specimens will further improve our knowledge of this unique animal, maybe as specialized as the walrus-like dolphin Odobenocetops (e.g., Muizon 

and Domning, 2002).

Unnamed Odontoceti Incertae Sedis

In the following sections we briefly describe a series of cranial 

and mandibular specimens from the Miocene of Calvert Cliffs and 

area that we could not confidently refer to a known species, genus, 

family, or higher-rank odontocete clade and that we estimate to 

be too fragmentarily preserved to properly diagnose a new species. These remains suggest that the local rich Miocene odontocete 

diversity of the Atlantic Coastal Plain is not yet fully known.

Partial lower jaw from the Calvert Formation 

(Popes Creek Sand, Potomac River)

FIGURE 2.67

Here we describe another unique Chesapeake Group odontocete that is presently known from only a partial lower jaw 

from one individual.

Locality. The two pieces were recovered from the 

base of Popes Creek Sand, approximately 15 cm above the contact with the Eocene Nanjemoy Formation, all about 3 m above 

beach level, Charles County, Maryland.

Horizon and Age. Popes Creek Sand unit, 

Fairhaven Member, base of the Calvert Formation, Early Miocene (Burdigalian).

Known Range. Popes Creek Sand unit (early Burdigalian) of the Calvert Formation.

Referred Material. CMM-V-8988, two sections 

(Figure 2.67) of a bilaterally compressed odontocete partial lower 

jaw found, prepared, and donated to CMM by Gary Grimsley. 

Description. CMM-V-8988 (Figure 2.67) consists of 

two adjoining segments within the symphyseal region of a partial 

lower jaw. The combined length of the two adjacent segments is 

approximately 340 mm. Along its preserved length, the jaw gently curves dorsally. The two mandibular rami are not completely 

fused in the longer anterior section of the jaw, whereas the rami 

are fused throughout their length in the shorter posterior segment.

Anteriorly, the vertical depth of the jaw is approximately 

34 mm; posteriorly, it increases to a maximum midline depth 

of 47 mm. Despite this significant vertical depth, the jaw is only 

FIGURE 2.67. CMM-V-8988, odontocete partial lower jaw in (A) dorsal and (B) right lateral views.
168 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

27 mm wide (transversely) posteriorly, such that the depth-towidth ratio is only 0.57. Twenty-four open alveoli are preserved 

along the longer right side of the jaw. Oval alveoli are separated 

by bony septa (Figure 2.67). The anteroposteriorly oval alveoli 

are approximately 10 mm long. The jaw is widest at about twothirds the length of the ramus. In cross section, the outline of the 

fused mandibles approximates an inverted teardrop.

Remarks. No other Chesapeake Group odontocete possesses 

as deep and bilaterally compressed a lower jaw as in CMM-V-8988. 

In terms of its overall shape, CMM-V-8988 resembles the lower jaw 

of Goniodelphis hudsoni, the purported iniid from the Early Pliocene of Florida (Allen, 1941). If Goniodelphis is, indeed, Pliocene 

in age (and Allen expressed some doubt), there would be at least 

10 million years (perhaps 15) separating these two taxa. In terms 

of its bilateral compression, CMM-V-8988 resembles the anterior 

end of the mandible of the Pliocene phocoenid Semirostrum ceruttii, from the Pliocene San Diego (4.2–1.6 Ma) and Purisima (5–2.5 

Ma) Formations of California (Racicot et al., 2014). It differs from 

Semirostrum in that in the latter the anterior part of the mandible 

is nearly edentulous. Another North American odontocete with a 

comparable bilaterally compressed lower jaw is an unnamed form 

from the Early Miocene Nye Formation of coastal Oregon, United 

States (Barnes et al., 2010: fig. 10). The specimen (LACM 131112) 

consists of a partial lower jaw preserving an edentulous segment 

of the symphysis. Barnes et al. (2010) found that it most closely 

resembled a section of the bilaterally compressed mandible of the 

extant Ganges River dolphin Platanista gangetica, but from a larger 

individual by a factor of three. All three of these taxa have strongly 

transversely compressed ankylosed mandibles with alveolar grooves 

that are very close to each other. CMM-V-8988 is comparable in 

size to LACM 131112, but they differ in that CMM-V-8988 does 

not appear to possess a lateral groove like LACM 131112 (and 

Platanista). There are two platanistids known from the lowermost 

Calvert Formation, Araeodelphis and Grimadelphis; however, we 

do not think that this partial mandible derives from either of these, 

considering, for example, the different proportions of the cross section of the rostrum (transversely wider than high in both Araeodelphis and Grimadelphis).

In South America, Pontoplanodes argentinus of Ameghino 

(1891) was based on a fragment of a very narrow rostrum, with 

tooth rows closely approximated as in Goniodelphis, but with 

rather remarkable long and narrow alveoli.

Partial lower jaw from the Calvert Formation 

(south of Plum Point, Calvert Cliffs)

FIGURE 2.68

Here we describe another unique Chesapeake Group odontocete that is presently known from only a section of lower jaw from 

one individual. This partial mandible could belong to an alreadynamed odontocete, but that association has not yet been made.

Locality. The section of the lower jaw was recovered 

south of Plum Point, Calvert County, Maryland.

Horizon and Age. SZ 11 within the Plum Point 

Member of the Calvert Formation. This bed is early Middle Miocene (Langhian).

Known Range. SZ 11 (Langhian), Calvert Formation.

Referred Material. CMM-V-10002, a single section (Figure 2.68) of a partial odontocete lower jaw found, prepared, and donated to CMM by Gary Grimsley. 

Description. CMM-V-10002 (Figure 2.68) consists of 

a single segment of a left mandible. The length of the segment is 

approximately 384 mm, preserving part of the symphyseal region 

anteriorly, back to a portion of the coronoid area posteriorly. In 

medial view, approximately 60 mm of the unfused symphysis are 

preserved. However, it is not possible to say how much longer it 

would have been in life. In lateral view, the jaw curves gently dorsally along its preserved length. In the same view, the alveolar surface of the jaw is slightly concave. Six mental foramina parallel the 

tooth row, separated one from another by distances ranging from 

16 to 37 mm. The alveoli are directed dorsally in the posterior section of the mandible, but they gradually turn to face dorsolaterally 

as one moves toward the front of the ramus. The circular alveoli 

range in diameter from 9 mm posteriorly to 11 mm anteriorly. 

Posteriorly, adjacent alveoli are separated by only a very thin bony 

septum. Anteriorly, the bony septum can be 6 mm thick. So anteriorly, the alveoli are both larger and more widely spaced.

The maximum bilateral width and height of the mandible in 

the symphyseal region are 21 and 29 mm, respectively.

Eight teeth are preserved in CMM-V-10002. They all protrude from the jaw approximately 14 mm as measured from the 

medial side of the preserved ramus. The preserved height of the 

enamel-covered crown ranges from about 7 to 9 mm, ascending 

anteriorly. Every tooth exhibits strong apical wear, more so on 

posterior teeth, where most teeth are worn both mesially and 

distally, showing that upper and lower teeth occluded. The labial 

(i.e., cheek) surface of the crown enamel is smooth, whereas the 

lingual (i.e., tongue) side is wrinkled. There do not appear to 

have been any accessory cusplets on these teeth.

Remarks. Among the local delphinidans, this partial 

mandible is too large to have come from Brevirostrodelphis, 

Kentriodon pernix, Pithanodelphis, Pictodelphis, or Westmorelandelphis and too small to have come from Hadrodelphis, Macrokentriodon, Miminiacetus, Lophocetus, or Cammackacetus. In 

terms of tooth size and morphology, we can exclude it from having 

come from Brevirostrodelphis, Kentriodon pernix, Hadrodelphis, 

Macrokentriodon, Miminiacetus, Pictodelphis, Pithanodelphis, 

or Westmorelandelphis. Teeth are not yet known for Lophocetus

and Cammackacetus. However, both Lophocetus and Cammackacetus are stratigraphically distant (SZ 22–24) from SZ 11, from 

which this mystery mandible originated. On that basis alone, it 

seems thus unlikely that it pertains to either of those taxa. This 

mandible would appear to derive from an odontocete intermediate in size between the small forms comparable in size to K. pernix

and the larger forms in the size range of Hadrodelphis calvertense.
NUMBER 107 • 169

Rostrum from the St. Marys Formation

FIGURE 2.69

Locality. Chesapeake Ranch Estates, Lusby, Calvert 

County, Maryland, north of Driftwood Beach.

Horizon, Age, and Known Range. SZ 22–23 

of the Little Cove Point Member (Tortonian) of the St. Marys 

Formation.

Referred Material. USNM PAL 526574, a partial 

rostrum with several teeth in alveoli, found by Elizabeth M. 

Cridlin and donated to the Smithsonian Institution.

Description. USNM PAL 526574 (Figure 2.69) preserves an odontocete partial rostrum. The proximal break appears to be just anterior to the antorbital notch, whereas the distal 

break leaves an unknown length of the tip of the rostrum lost, although the descending dorsal margin of the rostrum does not give 

the impression that much of the anterior end of the snout is missing. The rostral segment is 195 mm long, with alveoli for 22 teeth 

on the left side and 20 teeth on the right. Alveoli are small, with 

transverse diameters ranging between 3.5 and 4 mm and interalveolar septa between 1.5 and 3 mm thick. Remains of 10 teeth 

are still in their respective alveoli. Anteriorly, the tooth rows are 

very nearly parallel and separated by only 8 mm (Figure 2.69C). 

FIGURE 2.68. CMM-V-10002, odontocete partial lower jaw in (A) left lateral view and (B) lingual view of teeth. Scale bar for B equals 10 mm.
170 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

At about the midpoint in the preserved length of the rostrum, the 

tooth rows diverge laterally and then posteriorly curve up slightly 

onto the lateral surface of the rostrum (Figure 2.69B,D). There 

is no dorsal opening of the mesorostral canal, as the premaxillae 

abut throughout their dorsomedial presentation (Figure 2.69A). 

The rostrum is compressed bilaterally, with a cross section being 

higher than wide for most of its length and a dorsal keel made 

of the joined premaxillae. The anterior end of the rostral segment curves slightly to the right. The posterior left dorsolateral 

face of the rostrum is concave, whereas the right one is globally 

convex, a most unusual condition for an odontocete rostrum. 

Furthermore, dorsally, the suture between the premaxillae curves 

to the right over the top of this concavity. The asymmetry of that 

median line follows the curve, although toward the posterior extremity of the fragment, it crosses the sagittal plane and ends left 

of center. The lateral maxilla-premaxilla suture is only faintly visible, the lateral surface of the rostrum being roughly continuous 

and transversely convex in the anterior half. Toward the posterior 

FIGURE 2.69. (A–D) USNM PAL 526574, odontocete partial rostrum in dorsal, right lateral, ventral, and left lateral 

views, respectively. Specimen whitened with sublimed ammonium chloride to improve contrast.
NUMBER 107 • 171

end of the specimen, both sides of the rostrum are covered in an 

anastomosing pattern of vascular sulci. A comparable network 

of anastomosing sulci has been observed on the surface of the 

pachyosteosclerotic rostrum of several extinct ziphiids, for example, Aporotus recurvirostris (see Lambert, 2005b). An anteroposteriorly elongated depression filled with sediment located on 

the left side at about two-thirds of the length of the specimen 

may correspond to a dorsal infraorbital foramen; it is followed 

posteroventrally by a sulcus.

Remarks. Although the rostral segment is asymmetrical, 

it does not appear to be in any way the result of a pathology. Furthermore, in holding this segment adjacent to the type of the pontoporiid Stenasodelphis russellae, they do not appear compatible 

(i.e., not from the same taxon). The rostrum of Stenasodelphis

is presently unknown, and the latter is the only odontocete from 

the St. Marys Formation comparable in size to which the rostral 

segment described here could belong. This partial rostrum appears to derive from yet another unknown odontocete from the 

Chesapeake Group.

Pathological rostra

FIGURE 2.70

Odontoceti Incertae Sedis

(Illustration by Tim Scheirer)

Known Range. Calvert and Choptank Formations 

(Serravallian).

Referred Material. CMM-V-2663, partial rostrum (Figure 2.70), SZ 13, Calvert Formation; USNM PAL 

412120, partial rostrum, Choptank Formation; USNM PAL 

412124, partial rostrum, Choptank Formation; USNM PAL 

425487, partial rostrum, Chesapeake Group; USNM PAL 

452910, partial rostrum, Calvert Formation; and USNM PAL 

534014, partial rostrum, Chesapeake Group. 

Description. Seven Miocene odontocete partial rostra (six specimens from the Chesapeake Group of Maryland, 

one from the Chesapeake Group of Virginia) exhibit periostitis, of unknown etiology, characterized by proliferative bone 

growth (Gerholdt and Godfrey, 2010). Periostitis is an inflammation of the periosteum secondary to a predisposing event 

such as a fracture or infection. Computed tomography (Figure 

2.70C) revealed that the lesions are limited to the premaxillae and that they became progressively swollen and gnarled, 

as evidenced by the onion-like layering within the deformity 

(Gerholdt and Godfrey, 2010).

Remarks. The level of maturity and degree of organization of the periostitis indicates that it likely developed over 

a period of months or years in these individuals (Gerholdt and 

Godfrey, 2010). Given this length of time, these pathologies 

seem not to have been life-threatening despite the size and shape 

of most of these periosteal reactions.

Nomina Dubia

In this section, we briefly comment on fragmentary odontocete remains from the Chesapeake Group that previously led 

to the description of new species and that are here deemed to be 

not sufficiently diagnostic to represent valid species. In the same 

paper in which Kellogg (1955) described Lophocetus pappus 

(now Miminiacetus pappus), he also described two lesser-known 

forms from Calvert Cliffs: Pelodelphis gracilis and Tretosphys 

gabbii. Although both taxa are now considered nomina dubia, 

the specimens are illustrated here because someone might eventually find, for each, a diagnosable skull with an associated lower 

jaw sufficient to establish their taxonomic validity.

Pelodelphis gracilis Kellogg, 1955

FIGURE 2.71

Holotype. USNM V 13471, ankylosed mandibles 

(Figure 2.71A) lacking distal ends of both rami; posterior portion of right mandible incomplete. 

Locality. Approximately 533 m north of the old pier 

at the end of Governor Run Road, Calvert County, Maryland 

(Kellogg, 1955).

Horizon and Age. In the sandy clay of SZ 14 

(about 46 cm above contact with SZ 13; Kellogg, 1955). Calvert 

Formation, Middle Miocene.

Referred Material. USNM V 10715, right and 

left mandibles (Figure 2.71B,C), essentially complete to posterior end of symphysis, sandy clay of SZ 5 above oyster shell 

layer, 1.2 m above beach level, South Chesapeake Beach, Calvert County, Maryland. Calvert formation, late Early Miocene.

Tretosphys gabbii (Cope, 1868)

FIGURE 2.72

During the year 1868, Prof. E. D. Cope received a miscellaneous collection of vertebrae and other skeletal 

fragments from a Maryland correspondent, James T. 

Thomas. Included among these bones was the caudal 

vertebra on which Cope based the name Delphinapterus gabbii. Cope did not designate a precise locality. From residents of Charles County information has 
172 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

since been obtained relative to the location of the residence of Thomas near the Patuxent River. Although it 

cannot now be stated with certainty, in all probability 

this type vertebra and the other specimens described 

by Cope were found by slaves who were digging shell 

marl on the De la Brooke estate. No specimens referable to this species were received by the United States 

National Museum until 1918, when Rodney B. Harvey 

excavated the specimen hereinafter described in the cliff 

south of Chesapeake Beach, Md. (Kellogg, 1955:143)

Holotype. ANSP 11234, an imperfectly preserved 

anterior caudal vertebra that lacks the neural spine and transverse processes. The USNM has a cast of the holotype, USNM 

V-10841.

Horizon and Locality. Probably excavated by 

slaves of James Thomas in marl bed on De la Brooke estate, 

about 1.6 km east of Patuxent, Charles County, Maryland. Calvert 

Formation, Miocene.

Referred Material. Following Kellogg (1955): 

USNM V 10709 (Figure 2.72), sections of mandibles, maxillae, 

FIGURE 2.70. CMM-V-2663. (A, B) Odontocete partial rostrum in dorsal and left lateral views, respectively. (C) Computed tomography (CT) scan transverse section images through B, as indicated by the thick lines. (D) Partial rostrum 

in ventral view showing alveoli. Specimen whitened with sublimed ammonium chloride. Modified from Gerholdt and 

Godfrey (2010).
NUMBER 107 • 173

FIGURE 2.71. Pelodelphis gracilis. Lower jaws and teeth. (A) USNM V 13471, holotype, mandible in dorsal view. 

(B) USNM V 10715, partial left mandible with two teeth in situ, in lateral view. (C) Teeth from USNM V 10715, 

from the original publication by Kellogg (1955), edited in Adobe Photoshop, originally whitened with sublimed ammonium chloride. Scale bar for C equals 10 mm.
174 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

and premaxillae; teeth; hyoid bones; one thoracic and one lumbar vertebra; an ulna; a partial radius; a carpal; a phalanx; and 

several rib fragments. Calvert Formation, Miocene. 

Remarks. Kellogg (1955) described the mandibles, 

rostrum, teeth, hyoid bones, vertebrae, and elements of the forelimb in detail.

On the basis of the distinctive morphology of the tooth 

crown pattern, Whitmore and Kaltenbach (2008) attributed four 

additional specimens to Tretosphys gabbii. These associated partial right and left dentaries (USNM PAL 425670) and three isolated teeth (USNM V 26216, USNM PAL 360447) derive from 

the Pungo River Formation (an Early Miocene Calvert Formation equivalent) from the Aurora Phosphate Mine in Aurora, 

North Carolina.

Unfortunately, only a very small portion of the right maxilla of USNM V 10709 is known (Kellogg, 1955: plate 17-3), 

and the referral of this specimen to the same species as the holotype caudal vertebra USNM V 11234 is not well supported. Because of the low diagnostic value of both specimens, we consider 

Tretosphys gabbi to be a nomen dubium and identify the referred 

specimens as Odontoceti indet.

DISCUSSION

Faunal Comparison for Calvert Cliffs’ Odontocetes

Table 2.10 is not an exhaustive list of odontocete taxa recorded along Calvert Cliffs, but rather a list of taxa for which 

closely related forms (same species, same genus, or same subfamily) are known from other localities, with most of these records 

being based on cranial material. At the species level, the best 

match is with the Antwerp area (Belgium), sharing one physeterid (Orycterocetus crocodilinus), three eurhinodelphinids 

(Xiphiacetus bossi, X. cristatus, and Schizodelphis morckhoviensis), and at least one early delphinidan (Pithanodelphis cornutus

and, possibly, Kentriodon pernix). Six genera are shared with the 

Mediterranean, and five are shared with the Aurora Phosphate 

Mine, North Carolina. 

The odontocete fauna described herein displays a significant degree of endemism. Of the 29 named species, 18 of 

them (Squalodon murdochi, “Aulophyseter” mediatlanticus,

Araeodelphis natator, Grimadelphis spectorum, Zarhachis 

flagellator, Pomatodelphis santamaria, S. barnesi, Brevirostrodelphis dividum, Hadrodelphis calvertense, Macrokentriodon 

morani, Lophocetus calvertensis, Herbeinodelphis nancei, 

Cammackacetus hazenorum, Pictodelphis kidwellae, Westmorelandelphis tacheroni, Stenasodelphis russellae, Caolodelphis

milleri, and Enigmatocetus posidoni), or 62%, are for now 

known only from the Calvert Cliffs region and could thus be 

tentatively characterized as endemic to the immediate area. If 

the census is extended to include the Atlantic Coastal Plain 

(i.e., the western North Atlantic region, encompassing Aurora 

Phosphate Mine in North Carolina and localities in Florida), 

the number rises to 24 (adding Squalodon calvertensis, 

S. whitmorei, Orycterocetus crocodilinus, Phocageneus venustus, Pomatodelphis inaequalis, and Miminiacetus pappus), or 

83%. Finally, if the entire North Atlantic is included (adding 

Xiphiacetus bossi, X. cristatus, Schizodelphis morckhoviensis,

Kentriodon pernix, and Pithanodelphis cornutus), the number 

rises to 29, thus 100%. All of these percentages are probably 

artificially high because the actual geographic range of each 

species was probably larger than suggested by the limited geographic range (from one, two, or three locations) from which 

the species are presently known. The home ranges of extant 

odontocetes vary widely, from a few that have a very limited 

geographic range, like the Amazon river dolphin Inia geoffrensis, limited to two freshwater river basins in South America 

(the Amazon and the Orinoco Rivers), to many more like the 

cosmopolitan sperm whale Physeter macrocephalus, known 

from all oceanic regions of the world (except the High Arctic; 

Carwardine et al., 2002).

The odontocete fossil record from the Calvert Cliffs is by 

far the richest for the whole North Atlantic because of the vertical (temporal) and lateral extent of the available outcrops, as 

well as their continuous renewal and the collection effort by 

both professional and avocational paleontologists. Therefore, 

it would not be surprising if species only rarely encountered 

along the local sections indeed occupied other regions of the 

North Atlantic realm but have not yet been discovered there 

because the outcrops are more limited in area, the available 

deposits do not match the paleoenvironments inhabited by 

these species, the species have been identified only at a higher 

rank (e.g., Pomatodelphininae indet. and Squalodon sp. in Antwerp), or the species have been erroneously identified. Some 

early delphinidans known from a limited number of fragmentary remains may, for example, be erroneously referred to a 

well-known species, like Kentriodon pernix. As demonstrated 

by this work, it is now known that multiple small delphinidan 

species occurred in the North Atlantic during the Miocene. The 

reassessment of other Miocene localities in light of the present 

review will undoubtedly provide new matches between faunal 

lists and, hopefully, clarifications of taxonomic affinities for 

more fragmentary specimens.

Some species known from a very limited number of specimens along Calvert Cliffs (e.g., some physeteroids and all 

ziphiids) may have inhabited more pelagic regions, whereas 

more common taxa (e.g., the hyper-longirostrine eurhinodelphinids) are proposed to have been residents of the coastal 

region. Nevertheless, it is interesting to note that the latter 

family ranks as the first for the number of species shared between Calvert Cliffs and the southern margin of the North Sea 

Basin (Antwerp), providing examples of presumably coastal 

species displaying a relatively broad distribution across a large 

oceanic basin.

It is noteworthy that none of the Miocene odontocete species known from Maryland and Virginia are yet known from 

the South Atlantic or from any other ocean. Future work in 
NUMBER 107 • 175

FIGURE 2.72. Tretosphys gabbii. USNM V 10709. (A) Incomplete lower jaw preserving a portion of the fused symphyseal region. (B–D) Teeth from the original publication (Kellogg, 1955) edited in Adobe Photoshop (scale bar = 10 mm). 

(E) Left ulna in medial view.
176 

• SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY TABLE 2.10. Miocene odontocetes from along Calvert Cliffs and areas for which closely related forms (same species, same genus, or same subfamily) are known from other localities. A dash (—) indicates no related forms have been found in a particular region. Aurora Calvert Cliffs, Phosphate Mine, Odontocete Clade Maryland, USA North Carolina, USA Florida, USA Antwerp, Belg.lium Mediterranean California, USA Squalodontidae Squalodon Squalodon — Squalodon Squalodon — calvertensis, calvertensis, antwerpiensis, bariensis, S. whitmorei, S. whitmorei Squalodon sp. S. bellunensis, S. murdochi S. catulli, S. peregrinus , Squalodelphinidae Phocageneus Phocageneus cf. — — — — venustus P. venustus Platanistidae Zarhachis Pomatodelphis sp. Pomatodelphis Pomatodelphininae Zarhachis sp., — flagellator, inaequalis, indet. Pomatodelphis Pomatodelphis P. bobengi sp. inaequalis, Pomatodelphis 

 santamaria

Physeteroidea Orycterocetus Physeteridae cf. — Orycterocetus Orycterocetus sp. —

 crocodilinus Orycterocetus crocodilinus

Eurhinodelphinidae Xiphiacetus bossi, Xiphiacetus sp. — Xiphiacetus bossi, Xiphiacetus aff. —

X. cristatus, X. cristatus, X. bossi,Schizodelphis Schizodelphis Schizodelphis morckhoviensis, morckhoviensis sulcatusS. barnesi

Delphinida Kentriodon pernix, Kentriodon — Kentriodon aff. — Kentriodon

Pithanodelphis schneideri aff. K. pernix, obscurus,  cornutus, Atocetus, Pithanodelphis Liolithax kernensis,Miminiacetus Lophocetinae aff. cornutus Lophocetus pappus, Miminiacetus repenningiLophocetus pappus calvertensis
NUMBER 107 • 177

promising, cetacean-rich Early and Middle Miocene deposits of 

the Pisco Basin (Peru) may still reveal closer connections between 

the northwestern Atlantic and southeastern Pacific during the 

Early Neogene (see Bianucci et al., 2020; Bosio et al., 2020a).

Stratigraphic Distribution

In terms of their stratigraphic distribution, collectively, the 

odontocetes from the Miocene of Maryland and Virginia range 

in age from the Aquitanian through to the Tortonian (Figures 

2.73, 2.74), with the large majority occurring within the Burdigalian, Langhian, and early Serravallian (the latter two being the 

most species rich). The Langhian and Serravallian encompass the 

Miocene Climatic Optimum (ca. 17–15 Ma), a time when global 

average temperatures may have been 4°C to 5°C above today’s 

average temperatures, at least for parts of this interval (Tripati et 

al., 2009; Methner et al., 2020).

Nineteen of the 37 taxa listed in Figures 2.73 and 2.74 are 

known only from single SZs. Others, like Zarhachis flagellator, 

Squalodon calvertensis, and Kentriodon pernix, are known to 

span multiple SZs, 14, 13, and 13, respectively. Taxa known 

from single zones are probably a reflection of the limitations of 

preservation in the fossil record.

ACKNOWLEDGMENTS

This work would not have been possible were it not for the 

many amateur and professional paleontologists who have collected odontocete fossils for more than 150 years from along 

Calvert Cliffs and elsewhere in Maryland and Virginia. Specimens 

referenced in this work were collected by Aaron A. Alford, Chris 

Allison, Elizabeth R. Ashby, Wallace L. Ashby, Gretchen Baugh, 

Anna Kay Behrensmeyer, Alfred Berling, M. Starr Best, Alexander Bohaska, David J. Bohaska, George N. Bohaska, Paula W. 

Bohaska, Norman H. Boss, James M. Bovis, P. Buckley, Frank 

Burns, Martin Burton, David S. Cammack, Richard Carr, 

Gerald Case, Dawn Cifani, Robert M. Coffin, R. Lee Collins, 

Noah Cook, William “Bill” Counterman, Elizabeth M. Cridlin, 

Aurelia De Gasparis, J. De Gasparis, T. Dudley, Jim Earman, 

Mike Ellwood, Douglass R. Emlong, Ralph E. Eshelman, 

Hellen “Pat” Fink, George C. Fonger, William F. Foshag, 

Roland A. Fowler, Mary Theresa (Fox) Gascon, Chris Gateau, 

David Gates, Charles L. Gazin, Raymond M. Gilmore, Cliff Ginn, 

Stephen J. Godfrey, William “Pat” Gotsis, D. Goudagni, Frederick 

Von Hoff Grady, Fredda Granados, Gary Grimsley, Kyle Grimsley, Stephen Groff, John Gurche, Robert M. Hazen, I. M. Hellmer, 

D. Heminway, Mark Herbst, Hammond Hobbs, Jean Hooper, 

Howard Hruschka, Ronald Ison, Andrew T. Jackson, Howard 

Jackson, George J. Jacobs, Jeremy F. Jacobs, David Johnson, 

Marcus Jones, William D. Jones, James A. Kaltenbach, Remington Kellogg, Mary Kidd, Charles L. Kimbell, J. F. Lawson, 

W. Gardiner Lynn, D. B. Mackie, Donald Malick, Francis Markoe Jr., Peter McCreary, R. Mongelli, Donald J. Morgan III, Paul 

R. Murdoch Jr., Arlton C. Murray, Albert C. Myrick Jr., John 

R. Nance, Eric Nelson, Bruce Newell, Arnold W. Norden, Chip 

Ohlhaver, John Ott, William Palmer, F. Pearce, M. Pechacek, 

Victor J. Perez, Jack Peterson, William “Bill” F. Prochownik III, 

David Rhea, Norman L. Riker, Betty “Sandy” Roberts, R. Rogers, 

Anna Ruhaka, Kurt M. Savoie, John Seyfried, John Shea, Mark 

M. Shoemaker, Derek Siddons, Connie Smith, J. Homer Smith, 

Theresa “Tee” Smith, Chuck Soares, Gladwyn B. Sullivan, Eric 

Supensky, Taylor Swanson, Sigmund Sweda, Ben Tacheron, Scott 

Tarlo, Calvin E. Taylor, James T. Thomas, Sam Thompson, Frederick W. True, Yasemin Tulu, Joseph Turner, Martha C. Weber, 

Scott Werts, James W. Westgate, Alexander Wetmore, Michael 

White, and Frank C. Whitmore Jr. We also make special reference 

to the sadly now-unknown slaves who, in the nineteenth century, 

probably excavated a type vertebra and the other specimens described by Cope while digging shell marl near the Patuxent River 

in Maryland.

Additionally, community associations and private property 

owners have been extraordinarily generous in allowing us to 

quarry Miocene odontocetes for safekeeping at either the Calvert 

Marine Museum or the National Museum of Natural History, 

Smithsonian Institution. They include the Chesapeake Ranch Estates, Calvert Beach Civic Association, Long Beach Civic Association, Matoaka Beach Cabins, Western Shores Civic Association, 

Robert and Margee Hazen, Kenwood Beach Civic Association, 

Scientists Cliffs Association, Warriors’ Rest Sanctuary (Maryland 

Department of Natural Resources), Wilson Freeland, Chesapeake 

Heights on the Bay, Alexandra M. Llewellyn and the Clancy Estate, Ken and Martha Mathews, Charles “Chip” N. Andreae, Patricia “Pat” Fischer, Fairview Estates, the Lambourne family of 

Angelica Farm, Ray Bacorn, Emily Woo, the Garchen Tara Monastery, Tom Heath, Roosevelt Cliffs, Peter Wharton and Gray 

Hautaluoma, Thomas V. “Mike” Miller Jr. (deceased), Camp 

Roosevelt Homeowners Association, Holiday Beach, Over Water 

LLC, Chesapeake Beach, Virginia Quigley (deceased), Thomas 

Briscoe, and the Board of Charles County Commissioners.

Brenna Litynski and Tim Scheirer expertly created the life 

renderings of the odontocetes illustrated herein. We also express 

our sincerest thanks to John R. Nance for his help with access 

to the fossil odontocetes housed in the Calvert Marine Museum. 

Furthermore, we gratefully acknowledge David J. Bohaska, 

James G. Mead, John Ososky, Charley Potter, and Nicholas D. 

Pyenson for providing access to the collections of modern and 

fossil dolphins in the National Museum of Natural History. We 

also thank Giovanni Bianucci and Christian de Muizon for providing us many photos of odontocete fossil specimens, mostly 

from Europe and South America, used in our comparisons 

and, on behalf of author O.L., the many discussions on extinct 

odontocetes over the past 20 years. Figure 2.1 was created with 

help from Robert E. Weems.
178 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

FIGURE 2.73. Stratigraphic distribution of the named odontocetes (at least at the genus level) known from the Chesapeake Group 

of Maryland and Virginia. The surprisingly long stratigraphic range of some species could, in some cases, be due to (1) the inclusion 

of specimens that may prove diagnostic at only the genus (or even a higher rank) level or (2) the fact that some species’ diagnoses are 

not yet fully satisfactory (see for example the comments in the Eurhinodelphinidae section above). Such long ranges should thus be 

considered with caution, pending further detailed comparisons of more fragmentary specimens and the revision of some diagnoses. 

The Popes Creek Sand (PCS) is not a Shattuck-Zone but is included here as a distinct unnumbered bed within the Shattuck scheme. 

Abbreviations: B.C. = Boston Cliffs; Con. = Conoy; Drum. = Drumcliff; G.R. = Governor Run; L. Cove Pt. = Little Cove Point; 

St.L. = St. Leonard; W.Pt. = Windmill Point.
NUMBER 107

• 179

FIGURE 2.74. Stratigraphic distribution of the unnamed odontocetes known from the Chesapeake Group of Maryland and Virginia. Note that the Popes Creek Sand (PCS) is not a Shattuck-Zone, but it is included here as a distinct unnumbered bed within the Shattuck scheme. Abbreviations: B.C. = Boston Cliffs; Con. = Conoy; Drum. = Drumcliff; G.R. = Governor Run; L. Cove Pt. = Little Cove Point; St.L. = St. Leonard; W.Pt. = Windmill Point.
180 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Many helpful comments from Mark D. Uhen, an anonymous reviewer, and Smithsonian Press Editorial Board member 

Nicholas D. Pyenson greatly improved earlier versions of this 

work, and we thank them. Dave Bohaska also provided reviews 

of several generations of this work and has our thanks. Gary 

Grimsley is also gratefully acknowledged for his very detailed 

and helpful reviews. It has been only a pleasure to work with 

Smithsonian Institution Scholarly Press director Ginger Minkiewicz and program assistant Myka Bangert to bring this effort to 

fruition.

The late John Pojeta (U.S. Geological Survey and Smithsonian Institution) welcomed S.J.G. into his lab so he could whiten 

some of the specimens illustrated herein with sublimed ammonium chloride.

This publication was made possible with funding from the 

citizens of Calvert County, Maryland, through the County Board 

of Calvert County Commissioners, and the Clarissa and Lincoln 

Dryden Endowment for Paleontology at the Calvert Marine Museum. Funding for Smithsonian Institution Scholarly Press comes 

from the citizens of the United States.

REFERENCES

Abel, O. 1901. Les Dauphins Vertebrates du Boldérien (Miocène supérieur) des 

Environs d’Anvers. I. Mémoires du Musée Royal d’Histoire Naturelle de Belgique, 1:1–95. https://doi.org/10.5962/bhl.title.16053

Abel, O. 1902. Les Dauphins Vertebrates du Boldérien (Miocène supérieur) des 

Environs d’Anvers. II. Mémoires du Musée Royal d’Histoire Naturelle de 

Belgique, 2:99–190. https://doi.org/10.5962/bhl.title.16053

Abel, O. 1905. Les Odontocètes du Boldérien (Miocène supérieur) des Environs 

d’Anvers. Mémoires du Musée Royal d’Histoire Naturelle de Belgique, 3:1–

155. https://doi.org/10.5962/bhl.title.15923Aguirre-Fernández, G., L. G. 

Barnes, F. J. Aranda-Manteca, and J. R. Fernández-Rivera. 2009. Protoglobicephala mexicana, a New Genus and Species of Pliocene Fossil Dolphin (Cetacea; Odontoceti; Delphinidae) from the Gulf of California, Mexico. Boletin 

de la Sociodad Geologica Mexicana, 61:245–265. https://doi.org/10.18268/

BSGM2009v61n2a13

Alfsen, A., M. Bosselaers, and O. Lambert. 2021. New Sperm Whale Remains from 

the Late Miocene of the North Sea and a Revised Family Attribution for the 

Small Crown Physeteroid Thalassocetus Abel, 1905. Comptes Rendus Palevol, 20:807–822. https://doi.org/10.5852/cr-palevol2021v20a39

Allen, G. M. 1921. Fossil Cetaceans from the Florida Phosphate Beds. Journal of 

Mammalogy, 2(3):144–159. https://doi.org/10.2307/1373603

Allen, G. M. 1941. A Fossil River Dolphin from Florida. Bulletin of the Museum of 

Comparative Zoology, 89:1–8.

Andrews, G. W. 1986. Miocene Diatoms from Richmond, Virginia. Journal of Paleontology, 60:497–538. https://doi.org/10.1017/S0022336000022010

Ameghino, F. 1891. Mamiferos y aves Fosiles Argentinas. Especies nuevas, adiciones y correcciones. Revista Argentina Historia Natural, 1(4):240–259.

Barnes, L. G. 1978. A Review of Lophocetus and Liolithax and Their Relationships 

to the Delphinoid Family Kentriodontidae (Cetacea: Odontoceti). Natural 

History Museum of Los Angeles County, Science Bulletin, 28:1–35.

Barnes, L. G. 1984. Fossil Odontocetes (Mammalia: Cetacea) from the Almejas 

Formation, Isla Cedros, Mexico. PaleoBios, 42:1–46.

Barnes, L. G. 1985a. The Late Miocene Dolphin Pithanodelphis Abel, 1905 

(Cetacea: Kentriodontidae) from California. Contributions in Science, 

Natural History Museum of Los Angeles County, 367:1–27. https://doi.

org/10.5962/p.208183

Barnes, L. G. 1985b. Fossil Pontoporiid Dolphins (Mammalia: Cetacea) from the 

Pacific Coast of North America. Contributions in Science, Natural History 

Museum of Los Angeles County, 363:1–34. https://doi.org/10.5962/p.208181

Barnes, L. G. 1992. The Fossil Marine Vertebrate Fauna of the Latest Miocene 

Almejas Formation, Isla Cedros, Baja California, México. In Primera Reunión Internacional sobre Geología de la Península de Baja California, ed. A. 

Carrillo-Chávez and A. Alvarez-Arellano, pp. 147–166. Memorias. La Paz, 

Mexico: Universidad Autónoma de Baja California Sur.

Barnes, L. G. 1998. The Sequence of Fossil Marine Mammal Assemblages in 

México. In Avances en Investigación. Paleontología de Vertebrados, ed. O. 

Carranza-Castañeda and D. A. Córdoba-Méndez, pp. 26–79. Publicación 

Especial 1. Pachuca, Mexico: Instituto de Investigaciones en Ciencias de la 

Tierra, Universidad Autónoma del Estado de Hidalgo.

Barnes, L. G. 2002. Evolutionary History of the Fossil Marine Mammals of México. 

In Avances en los Estudios Paleomastozoologicos, ed. M. Montellano-Ballesteros and J. Arroyo-Cabrales, pp. 125–225. Coleccion Cientifica, Serie Arqueologia. Mexico City: Instituto Nacional de Antropologia e Historia.

Barnes, L. G. 2006. A Phylogenetic Analysis of the Superfamily Platanistoidea 

(Mammalia, Cetacea, Odontoceti). Beitrage zur Palaontologie, 30:25–42.

Barnes, L. G. 2008. Miocene and Pliocene Albireonidae (Cetacea, Odontoceti), 

Rare and Unusual Fossil Dolphins from the Eastern North Pacific Ocean. 

Natural History Museum of Los Angeles County, Science Series, 41:99–152.

Barnes, L. G., T. Kimura, and S. J. Godfrey. 2010. The Evolutionary History and 

Phylogenetic Relationships of the Superfamily Platanistoidea. In Biology, 

Evolution, and Conservation of River Dolphins within South America and 

Asia, ed. M. Ruiz and J. M. Shostell, pp. 445–488. New York: Nova Science 

Publishers.

Barnes, L. G., and E. D. Mitchell. 1984. Kentriodon obscurus (Kellogg, 1931), a 

Fossil Dolphin (Mammalia: Kentriodontidae) from the Miocene Sharktooth 

Hill Bonebed in California. Contributions in Science, Natural History Museum of Los Angeles County, 353:1–23. https://doi.org/10.5962/p.226838

Barrick, R. E., A. G. Fischer, Y. Kolodny, B. Luz, and D. Bohaska. 1992. Cetacean 

Bone Isotopes as Proxies for Miocene Ocean Composition and Glaciation. 

Palaios, 7:521–531. https://doi.org/10.2307/3514849

Benites-Palomino, A., G. Aguirre-Fernández, J. W. Moreno-Bernal, A. Vanegas, and 

C. Jaramillo. 2020a. Miocene Freshwater Dolphins from La Venta, Huila, 

Colombia Suggest Independent Invasions of Riverine Environments in Tropical South America. Journal of Vertebrate Paleontology, 40:e1812078. https://

doi.org/10.1080/02724634.2020.1812078

Benites-Palomino, A., J. Vélez-Juarbe, R. Salas-Gismondi, and M. Urbina. 2020b. 

Scaphokogia totajpe, sp. nov., a New Bulky-Faced Pygmy Sperm Whale (Kogiidae) from the Late Miocene of Peru. Journal of Vertebrate Paleontology, 

39:e1728538. https://doi.org/10.7934/P3939

Benoit, J., S. Adnet, J.-L. Welcomme, and P.-H. Fabre. 2011. New Skull of Schizodelphis sulcatus Gervais, 1861 (Mammalia, Odontoceti, Eurhinodelphinidae) 

from the Lower Miocene of Pignan (Hérault, France) and Its Implications 

for Systematics of Eurhinodelphinidae. Geobios, 44:323–334. https://doi.

org/10.1016/j.geobios.2010.10.006

Bianucci, G. 1997. The Odontoceti (Mammalia: Cetacea) from Italian Pliocene. 

The Ziphiidae. Palaeontographia Italica, 84:163–192.

Bianucci, G. 2001. A New Genus of Kentriodontid (Cetacea: Odontoceti) from 

the Miocene of South Italy. Journal of Vertebrate Paleontology, 21:573–577. 

https://doi.org/10.1671/0272-4634(2001)021[0573:ANGOKC]2.0.CO;2

Bianucci, G. 2013. Septidelphis morii, n. gen. et sp., from the Pliocene of Italy: New 

Evidence of the Explosive Radiation of True Dolphins (Odontoceti, Delphinidae). Journal of Vertebrate Paleontology, 33:722–740. https://doi.org/10.108

0/02724634.2013.744757

Bianucci, G., G. Bosio, E. Malinverno, C. de Muizon, I. M. Villa, M. Urbina, and 

O. Lambert. 2018. A New Large-Sized Squalodelphinid (Cetacea, Odontoceti) from Peru Sheds Light on the Early Miocene Platanistoid Disparity and 

Ecology. Royal Society Open Science, 5:172302. https://doi.org/10.1098/

rsos.172302

Bianucci, G., A. Collareta, K. Post, A. Varola, and O. Lambert. 2016a. A New 

Record of Messapicetus from the Pietra Leccese (Late Miocene, Southern Italy): Antitropical Distribution in a Fossil Beaked Whale (Cetacea, Ziphiidae). 

Rivista Italiana di Paleontologia e Stratigrafia, 122:63–74.

Bianucci, G., C. Di Celma, W. Landini, K. Post, C. Tinelli, C. de Muizon, K. Gariboldi, E. Malinverno, G. Cantalamessa, A. Gioncada, A. Collareta, R. SalasGismondi, R. Varas-Malca, M. Urbina, and O. Lambert. 2016b. Distribution 

of Fossil Marine Vertebrates in Cerro Colorado, the Type Locality of the 

Giant Raptorial Sperm Whale Livyatan melvillei (Miocene, Pisco Formation, 

Peru). Journal of Maps, 12:543–557. https://doi.org/10.1080/17445647.20

15.1048315
NUMBER 107 • 181

Bianucci, G., C. Di Celma, M. Urbina, and O. Lambert. 2016c. New Beaked 

Whales from the Late Miocene of Peru and Evidence for Convergent Evolution in Stem and Crown Ziphiidae (Cetacea, Odontoceti). PeerJ, 4:e2479. 

https://doi.org/10.7717/peerj.2479

Bianucci, G., O. Lambert, and K. Post. 2007. A High Diversity in Fossil Beaked 

Whales (Odontoceti, Ziphiidae) Recovered by Trawling from the Sea Floor 

off South Africa. Geodiversitas, 29:561–618.

Bianucci, G., O. Lambert, and K. Post. 2010. High Concentration of Long-Snouted 

Beaked Whales (Genus Messapicetus) from the Miocene of Peru. Palaeontology, 53:1077–1098. https://doi.org/10.1111/j.1475-4983.2010.00995.x

Bianucci, G., O. Lambert, R. Salas-Gismondi, J. Tejada, F. Pujos, M. Urbina, 

and P.-O. Antoine. 2013. A Miocene Relative of the Ganges River Dolphin 

(Odontoceti, Platanistidae) from the Amazonian Basin. Journal of Vertebrate 

Paleontology, 33:741–745. https://doi.org/10.1080/02724634.2013.734888

Bianucci, G., W. Landini, and A. Varola. 1994. Relationships of Messapicetus longirostris (Cetacea, Ziphiidae) from the Miocene of South Italy. Bollettino 

della Società Paleontologica Italiana, 33:231–241.

Bianucci, G., and W. Landini. 2002. Change in Diversity, Ecological Significance and Biogeographical Relationships of the Mediterranean Miocene 

Toothed Whale Fauna. Geobios, 35 (Mémoire spécial 24):19–28. https://doi.

org/10.1016/S0016-6995(02)00045-1

Bianucci, G., and W. Landini. 2006. Killer Sperm Whale: A New Basal Physeteroid 

(Mammalia, Cetacea) from the Late Miocene of Italy. Zoological Journal 

of the Linnean Society, 148:103–131. https://doi.org/10.1111/j.1096-

3642.2006.00228.x

Bianucci, G., W. Landini, G. Valleri, L. Ragaini, and A. Varola. 2005. First Cetacean Fossil Records from Ecuador, Collected from the Miocene of Esmeraldas Province. Rivista Italiana di Paleontologia e Stratigrafia, 111:345–350.

Bianucci, G., W. Landini, and A. Varola. 1992. Messapicetus longirostris, a New 

Genus and Species of Ziphiidae (Cetacea) from the Late Miocene of “Pietra leccese” (Apulia, Italy). Bolletino della Società Paleontologica Italiana, 

31:261–264.

Bianucci, G., C. de Muizon, M. Urbina, and O. Lambert. 2020. Extensive Diversity 

and Disparity of the Early Miocene Platanistoids (Cetacea, Odontoceti) in 

the Southeastern Pacific (Chilcatay Formation, Peru). Life, 10:27. https://doi.

org/10.3390/life10030027

Boersma, A. T., M. R. McCurry, and N. D. Pyenson. 2017. A New Fossil Dolphin 

Dilophodelphis fordycei Provides Insight into the Evolution of Supraorbital 

Crests in Platanistoidea (Mammalia, Cetacea). Royal Society Open Science, 

4:170022. https://doi.org/10.1098/rsos.170022

Boersma, A. T., and N. D. Pyenson. 2015. Albicetus oxymycterus, a New Generic 

Name and Redescription of a Basal Physeteroid (Mammalia, Cetacea) from 

the Miocene of California, and the Evolution of Body Size in Sperm Whales. 

PloS ONE, 10:e0135551. https://doi.org/10.1371/journal.pone.0135551

Boessenecker, R. W., M. Churchill, E. A. Buchholtz, B. L. Beatty, and J. H. Geisler. 

2020. Convergent Evolution of Swimming Adaptations in Modern Whales 

Revealed by a Large Macrophagous Dolphin from the Oligocene of South 

Carolina. Current Biology, 30:3267–3273. https://doi.org/10.1016/j.

cub.2020.06.012

Bohaska, D. J. 1998. Fossil Marine Mammals of the Lower Miocene Pollack Farm 

Site, Delaware. In Geology and Paleontology of the Lower Miocene Pollack 

Farm Fossil Site, Delaware, ed. R. N. Benson. Delaware Geological Survey 

Special Publication, 21:179–191.

Boschma, H. 1938. On the Teeth and Some Other Particulars of the Sperm Whale 

(Physeter macrocephalus L.). Temminckia, 3:151–278.

Bosio, G., E. Malinverno, A. Collareta, C. Di Celma, A. Gioncada, M. Parente, 

F. Berra, F. G. Marx, A. Vertino, and M. Urbina. 2020a. Strontium Isotope 

Stratigraphy and the Thermophilic Fossil Fauna from the Middle Miocene 

of the East Pisco Basin (Peru). Journal of South American Earth Sciences, 

97:102399. https://doi.org/10.1016/j.jsames.2019.102399

Bosio, G., E. Malinverno, I. M. Villa, C. Di Celma, K. Gariboldi, A. Gioncada, 

V. Barberini, M. Urbina, and G. Bianucci. 2020b. Tephrochronology and 

Chronostratigraphy of the Miocene Chilcatay and Pisco Formations (East 

Pisco Basin, Peru). Newsletters on Stratigraphy, 53:213–247. https://doi.

org/10.1127/nos/2019/0525

Brandt, J. F. 1873. Untersuchungen über die Fossilen und Subfossilen Cetaceen Europa’s. Mémoires de L’Académie Impériale des Sciences de Saint-Petersbourg, 

ser. 7, 20(1):1–372.

Braulik, G. T., F. I. Archer, U. Khan, M. Imran, R. K. Sinha, T. A. Jefferson, C. 

Donovan, and J. A. Graves. 2021. Taxonomic Revision of the South Asian 

River Dolphins (Platanista): Indus and Ganges River Dolphins Are Separate 

Species. Marine Mammal Science, 37:1022–1059. https://doi.org/10.1111/

mms.12801

Brisson, M. J. 1762. Le Regnum Animale in Classes IX Distributum, Sive Synopsis 

Methodica Sistens Generalem Animalium distributionem in Classes IX, & 

Duarum Primarum Classium, Quadrupedum Scilicet & Cetaceorum, Particularem Dibvisionem in Ordines, Sectiones, Genera & Species. Paris: T. 

Haak. https://doi.org/10.5962/bhl.title.40361

Buchholtz, E. A. 2001. Vertebral Osteology and Swimming Style in Living and 

Fossil Whales (Order: Cetacea). Journal of the Zoological Society of London,

253:175–190. https://doi.org/10.1017/S0952836901000164

Buono, M. R., and M. A. Cozzuol. 2013. A New Beaked Whale (Cetacea, Odontoceti) from the Late Miocene of Patagonia, Argentina. Journal of Vertebrate 

Paleontology, 33:986–997. https://doi.org/10.1080/02724634.2013.752377

Cabrera, A. 1926. Cetaceos Fosiles del Museo de La Plata. Revista del Museo de 

La Plata, 29:363–411.

Carwardine, M., E. Hoyt, R. E. Fordyce, and P. Gill. 2002. The Nature Companions: Sharks and Whales. San Francisco, Calif.: Fog City Press.

Case, E. C. 1904. Systematic Paleontology: Mammalia. In The Miocene, ed. W. B. 

Clark, G. B. Shattuck, and W. H. Dall, pp. 3–58. Baltimore: Johns Hopkins 

Press.

Churchill, M., J. H. Geisler, B. L. Beatty, and A. Goswami. 2018. Evolution of Cranial Telescoping in Echolocating Whales (Cetacea: Odontoceti). Evolution, 

72:1092–1108. https://doi.org/10.1111/evo.13480

Churchill, M., M. Martínez-Cáceres, C. de Muizon, J. Mniechowski, and J. H. 

Geisler. 2016. The Origin of High-Frequency Hearing in Whales. Current 

Biology, 26:2144–2149. https://doi.org/10.1016/j.cub.2016.06.004

Collareta, A., F. C. Fulgosi, and G. Bianucci. 2019. A New Kogiid Sperm Whale 

from Northern Italy Supports Psychrospheric Conditions in the Early Pliocene Mediterranean Sea. Acta Palaeontologica Polonica, 64:609–626. 

https://doi.org/10.4202/app.00578.2018

Colpaert, W., M. Bosselaers, and O. Lambert. 2015. Out of the Pacific: A Second 

Fossil Porpoise from the Pliocene of the North Sea Basin. Acta Palaeontologica Polonica, 60:1–10. https://doi.org/10.4202/app.00115.2014

Cooper, C. L. 1935. Ammonium Chloride Sublimate Apparatus. Journal of Paleontology, 9:357–359.

Cope, E. D. 1866. Third Contribution to the History of the Balaenidae and Delphinidae. Proceedings of the Academy of Natural Sciences of Philadelphia, 

18:293–294.

Cope, E. D. 1867. An Addition to the Vertebrate Fauna of the Miocene Period, with 

a Synopsis of the Extinct Cetacea of the United States. Proceedings of the 

Academy of Natural Sciences of Philadelphia, 19:138–156.

Cope, E. D. 1868. Second Contribution to the History of the Vertebrata of the 

Miocene Period of the United States. Proceedings of the Academy of Natural 

Sciences of Philadelphia, 20:184–194. [Presented 28 July 1868, issued 1869.]

Cope, E. D. 1869. Third Contribution to the Fauna of the Miocene Period of the 

United States. Proceedings of the Academy of Natural Sciences of Philadelphia, 21:6–12.

Cope, E. D. 1895. Fourth Contribution to the Marine Fauna of the Miocene Period of the United States. Proceedings of the American Philosophical Society, 

34:135–155.

Cranford, T. W. 1999. The Sperm Whale’s Nose: Sexual Selection on a 

Grand Scale? Marine Mammals Science, 15:1133–1157. https://doi.

org/10.1111/j.1748-7692.1999.tb00882.x

Cranford, T. W., P. Krysl, and M. Amundin. 2010. A New Acoustic Portal into the 

Odontocete Ear and Vibrational Analysis of the Tympanoperiotic Complex. 

PloS ONE, 5:1–29. https://doi.org/10.1371/journal.pone.0011927

Cremer, M. J., and P. C. Simões-Lopes. 2005. The Occurrence of Pontoporia blainvillei (Gervais & d’Orbigny) (Cetacea, Pontoporiidae) in an Estuarine Area 

in Southern Brazil. Revista Brasileira de Zoologia, 22:717–723. https://doi.

org/10.1590/S0101-81752005000300032

Crespo, E. A. 2002. Franciscana, Pontoporia blainvillei. In Encyclopedia of Marine 

Mammals, ed. W. F. Perrin, B. Wursig, and J. G. M. Thewissen, pp. 482–485. 

San Diego, Calif.: Academic Press.

Dal Piaz, G. 1904. Neosqualodon, Nuovo Genere Della Famiglia Degli Squalodontidi. Mémoires de la Société Paléontologique Suisse, 31:1–19.

Dal Piaz, G. 1916. Gli Odontoceti del Miocene Bellunese. Introduzione Generale. 

Memorie dell’Istituto Geologico della Università di Padova, 5:i–vii.
182 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Dawson, S. D. 1996a. A Description of the Skull and Postcrania of Hadrodelphis 

calvertense Kellogg 1966, and Its Position within the Kentriodontidae (Cetacea; Delphinoidea). Journal of Vertebrate Paleontology, 16:125–134. https://

doi.org/10.1080/02724634.1996.10011290

Dawson, S. D. 1996b. A New Kentriodontid Dolphin (Cetacea; Delphinoidea) 

from the Middle Miocene Choptank Formation, Maryland. Journal of Vertebrate Paleontology, 16:135–140. https://doi.org/10.1080/02724634.1996

.10011291

Dawson, S. D. 2002. Kentriodontidae. In Encyclopedia of Marine Mammals, ed. 

W. F. Perrin, H. Thewissen, and B. Wursig, pp. 663–666. San Diego, Calif.: 

Academic Press.

Dawson, S. D., D. J. Bohaska, R. E. Fordyce, and H. Ichishima. 1996. The Kentriodontidae and the Origin of the Delphinoids. In Abstracts of Papers, 

Sixth North American Paleontological Convention, Smithsonian Institution, 

Washington, D.C., June 9–June 12, 1996. Paleontological Society Special 

Publications, 8:99. https://doi.org/10.1017/S2475262200001015

Dawson, S. D., and M. D. Gottfried. 2002. Paleopathology in a Miocene Kentriodontid Dolphin (Cetacea: Odontoceti). In Cenozoic Mammals of Land and 

Sea: Tributes to the Career of Clayton E. Ray, ed. R. J. Emry, pp. 263–270. 

Smithsonian Contributions to Paleobiology 93. Washington, D.C.: Smithsonian Institution Press.

de Verteuil, L., and G. Norris. 1996. Miocene Dinoflagellate Stratigraphy and Systematics of Maryland and Virginia. Micropaleontology, 42(Suppl.):1–172. 

https://doi.org/10.2307/1485926

Di Celma, C., E. Malinverno, G. Bosio, A. Collareta, K. Gariboldi, A. Gioncada, G. 

Molli, D. Basso, R. M. Varas-Malca, P. P. Pierantoni, I. M. Villa, O. Lambert, 

W. Landini, G. Sarti, G. Cantalamessa, M. Urbina, and G. Bianucci. 2017. 

Sequence Stratigraphy and Paleontology of the Upper Miocene Pisco Formation along the Western Side of the Lower Ica Valley (Ica Desert, Peru). Rivista 

Italiana di Paleontologia e Stratigrafia, 123:255–273.

Di Celma, C., P. Pierantoni, E. Malinverno, A. Collareta, O. Lambert, W. Landini, 

G. Bosio, K. Gariboldi, A. Gioncada, C. de Muizon, G. Molli, F. G. Marx, R. 

M. Varas-Malca, M. Urbina, and G. Bianucci. 2019. Allostratigraphy and Paleontology of the Lower Miocene Chilcatay Formation in the Zamaca Area, 

East Pisco Basin, Southern Peru. Journal of Maps, 15:393–405. https://doi.or

g/10.1080/17445647.2019.1604439

Dooley, A. C., Jr., 2003. A Review of the Eastern North American Squalodontidae 

(Mammalia, Cetacea). Jeffersoniana, 11:1–26.

Dooley, A. C., Jr., 2005. A New Species of Squalodon (Mammalia, Cetacea) from 

the Middle Miocene of Eastern North America. Virginia Museum of Natural 

History Memoir 8. Martinsville: Virginia Museum of Natural History.

du Bus, B. A. L. 1867. Sur Quelques Mammifères du Crag d’Anvers. Bulletin de 

l’Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique, 

24:562–577.

du Bus, B. A. L. 1868. Sur Différents Ziphiides Nouveaux du Crag d’Anvers. Bulletin de l’Académie Royale des Sciences de Belgique, 25:621–630.

du Bus, B. A. L. 1872. Mammifères Nouveaux du Crag d’Anvers. Bulletin de 

l’Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique,

34:491–509.

Eastman, C. R. 1906. Sharks’ Teeth and Cetacean Bones. Bulletin of the Museum 

of Comparative Zoology, 50:75–98.

Eastman, C. R. 1907. Type and Fossil Cetaceans in the Museum of Comparative 

Zoology. Bulletin of the Museum of Comparative Zoology, 51:79–94.

Feldman, R. M. 1989. Whitening Fossils for Photographic Purposes. In Paleotechniques, ed. R. M. Feldman. Paleontological Society Special Publications, 

4:342–346. https://doi.org/10.1017/S2475262200005323

Flores-Trujillo, J. G., F. J. Aranda-Manteca, and L. G. Barnes. 2000. Identificación 

del Delfín Fósil del Mioceno Medio, Liolithax kernensis Kellogg 1931. [The 

Identity of the Fossil Middle Miocene Dolphin, Liolithax kernensis Kellogg 

1931.] Paper presented at XXV Reunión Internacional para el Estudio de los 

Mamíferos Marinos, Sociedad Mexicana para el Estudio de los Mamíferos 

Marinos, La Paz, Mexico, 7–11 May.

Flower, W. H. 1867. Description of the Skeleton of Inia geoffrensis and of the Skull 

of Pontoporia blainvillei, with Remarks on the Systematic Position of These 

Animals in the Order Cetacea. Transactions of the Zoological Society of London, 6(3):87–116. https://doi.org/10.1111/j.1096-3642.1867.tb00572.x

Fordyce, R. E. 1994. Waipatia maerewhenua, New Genus and New Species 

(Waipatiidae, New Family), an Archaic Late Oligocene Dolphin (Cetacea: 

Odontoceti: Platanistoidea) from New Zealand. Proceedings of the San Diego Society of Natural History, 29:147–176. https://doi.org/10.5962/bhl.

part.10662

Fordyce, R. E. 2002. Simocetus rayi (Odontoceti: Simocetidae) (New Species, New 

Genus, New Family), a Bizarre New Archaic Oligocene Dolphin from the 

Eastern North Pacific. In Cenozoic Mammals of Land and Sea: Tributes to 

the Career of Clayton E. Ray, ed. R. J. Emry, pp. 185–222. Smithsonian 

Contributions to Paleobiology 93. Washington, D.C.: Smithsonian Institution Press.

Fordyce, R. E. 2009a. Cetacean Evolution. In Encyclopedia of Marine Mammals, 

2nd ed., ed. W. F. Perrin, H. Thewissen, and B. Wursig, pp. 201–207. San 

Diego, Calif.: Academic Press. https://doi.org/10.1016/B978-0-12-373553-

9.00053-5

Fordyce, R. E. 2009b. Cetacean Fossil Record. In Encyclopedia of Marine Mammals, 2nd ed., ed. W. F. Perrin, H. Thewissen, and B. Wursig, pp. 207–215. 

San Diego, Calif.: Academic Press. https://doi.org/10.1016/B978-0-12-

373553-9.00054-7

Fordyce, R. E., and C. de. Muizon. 2001. Evolutionary History of Cetaceans: A 

Review. In Secondary Adaptation of Tetrapods to Life in Water, ed. J.-M. 

Mazin, and V. de Buffrénil, pp. 169–233. Munich: Verlag Dr. Friedrich Pfeil.

Fordyce, R. E., G. Aguirre-Fernández, C. Loch, and Y. Tanaka. 2013. Tusks in Extinct Oligocene Dolphins: Feeding, Display, Agonism, or Sensory? Abstracts, 

20th Biennial Conference on the Biology of Marine Mammals 2013 (Society 

of Marine Mammalogy): 71.

Fraser, F. C., and P. E. Purves. 1960. Hearing in Cetaceans: Evolution of the Accessory Air Sacs and the Structure of the Outer and Middle Ear in Recent Cetaceans. Bulletin of the British Museum (Natural History), Zoology, 7:1–140. 

https://doi.org/10.5962/p.314160

Fuller, A. J., and S. J. Godfrey, 2007. A Late Miocene Ziphiid (Messapicetus

sp.: Odontoceti: Cetacea) from the St. Marys Formation of Calvert Cliffs, 

Maryland. Journal of Vertebrate Paleontology, 27:535–540. https://doi.

org/10.1671/0272-4634(2007)27[535:ALMZMS]2.0.CO;2

Gaetán, C. M., M. R. Buono, and L. C. Gaetano. 2019. Prosqualodon australis (Cetacea: Odontoceti) from the Early Miocene of Patagonia, Argentina: 

Redescription and Phylogenetic Analysis. Ameghiniana, 56:1–27. https://doi.

org/10.5710/AMGH.21.11.2018.3208

Galatius, A., and C. C. Kinze. 2003. Ankylosis Patterns in the Postcranial Skeleton 

and Hyoid Bones of the Harbour Porpoise (Phocoena phocoena) in the Baltic 

and North Sea. Canadian Journal of Zoology, 81:1851–1861. https://doi.

org/10.1139/z03-181

Geisler, J. H., S. J. Godfrey, and O. Lambert. 2012. A New Genus and Species of 

Late Miocene Inioid (Cetacea: Odontoceti) from the Meherrin River, North 

Carolina, U.S.A. Journal of Vertebrate Paleontology, 32:198–211. https://

doi.org/10.1080/02724634.2012.629016

Gerholdt, J. M., and S. J. Godfrey. 2010. Enigmatic Osteology in Miocene Odontocete Rostra Suggests Periostitis. Marine Mammal Science, 26:381–394. 

https://doi.org/10.1111/j.1748-7692.2009.00342.x

Gervais, P. 1853. Description de Quelques Espèces de Phoques et de Cétacés. Annales des Sciences Naturelles, Paris, Zoologie, 20:281–292.

Gervais, P. 1861. Sur Différentes Espèces de Vertébrés Fossiles Observés pour la 

Plupart dans le Midi de la France. Mémoires de l’Académie des Sciences et 

des Lettres de Montpellier, 16:117–132.

Gervais, F. L. P., and A. d’Orbigny. 1844. M. Paul Gervais, au Nom de M. Alcide D’Orbigny et au Sien, Met Sous les Yeux de la Societé Trios Planches 

Représentent des Dauphins Observés par ce Dernier Pendant Son Voyage 

dans l’Amerique Méridionale. Bulletin de la Société Philomathique de Paris, 

extraits des Procès-Verbaux des Séances, 1844:38–40.

Gibson, M. L., and J. H. Geisler. 2009. A New Pliocene Dolphin (Cetacea: Pontoporiidae), from the Lee Creek Mine, North Carolina. Journal of Vertebrate 

Paleontology, 29:966–971. https://doi.org/10.1671/039.029.0307

Gibson, T. G. 1983. Key Foraminifera from Upper Oligocene to Lower Pleistocene 

Strata of the Central Atlantic Coastal Plain. In Geology and Paleontology of 

the Lee Creek Mine, North Carolina, I, ed. C. E. Ray, pp. 355–453. Smithsonian Contributions to Paleobiology 53. Washington, D.C.: Smithsonian 

Institution Press.

Gilbert, K. N., L. C. Ivany, and M. D. Uhen. 2018. Living Fast and Dying Young: 

Life History and Ecology of a Neogene Sperm Whale, Journal of Vertebrate 

Paleontology, 38:e1439038. https://doi.org/10.1080/02724634.2018.14390

38

Gill, T. 1871. Synopsis of the Primary Subdivisions of the Cetaceans. Communications of the Essex Institute, 6:121–126.

Ginsburg, L., and P. Janvier. 1971. Les Mammifères Marins des Faluns Miocènes de 

la Touraine et de l’Anjou. Bulletin du Muséum National d’Histoire Naturelle, 

Paris, 22:161–195.
NUMBER 107 • 183

Godfrey, S. J. 2013. On the Olfactory Apparatus in the Miocene Odontocete Squalodon sp. (Squalodontidae). Comptes Rendus Palevol, 12:519–530. https://

doi.org/10.1016/j.crpv.2013.03.002

Godfrey, S. J., and L. G. Barnes. 2008. A New Genus and Species of Late Miocene 

Pontoporiid Dolphin (Cetacea: Odontoceti) from the St. Marys Formation 

in Maryland. Journal of Vertebrate Paleontology, 28:520–528. https://doi.

org/10.1671/0272-4634(2008)28[520:ANGASO]2.0.CO;2

Godfrey, S. J., L. G. Barnes, and O. Lambert. 2017. The Early Miocene Odontocete Araeodelphis Natator Kellogg, 1957 (Cetacea; Platanistidae), from the 

Calvert Formation of Maryland, U.S.A. Journal of Vertebrate Paleontology, 

37:e1278607. https://doi.org/10.1080/02724634.2017.1278607

Godfrey, S. J., M. Ellwood, S. Groff, and M. S. Verdin. 2018. Carcharocles-Bitten Odontocete Caudal Vertebrae from the Coastal Eastern United States. 

Acta Palaeontologica Polonica, 63:463–468. https://doi.org/10.4202/

app.00495.2018

Gottfried, M. D., D. J. Bohaska, and F. C. Whitmore Jr. 1994. Miocene Cetaceans 

of the Chesapeake Group. In Contributions in Marine Mammal Paleontology 

Honoring Frank C. Whitmore, Jr., ed. A. Berta and T. A. Deméré. Proceedings of the San Diego Society of Natural History, 29:229–238.

Grateloup, J. P. S. 1840. Description d’un Fragment de Mâchoire Fossile, d’un Genre 

Nouveau de Reptile (Saurien), de Taille Gigantesque, Voisin del’Iguanodon, 

Trouvé dans le Grès Marin, à Léognan, près Bordeaux. Actes de l’Academie 

national des sciences, belles-lettres et artes de Bordeaux, 2:201–210.

Gray, J. E. 1821. On the Natural Arrangement of Vertebrose Animals. London 

Medical Repository Monthly Journal and Review, 15:296–310.

Gray, J. E. 1846. On the Cetaceous Animals. In The Zoology of the Voyage of 

H.M.S. Erebus and Terror under the Command of Captain Sir James Clark 

Ross, during the Years 1839 to 1843, ed. J. Richardson and J. E. Gray, vol. 1, 

pp. 13–53. London: Longman, Brown, Green, and Longmans.

Gray, J. E. 1850. Catalogue of the Specimens of Mammalia in the Collections of the 

British Museum. Part 1: Cetacea. London: British Museum.

Gray, J. E. 1863. On the Arrangement of the Cetaceans. Proceedings of the Zoological Society of London, 1863:197–202.

Gray, J. E. 1865. Notices of a New Genus of Delphinoid Whales from the Cape 

of Good Hope, and of Other Cetaceans from the Same Seas. Proceedings of the Zoological Society of London, 1865:522–529. https://doi.

org/10.1111/j.1469-7998.1865.tb02385.x

Gray J. E. 1868. Synopsis of the Species of Whales and Dolphins in the Collection 

of the British Museum. London: Bernard Quaritch.

Guo, Z., and N. Kohno. 2021. A New Kentriodontid (Cetacea: Odontoceti) from 

the Early to Middle Miocene of the Western North Pacific and a Revision 

of Kentriodontid Phylogeny. PeerJ, 9:e10945. https://doi.org/10.7717/

peerj.10945

Harlan, R. 1842. Description of a New Extinct Species of Dolphin from Maryland. 

Bulletin and Proceedings of the National Institute for the Promotion of Science, Washington, D.C., 2:195–196.

Hay, O. P. 1902. Bibliography and Catalogue of the Fossil Vertebrata of North 

America. Bulletin of the United States Geological Survey, 179:1–868. https://

doi.org/10.5962/bhl.title.20094

Holl, F. 1829. Handbuch der Petrefactenkunde. Eine Beschreibung aller bis jetzt 

bekannten Versteinerungen aus dem Thier- und Pflanzenreiche / von Friedrich Holl. Mit einer Einleitung über die Vorwelt der organischen Wesen auf 

der Erde von Dr. Ludwig Choulant. Volume 1. Quedlinburg und Leipzig : 

Ernst’schen Buchhandlung [1843].

Hooker, S. K. 2001. Marine Mammals: Sperm Whales and Beaked Whales. In 

The Encyclopedia of Ocean Sciences, ed. J. Steele, S. Thorpe, and K. Turekian, pp. 2863–2870. London: Academic Press. https://doi.org/10.1006/

rwos.2001.0430

Ichishima, H. 1993. Fossil Dolphin from the Middle Miocene Takinoue Formation at Hobetsu-cho, Hokkaido, Japan. Bulletin of the Hobetsu Museum, 

9:37–44.

Ichishima, H. 1994. A New Fossil Kentriodontid Dolphin (Cetacea; Kentriodontidae) from the Middle Miocene Takinone Formation, Hokkaido, Japan. Island Arc, 3:473–485. https://doi.org/10.1111/j.1440-1738.1994.tb00126.x

Ichishima, H. 2016. The Ethmoid and Presphenoid of Cetaceans. Journal of Morphology, 277:1661–1674. https://doi.org/10.1002/jmor.20615

Ichishima, H., L. G. Barnes, R. E. Fordyce, M. Kimura, and D. J. Bohaska. 1994. 

A Review of Kentriodontine Dolphins (Cetacea; Delphinoidea; Kentriodontidae): Systematics and Biogeography. Island Arc, 3:486–492. https://doi.

org/10.1111/j.1440-1738.1994.tb00127.x

International Commission on Zoological Nomenclature. 1999. International Code 

of Zoological Nomenclature. 4th ed. London: International Trust for Zoological Nomenclature and the British Museum.

Jacobs, D. K., T. A. Haney, and K. D. Louie. 2004. Genes, Diversity, and Geological Process on the Pacific Coast. Annual Review of Earth and Planetary 

Science, 32:601–652.

Kasuya, T. 1973. Systematic Consideration of Recent Toothed Whales Based on 

the Morphology of Tympano-Periotic Bone. Scientific Reports of the Whales 

Research Institute, Tokyo, 25:1–103.

Kazár, E. 2002. Revised Phylogeny of the Physeteridae (Mammalia: Cetacea) in the 

Light of Placoziphius Van Beneden, 1869 and Aulophyseter Kellogg, 1927. 

Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Sciences de 

la Terre, 72:151–170.

Kazár, E. 2005. A New Kentriodontid (Cetacea: Delphinoidea) from the Middle Miocene of Hungary. Mitteilungen aus dem Museum für Naturkunde 

Berlin, Geowissenschaftliche Reihe, 8:53–73. https://doi.org/10.1002/

mmng.200410004

Kazár, E. 2006. Sophianaecetus, a Replacement Name for Mediocris (Cetacea: Delphinoidea: Kentriodontidae). Fossil Record, 9(2):260 https://doi.

org/10.5194/fr-9-260-2006

Kazár, E., and D. Grigorescu. 2005. Revision of Sarmatodelphis moldavicus Kirpichnikov, 1954 (Cetacea: Delphinoidea), from the Miocene of Kishinev, Republic of Moldavia. Journal of Vertebrate Paleontology, 25:929–935. https://

doi.org/10.1671/0272-4634(2005)025[0929:ROSMKC]2.0.CO;2

Kazár, E., and O. Hampe. 2014. A New Species of Kentriodon (Mammalia, 

Odontoceti, Delphinoidea) from the Middle/Late Miocene of Groß Pampau 

(Schleswig-Holstein, North Germany). Journal of Vertebrate Paleontology, 

34:1216–1230. https://doi.org/10.1080/02724634.2014.857347

Kellogg, R. 1923a. Description of Two Squalodonts Recently Discovered in the 

Calvert Cliffs, Maryland; and Notes on the Shark Toothed Cetaceans. 

Proceedings of the United States National Museum, 62:1–69. https://doi.

org/10.5479/si.00963801.62-2462.1

Kellogg, R. 1923b. Description of an Apparently New Toothed Cetacean from 

South Carolina. Smithsonian Miscellaneous Collections, 76:1–7.

Kellogg, R. 1924a. A Fossil Porpoise from the Calvert Formation of Maryland. 

Proceedings of the United States National Museum, 63:1–39. https://doi.

org/10.5479/si.00963801.63-2482.1

Kellogg, R. 1924b. Tertiary Pelagic Mammals of Eastern North America. Bulletin 

of the Geological Survey of America, 35:755–766. https://doi.org/10.1130/

GSAB-35-755

Kellogg, R. 1925a. On the Occurrence of Remains of Fossil Porpoises of the Genus 

Eurhinodelphis in North America. Proceedings of the United States National 

Museum, 66:26. https://doi.org/10.5479/si.00963801.66-2563.1

Kellogg, R. 1925b. A Fossil Physeteroid Cetacean from Santa Barbara County, California. Proceedings of the United States National Museum, 66:27. https://

doi.org/10.5479/si.00963801.66-2564.1

Kellogg, R. 1925c. Two Fossil Physeteroid Whales from California. Contributions 

to Palaeontology from the Carnegie Institution of Washington, 348:1–34. 

https://doi.org/10.5479/si.00963801.66-2564.1

Kellogg, R. 1926. Supplementary Observations on the Skull of the Fossil Porpoise 

Zarhachis flagellator Cope. Proceedings of the United States National Museum, 67:1–18. https://doi.org/10.5479/si.00963801.67-2600.1

Kellogg, R. 1927a. Kentriodon pernix, a Miocene Porpoise from Maryland. 

Proceedings of the United States National Museum, 69:1–55. https://doi.

org/10.5479/si.00963801.69-2645.1

Kellogg, R. 1927b. Study of the Skull of a Fossil Sperm-Whale from the Temblor 

Miocene of Southern California. Publications of the Carnegie Institution of 

Washington, 346:1–23.

Kellogg, R. 1928. History of Whales—Their Adaptation to Life in the Water. Quarterly Review of Biology, 3:29–76, 174–208. https://doi.org/10.1086/394300

Kellogg, R. 1931. Pelagic Mammals from the Temblor Formation of the Kern 

River Region, California. Proceedings of the California Academy of Sciences, 

19:217–397.

Kellogg, R. 1932. A Miocene Long-Beaked Porpoise from California. Smithsonian 

Miscellaneous Collections, 87:1–11.

Kellogg, R. 1955. Three Miocene Porpoises from Calvert Cliffs, Maryland. Proceedings of the United States National Museum, 105:101–154. https://doi.

org/10.5479/si.00963801.105-3354.101

Kellogg, R. 1957. Two Additional Miocene Porpoises from the Calvert Cliffs, 

Maryland. Proceedings of the United States National Museum, 107:279–

337. https://doi.org/10.5479/si.00963801.108-3387.279
184 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Kellogg, R. 1959. Description of the Skull of Pomatodelphis inaequalis Allen. Bulletin of the Museum of Comparative Zoology, 121:1–26, plates 1–6.

Kellogg, R. 1965. Fossil Marine Mammals from the Miocene Calvert Formation of 

Maryland and Virginia. Part 2. The Miocene Calvert Sperm Whale Orycterocetus. United States National Museum Bulletin, 247:47–63.

Kellogg, R. 1966. Fossil Marine Mammals from the Miocene Calvert Formation 

of Maryland and Virginia. 4. A New Odontocete from the Calvert Miocene 

of Maryland. United States National Museum Bulletin, 247:99–101, plates 

44–45.

Kidwell, S. M. 1984. Outcrop Features and Origin of Basin Margin Unconformities 

in the Lower Chesapeake Group (Miocene), Atlantic Coastal Plain. In Interregional Unconformities and Hydrocarbon Accumulation, ed. J. S. Schlee. 

American Association of Petroleum Geologists Memoir, 36:37–58. https://

doi.org/10.1306/M36440C3

Kidwell, S. M. 1989. Stratigraphic Condensation of Marine Transgressive Records: 

Origin of Major Shell Deposits in the Miocene of Maryland. Journal of Geology, 97:1–24. https://doi.org/10.1086/629278

Kidwell, S. M. 1997. Anatomy of Extremely Thin Marine Sequences Landward 

of a Passive-Margin Hinge Zone: Neogene Calvert Cliffs Succession, Maryland, U.S.A. Journal of Sedimentary Research, 67(2):322–240. https://doi.

org/10.1306/D4268563-2B26-11D7-8648000102C1865D

Kidwell, S. M., D. S. Powars, L. E. Edwards, and P. R. Vogt. 2015. Miocene Stratigraphy and Paleoenvironments of the Calvert Cliffs, Maryland. In Tripping 

from the Fall Line: Field Excursions for the GSA Annual Meeting, Baltimore, 

2015, ed. D. K. Brezinski, J. P. Halka, and R. A. Ortt Jr., pp. 231–279. Geological Society of America Field Guide 40. Boulder, Colo.: Geological Society 

of America. https://doi.org/10.1130/2015.0040(08)

Kimura, T. 2019. First Squalodelphinid from the Early Miocene of the Pacific 

Realm in the Northern Hemisphere. Journal of Vertebrate Paleontology, 38. 

https://doi.org/10.1080/02724634.2018.1493595

Kimura, T., and Y. Hasegawa. 2019. A New Species of Kentriodon (Cetacea, Odontoceti, Kentriodontidae) from the Miocene of Japan. Journal of Vertebrate 

Paleontology, 39:e1566739. https://doi.org/10.1080/02724634.2019.15667

39

Kirpichnikov, A. A. 1954. Dva Novykh Roda Delfinov iz Sarmata SSSR. Trudy 

Paleontologicheskogo Instituta, 47:181–190.

Lambert, O. 2004. Systematic Revision of the Miocene Long-Snouted Dolphin 

Eurhinodelphis longirostris du Bus, 1872 (Cetacea, Odontoceti, Eurhinodelphinidae). Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, 

Sciences de la Terre, 74:147–174.

Lambert, O. 2005a. Review of the Miocene Long-Snouted Dolphin Priscodelphinus cristatus du Bus, 1872 (Cetacea, Odontoceti) and Phylogeny among Eurhinodelphinids. Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, 75:211–235.

Lambert, O. 2005b. Systematics and Phylogeny of the Fossil Beaked Whales Ziphirostrum du Bus, 1868 and Choneziphius Duvernoy, 1851 (Cetacea, Odontoceti), from the Neogene of Antwerp (North of Belgium). Geodiversitas, 

27:443–497.

Lambert, O. 2005c. Phylogenetic Affinities of the Long-Snouted Dolphin Eurhinodelphis (Cetacea, Odontoceti) from the Miocene of Antwerp. Palaeontology, 

48:653–679. https://doi.org/10.1111/j.1475-4983.2005.00472.x

Lambert, O. 2006. First Record of a Platanistid (Cetacea, Odontoceti) in the North 

Sea Basin: A Review of Cyrtodelphis Abel, 1899 from the Miocene of Belgium. Oryctos, 6:69–79.

Lambert, O. 2008. Sperm Whales from the Miocene of the North Sea: A Re-appraisal. Bulletin del’Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre, 78:277–316.

Lambert, O., C. Auclair, C. Cauxeiro, M. Lopez, and S. Adnet. 2018a. A Close 

Relative of the Amazon River Dolphin in Marine Deposits: A New Iniidae 

from the Late Miocene of Angola. PeerJ, 6:e5556. https://doi.org/10.7717/

peerj.5556

Lambert, O., and G. Bianucci. 2019. How to Break a Sperm Whale’s Teeth: Dental 

Damage in a Large Miocene Physeteroid from the North Sea Basin. Journal 

of Vertebrate Paleontology, 39:e1660987. https://doi.org/10.1080/0272463

4.2019.1660987

Lambert, O., G. Bianucci, and C. de Muizon. 2017a. Macroraptorial Sperm Whales 

(Cetacea, Odontoceti, Physeteroidea) from the Miocene of Peru. Zoological Journal of the Linnean Society, 179:404–474. https://doi.org/10.1111/

zoj.12456

Lambert, O., G. Bianucci, and K. Post. 2009. A New Beaked Whale (Odontoceti, 

Ziphiidae) from the Middle Miocene of Peru. Journal of Vertebrate Paleontology, 29:910–922. https://doi.org/10.1671/039.029.0304

Lambert, O., G. Bianucci, K. Post, C. Muizon, de, R. Salas-Gismondi, M. Urbina, 

and J. Reumer. 2010a. The Giant Bite of a New Raptorial Sperm Whale from 

the Miocene Epoch of Peru. Nature, 466:105–108. https://doi.org/10.1038/

nature09067

Lambert, O., G. Bianucci, and M. Urbina. 2014. Huaridelphis raimondii, a New 

Early Miocene Squalodelphinidae (Cetacea, Odontoceti) from the Chilcatay 

Formation, Peru. Journal of Vertebrate Paleontology, 34:987–1004. https://

doi.org/10.1080/02724634.2014.858050

Lambert, O., G. Bianucci, M. Urbina, and J. H. Geisler. 2017b. A New Inioid (Cetacea, Odontoceti, Delphinida) from the Miocene of Peru and the Origin of 

Modern Dolphin and Porpoise Families. Zoological Journal of the Linnean 

Society, 179:919–946.

Lambert, O., A. Collareta, A. Benites-Palomino, C. Di Celma, C. Muizon, de, M. 

Urbina, and G. Bianucci. 2020. A New Small, Mesorostrine Inioid (Cetacea, 

Odontoceti, Delphinida) from Four Upper Miocene Localities in the Pisco 

Basin, Peru. Papers in Palaeontology, 7:1043–1064. https://doi.org/10.1002/

spp2.1332

Lambert, O., A. Collareta, W. Landini, K. Post, B. Ramassamy, C. Di Celma, M. 

Urbina, and G. Bianucci. 2015a. No Deep Diving: Evidence of Predation on 

Epipelagic Fish for a Stem Beaked Whale from the Late Miocene of Peru. 

Proceedings of the Royal Society B, 282:20151530. https://doi.org/10.1098/

rspb.2015.1530

Lambert, O., C. de Muizon, and G. Bianucci. 2015b. A New Archaic Homodont 

Toothed Cetacean (Mammalia, Cetacea, Odontoceti) from the Early Miocene 

of Peru. Geodiversitas, 37:79–108. https://doi.org/10.5252/g2015n1a4

Lambert, O., C. de Muizon, G. Duhamel, and J. van der Plicht. 2018b. Neogene 

and Quaternary Fossil Remains of Beaked Whales (Cetacea, Odontoceti, 

Ziphiidae) from Deep-Sea Deposits off Crozet and Kerguelen Islands, Southern Ocean. Geodiversitas, 40:135–160. https://doi.org/10.5252/geodiversitas2018v40a6

Lambert, O., C. de Muizon, E. Malinverno, C. D. Celma, M. Urbina, and G. Bianucci. 2017c. A New Odontocete (Toothed Cetacean) from the Early Miocene of Peru Expands the Morphological Disparity of Extinct Heterodont 

Dolphins. Journal of Systematic Palaeontology, 1–36. https://doi.org/10.108

0/14772019.2017.1359689

Lambert, O., M. Estevens, and R. Smith. 2005. A New Kentriodontine Dolphin 

from the Middle Miocene of Portugal. Acta Palaeontologica Polonica, 

50:239–248.

Lambert, O., S. J. Godfrey, and E. M. G. Fitzgerald. 2019. Yaquinacetus meadi, a 

New Latest Oligocene–Early Miocene Dolphin (Cetacea, Odontoceti, Squaloziphiidae, fam. nov.) from the Nye Mudstone (Oregon, USA). Journal of 

Vertebrate Paleontology, 38:e1559174. https://doi.org/10.1080/02724634.2

018.1559174

Lambert, O., S. J. Godfrey, and A. J. Fuller. 2010b. A Miocene Ziphiid (Cetacea: 

Odontoceti) from Calvert Cliffs, Maryland, U.S.A. Journal of Vertebrate Paleontology, 30:1645–1651. https://doi.org/10.1080/02724634.2010.501642

Lambert, O., and S. Goolaerts. 2022. Late Miocene Survival of a Hyper-Longirostrine Dolphin and the Neogene to Recent Evolution of Rostrum Proportions among Odontocetes. Journal of Mammalian Evolution, 29:99–111. 

https://doi.org/10.1007/s10914-021-09573-6

Lambert, O., and S. Louwye. 2006. Archaeoziphius microglenoideus, a New Primitive Beaked Whale (Mammalia, Cetacea, Odontoceti) from the Middle Miocene of Belgium. Journal of Vertebrate Paleontology, 26:182–191. https://

doi.org/10.1671/0272-4634(2006)26[182:AMANPB]2.0.CO;2

Lambert, O., J. Schlögl, and M. Kováč. 2008. Middle Miocene Toothed Whale 

with Platanista-Like Teeth from the Vienna Basin (Western Carpathians, 

Slovakia). Neues Jahrbuch für Geologie und Paläontologie, 250:157–166. 

https://doi.org/10.1127/0077-7749/2008/0250-0157

Lee, Y.-N., H. Ichishima, and D. K. Choi. 2012. First Record of a Platanistoid 

Cetacean from the Middle Miocene of South Korea. Journal of Vertebrate 

Paleontology, 32:231–234. https://doi.org/10.1080/02724634.2012.626005

Leidy, J. 1853. Observations on Extinct Cetacea. Proceedings of the Academy of 

Natural Sciences, 6:377–378.

Leidy, J. 1869. The Extinct Mammalian Fauna of Dakota and Nebraska, Including 

an Account of Some Allied Forms from Other Localities, Together with a 

Synopsis of the Mammalian Remains of North America. Journal of the Academy of Natural Sciences of Philadelphia, 2:1–472. https://doi.org/10.5962/

bhl.title.20910

Leidy, J. 1877. Description of Vertebrate Remains, Chiefly from the Phosphate 

Beds of South Carolina. Journal of the Academy of Natural Sciences of Philadelphia, 8:209–261.
NUMBER 107 • 185

Lockyer, C. H., and G. T. Braulik. 2014. An evaluation of age estimation using 

teeth from South Asian River Dolphins (Platanistidae). NAMMCO Scientific 

Publications, 10. https://doi.org/10.7557/3.3268

Louwye, S., J. De Coninck, and J. Verniers. 2000. Shallow Marine Lower and 

Middle Miocene Deposits at the Southern Margin of the North Sea Basin 

(Northern Belgium): Dinoflagellate Cyst Biostratigraphy and Depositional 

History. Geological Magazine, 137:381–394. https://doi.org/10.1017/

S0016756800004258

Lydekker, R. 1893. Contribution to the Knowledge of the Fossil Vertebrates of 

Argentina. Part II. Cetacean Skulls from Patagonia. Anales del Museo de La 

Plata, 1893:1–14.

Marx, F. G., J. Albers, and B. Berning. 2011. Lost in Translation—A History of 

Systematic Confusion and Comments on the Type Species of Squalodon and 

Patriocetus (Cetacea, Odontoceti). Palaeontology, 54:303–307. https://doi.

org/10.1111/j.1475-4983.2010.01018.x

Marx, F. G., and R. E. Fordyce. 2015. Baleen Boom and Bust: A Synthesis of 

Mysticete Phylogeny, Diversity and Disparity. Royal Society Open Science, 

2:140434. https://doi.org/10.1098/rsos.140434

Marx, F. G., O. Lambert, and M. D. Uhen. 2016. Cetacean Paleobiology. Chichester, UK: John Wiley. https://doi.org/10.1002/9781118561546

McCurry, M. R., and N. D. Pyenson. 2018. Hyper-Longirostry and Kinematic 

Disparity in Extinct Toothed Whales. Paleobiology, 45:21–29. https://doi.

org/10.1017/pab.2018.33

Mchedlidze, G. A. 1976. Osnovnye Cherty Paleobiologicheskoi Istorii Kitoobraznykh. [General Features of the Palaeobiological Evolution of Cetacea.] 

Tbilisi: Metsniereba Publishers. [English translation, Amerind Publishing, 

New Delhi, 1984.]

McLeod, C. D. 2018. Beaked Whales, Overview. In Encyclopedia of Marine Mammals, 3rd ed., ed. B. Würsig, J. G. M. Thewissen, and K. M. Kovacs, pp. 80–

83. San Diego, Calif.: Academic Press. McLeod, C. D. 2018. Beaked Whales, 

Overview. In Encyclopedia of Marine Mammals, 3rd ed., ed. B. Würsig, J. G. 

M. Thewissen, and K. M. Kovacs, pp. 80–83. San Diego, Calif.: Academic 

Press. https://doi.org/10.1016/B978-0-12-804327-1.00062-5

McLeod, C. D., W. F. Perrin, R. Pitman, J. Barlow, L. Ballance, A. D’Amico, T. Gerrodette, G. Joyce, K. D. Mullin, D. L. Palka, and G. T. Waring. 2006. Known 

and Inferred Distributions of Beaked Whale Species (Cetacea: Ziphiidae). 

Journal of Cetacean Research and Management, 7:271–286.

Mead, J. G. 1975. A Fossil Beaked Whale (Cetacea: Ziphiidae) from the Miocene of 

Kenya. Journal of Paleontology, 49:745–751.

Mead, J. G. 2009. Beaked Whales, Overview: Ziphiidae. In Encyclopedia of Marine 

Mammals, 2nd ed., ed. W. F. Perrin, B. Würsig, and J. G. M. Thewissen, pp. 

94–97. San Diego, Calif.: Academic Press. https://doi.org/10.1016/B978-0-

12-373553-9.00027-4

Mead, J. G., and R. E. Fordyce. 2009. The Therian Skull: A Lexicon with Emphasis 

on the Odontocetes. Smithsonian Contributions to Zoology 627. Washington, D.C.: Smithsonian Institution Scholarly Press. https://doi.org/10.5479/

si.00810282.627

Methner, K., M. Campani, J. Fiebig, N. Löffler, O. Kempt, and A. Mulch. 2020. 

Middle Miocene Long-Term Continental Temperature Change in and out of 

Pace with Marine Climate Records. Scientific Reports, 10:7989. https://doi.

org/10.1038/s41598-020-64743-5

Mills, A. D. 1991. Dictionary of English Place-Names. Oxford, U.K.: Oxford University Press.

Montes, C., A. Cardona, C. Jaramillo, A. Pardo, J. C. Silva, V. Valencia, C. Ayala, 

L. C. Pérez-Angel, L. A. Rodriguez-Parra, V. Ramirez, and H. Niňo. 2015. 

Middle Miocene Closure of the Central American Seaway. Science, 348:226–

229. https://doi.org/10.1126/science.aaa2815

Moran, M. M., S. Bajpai, J. C. George, R. Suydam, S. Usip, and J. G. M. Thewissen. 2015. Intervertebral and Epiphyseal Fusion in the Postnatal Ontogeny 

of Cetaceans and Terrestrial Mammals. Journal of Mammalian Evolution, 

22:93–109. https://doi.org/10.1007/s10914-014-9256-7

Moreno, F. P. 1892. Noticias Sobre Algunos Cetáceos Fósiles y Actuales de la 

República Argentina. Revista del Museo de La Plata, 3:383–400.

Morgan, G. S. 1994. Miocene and Pliocene Marine Mammal Faunas from the Bone 

Valley Formation of Central Florida. In Contributions in Marine Mammal 

Paleontology Honoring Frank C. Whitmore, Jr., ed. A. Berta and T. A. Demere. Proceedings of the San Diego Society of Natural History, 29:239–268.

Muizon, C. de. 1983. Pliopontos littoralis un Nouveau Platanistidae (Cetacea) du 

Pliocène de la Côte Péruvienne. Comptes Rendus de l’Académie des Sciences, 

Paris, ser. 2, 296:1101–1104.

Muizon, C. de. 1984. Les Vertébrés Fossiles de la Formation Pisco (Pérou). Deuxième Partie: les Odontocètes (Cetacea, Mammalia) du Pliocène Inferieur de 

Sud-Sacaco. Institut Français d’Études Andines, Mémoire, 50:1–188.

Muizon, C. de. 1985. Nouvelles Données sur le Diphylétisme des Dauphins de 

Rivière (Odontoceti, Cetacea, Mammalia). Comptes rendus de l’Académie 

des Sciences, Paris, 301:359–361.

Muizon, C. de. 1987. The Affinities of Notocetus vanbenedeni, an Early Miocene 

Platanistoid (Cetacea Mammalia) from Patagonia, Southern Argentina. 

American Museum Novitates, 2904:l–27.

Muizon, C. de. 1988a. Le Polyphylétisme des Acrodelphidae, Odontocètes Longirostres du Miocène Européen. Bulletin du Muséum National d’Histoire 

Naturelle, Paris, 10:31–88.

Muizon, C. de 1988b. Les Vertébrés Fossiles de la Formation Pisco (Pérou). 

Troisième Partie: les Odontocètes (Cetacea, Mammalia) du Miocène. Institut 

Français d’Études Andines, Mémoire, 78:1–244.

Muizon, C. de. 1988c. Les Relations Phylogénétiques des Delphinida. Annales de 

Paléontologie, 4(4):159–227.

Muizon, C. de. 1991. A New Ziphiidae (Cetacea) from the Early Miocene of Washington State USA) and Phylogenetic Analysis of the Major Groups of Odontocetes. Bulletin du Muséum National d’Histoire Naturelle, Paris, 12:279–326.

Muizon, C. de. 1994. Are the Squalodonts Related to the Platanistoids? In Contributions in Marine Mammal Paleontology Honoring Frank Whitmore, Jr.,

ed. A. Berta and T. Deméré. Proceedings of the San Diego Society of Natural 

History, 29:135–146.

Muizon, C. de, and D. P. Domning. 2002. The Anatomy of Odobenocetops (Delphinoidea, Mammalia), the Walrus-Like Dolphin from the Pliocene of Peru and 

Its Palaeobiological Implications. Zoological Journal of the Linnean Society, 

134:423–452. https://doi.org/10.1046/j.1096-3642.2002.00015.x

Myrick, A. C. 1979. Variation, Taphonomy and Adaptation of the Rhabdosteidae 

(= Eurhinodelphidae) (Odontoceti, Mammalia) from the Calvert Formation 

of Maryland and Virginia. Ph.D. diss., University of California, Los Angeles. 

Microfilm. Ann Arbor, Mich.: University Microfilms International.

Nelson, M. D., and M. D. Uhen. 2018. First Occurrence of a Squalodelphinid (Cetacea, Odontoceti) from the Early Miocene of Washington State. Journal of 

Vertebrate Paleontology, 38:e1428197. https://doi.org/10.1080/02724634.2

017.1428197

Nummela, S., T. Wägar, S. Hemilä, and T. Reuter. 1999. Scaling of the Cetacean 

Middle Ear. Hearing Research, 133:71–81. https://doi.org/10.1016/S0378-

5955(99)00054-4

Owen, R. 1889. A History of British Fossil Mammals and Birds. John Van Voorst: 

London.

Paolucci, F., M. R. Buono, M. S. Fernández, F. G. Marx, and J. I. Cuitiño. 2020a. 

Diaphorocetus poucheti (Cetacea, Odontoceti, Physeteroidea) from Patagonia, Argentina: One of the Earliest Sperm Whales. Journal of Systematic Palaeontology, 18:335–355. https://doi.org/10.1080/14772019.2019.1605544

Paolucci, F., M. S. Fernández, M. R. Buono, and J. I. Cuitiño. 2020b. ‘Aulophyseter’ rionegrensis (Cetacea: Odontoceti: Physeteroidea) from the Miocene 

of Patagonia (Argentina): A Reappraisal. Zoological Journal of the Linnean 

Society, 20:1–30. https://doi.org/10.1093/zoolinnean/zlaa137

Peredo, C. M., J. S. Peredo, and N. D. Pyenson. 2018a. Convergence on Dental 

Simplification in the Evolution of Whales. Paleobiology, 44:434–443. https://

doi.org/10.1017/pab.2018.9

Peredo, C. M., M. D. Uhen, and M. D. Nelson. 2018b. A New Kentriodontid (Cetacea: Odontoceti) from the Early Miocene Astoria Formation and a Revision 

of the Stem Delphinidan Family Kentriodontidae. Journal of Vertebrate Paleontology, 38:e1411357. https://doi.org/10.1080/02724634.2017.1411357

Perrin, W. F. 1975. Variation of Spotted and Spinner Porpoise (Genus Stenella) in 

the Eastern Pacific and Hawaii. Bulletin of the Scripps Institution of Oceanography, 21:1–206.

Pilleri, G. 1985. The Miocene Cetacea of the Belluno Sandstones (Eastern Southern 

Alps). Memorie di Scienze Geologiche, 36:1–250.

Platto, S., C. Zhang, M. K. Pine, W. Feng, L. Yang, A. Irwin, and D. Wang. 2017. 

Behavioral Laterality in Yangtze Finless Porpoises (Neophocaena asiaeorientalis asiaeorientalis). Behavioural Processes, 140:104–114. https://doi.

org/10.1016/j.beproc.2017.04.015

Post, K., O. Lambert, and G. Bianucci. 2008. First Record of Tusciziphius crispus (Cetacea, Ziphiidae) from the Neogene of the US East Coast. Deinsea, 

12:1–10.

Post, K., S. Louwye, and O. Lambert. 2017. Scaldiporia vandokkumi, a New Pontoporiid (Mammalia, Cetacea, Odontoceti) from the Late Miocene to Earliest Pliocene of the Westerschelde Estuary (the Netherlands). PeerJ, 5:e3991. 

https://doi.org/10.7717/peerj.3991
186 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Pyenson, N. D., R. B. Irmis, J. H. Lipps, L. G. Barnes, E. D. Mitchell Jr. , and S. A. 

MacLeod. 2009. Origin of a Widespread Marine Bonebed Deposited during 

the Middle Miocene Climatic Optimum. Geology, 37:519–522. https://doi.

org/10.1130/G25509A.1

Pyenson, N. D., J. Vélez-Juarbe, C. S. Gutstein, H. Little, D. Vigil, and A. O’Dea. 

2015. Isthminia panamensis, a New Fossil Inioid (Mammalia, Cetacea) from 

the Chagres Formation of Panama and the Evolution of ‘River Dolphins’ in 

the Americas. PeerJ, 3:e1227. https://doi.org/10.7717/peerj.1227

Racicot, R. A., T. A. Deméré, B. L. Beatty, and R. W. Boessenecker. 2014. Unique 

Feeding Morphology in a New Prognathous Extinct Porpoise from the Pliocene of California. Current Biology, 24:774–779. https://doi.org/10.1016/j.

cub.2014.02.031

Ray, C. E. 1976. Phoca wymani and Other Tertiary Seals (Mammalia: Phocidae) 

Described from the Eastern Seaboard of North America. Smithsonian Contributions to Paleobiology 28. Washington, D.C.: Smithsonian Institution 

Press. https://doi.org/10.5479/si.00810266.28.1

Rensberger, J. M. 1969. A New Iniid Cetacean from the Miocene of California. 

University of California Publications in Geological Sciences, 82:1–43.

Rice, D. W. 1998. Marine Mammals of the World. Systematics and Distribution.

Lawrence, Kans.: Society for Marine Mammalogy.

Rothausen, K. 1968. Die Systematische Stellung der Europäischen Squalodontidae 

(Odontoceti, Mamm.). Palaeontologische Zeischrift, 42:83–104. https://doi.

org/10.1007/BF02987130

Seagars, D. J. 1982. Jaw Structure and Functional Mechanics of Six Delphinids 

(Cetacea, Odontoceti). Master’s thesis, San Diego State University, San Diego, Calif.

Secchi, E. R. 2010. Life History and Ecology of Franciscana, Pontoporia blainvillei

(Cetacea, Pontoporiidae). In Biology, Evolution, and Conservation of River 

Dolphins within South America and Asia, ed. M. Ruiz-Garcia and J. Shostell, 

pp. 301–322. New York: Nova Science Publishers.

Shattuck, G. B. 1904. Geological and Paleontological Relations, with a Review 

of Earlier Investigations. In The Miocene Deposits of Maryland, ed. W. B. 

Clark, G. B. Shattuck, and W. H. Dall, pp. xxxiii–cxxxvii. Baltimore: Johns 

Hopkins Press.

Shelburne, E. C. H., and A. C. Thompson. 2016. Specimen Whitening: An Assessment of Methods of Ammonium Chloride Smoke Removal. Collection 

Forum, 30(1):63–72. https://doi.org/10.14351/0831-4985-30.1.63

Simpson, G. G. 1942. The Beginnings of Vertebrate Paleontology in North America. Proceedings of the American Philosophical Society, 86:130–188.

Sinha, R. K., S. K. Verma, and L. Singh. 2010. Population Status and Conservation 

of the Ganges River Dolphin (Platanista gangetica gangetica) in the Indian 

Subcontinent. In Biology, Evolution, and Conservation of River Dolphins 

within South America and Asia, ed. M. Ruiz and J. M. Shostell, pp. 419–443. 

New York: Nova Science Publishers.

Tanaka, Y., J. Abella, G. Aguirre-Fernández, M. Gregori, and R. E. Fordyce. 

2017. A New Tropical Oligocene Dolphin from Montañita/Olón, Santa 

Elena, Ecuador. PLoS ONE, 12:e0188380. https://doi.org/10.1371/journal.

pone.0188380

Tanaka, Y., and R. E. Fordyce. 2016. Papahu-Like Fossil Dolphin from Kaikoura, 

New Zealand, Helps to Fill the Early Miocene Gap in the History of Odontoceti. New Zealand Journal of Geology and Geophysics, 59:1–17. https://doi.

org/10.1080/00288306.2016.1211540

Tanaka, Y., and R. E. Fordyce. 2017. Awamokoa tokarahi, a New Basal Dolphin in 

the Platanistoidea (Late Oligocene, New Zealand). Journal of Systematic Palaeontology, 15:365–386. https://doi.org/10.1080/14772019.2016.1202339

Tazaki, K., H. Horikawa, and S. Miyazaki. 1987. Fossil Ziphiidae from HyotanGuri off Sado Island, Central Japan. Bulletin of the Sado Museum, 9:219–

223.

Tripati, A. K., C. D. Roberts, and R. A. Eagle. 2009. Coupling of CO2 and Ice Sheet 

Stability over Major Climate Transitions of the Last 20 Million Years. Science, 326:1394–1397. https://doi.org/10.1126/science.1178296

True, F. W. 1908a. On the Occurrence of Remains of Fossil Cetaceans of the Genus 

Schizodelphis in the United States, and on Priscodelphinus (?) crassangulum

Case. Smithsonian Miscellaneous Collections (Quarterly Issue), 50:449–460.

True, F. W. 1908b. On the Classification of the Cetacea. Proceedings of the American Philosophical Society, Philadelphia, 47:385–391.

True, F. W. 1912. Description of a New Fossil Porpoise of the Genus Delphinodon

from the Miocene Formation of Maryland. Journal of the Academy of Natural Sciences of Philadelphia, 2nd ser., 15:165–194, plates 17–26.

Uhen, M. D. 2004. Form, Function, and Anatomy of Dorudon atrox (Mammalia, 

Cetacea): an Archaeocete from the Middle to Late Eocene of Egypt. University of Michigan Papers on Paleontology, 34:1–222.

Uhen, M. D. 2008a. New Protocetid Whales from Alabama and Mississippi, and a 

New Cetacean Clade, Pelagiceti. Journal of Vertebrate Paleontology, 28:589–

593. https://doi.org/10.1671/0272-4634(2008)28[589:NPWFAA]2.0.CO;2

Uhen, M. D. 2008b. A New Xenorophus-Like Odontocete Cetacean from the 

Oligocene of North Carolina and a Discussion of the Basal Odontocete 

Radiation. Journal of Systematic Palaeontology, 6:433–452. https://doi.

org/10.1017/S1477201908002472

Vélez-Juarbe, J. 2017. A New Stem Odontocete from the Late Oligocene Pysht 

Formation in Washington State, USA. Journal of Vertebrate Paleontology, 

37:e1366916. https://doi.org/10.1080/02724634.2017.1366916

Velez-Juarbe, J., A. R. Wood, C. De Gracia, and A. J. W. Hendy. 2015. Evolutionary Patterns among Living and Fossil Kogiid Sperm Whales: Evidence 

from the Neogene of Central America. PLoS ONE, 10:e0123909. https://doi.

org/10.1371/journal.pone.0123909

Viglino, M., M. R. Buono, R. E. Fordyce, J. I. Cuitiño, and E. M. Fitzgerald. 2018a. 

Anatomy and Phylogeny of the Large Shark-Toothed Dolphin Phoberodon 

arctirostris Cabrera, 1926 (Cetacea: Odontoceti) from the Early Miocene of 

Patagonia (Argentina). Zoological Journal of the Linnean Society, 185:511–

542. https://doi.org/10.1093/zoolinnean/zly053

Viglino, M., M. R. Buono, C. S. Gutstein, M. A. Cozzuol, and J. I. Cuitiño. 2018b. 

A New Dolphin from the Early Miocene of Patagonia, Argentina: Insights 

into the Evolution of Platanistoidea in the Southern Hemisphere. Acta Palaeontologica Polonica, 63:261–277. https://doi.org/10.4202/app.00441.2017

Weems, R. E., and L. E. Edwards. 2007. The Age and Provenance of “Eschrichtius” cephalus Cope (Mammalia: Cetacea). Journal of Vertebrate Paleontology, 27:752–756. https://doi.org/10.1671/0272-4634(2007)27[752:TAAPO

E]2.0.CO;2

Weems, R. E., L. E. Edwards, and B. Landacre. 2017. Geology and Biostratigraphy of the Potomac River Cliffs at Stratford Hall, Westmoreland County, 

Virginia. In From the Blue Ridge to the Beach: Geological Field Excursions 

across Virginia, ed. C. M. Bailey and S. Jaye, pp. 125–152. Geological Society 

of America Field Guide 47. Boulder, Colo.: Geological Society of America. 

https://doi.org/10.1130/2017.0047(05)

Whitmore, F. C. 1971. Vertebrate Biofacies and Paleoenvironments. In Environmental History of Maryland Miocene, ed. R. E. Gernant, T. G. Gibson, and F. 

C. Whitmore Jr., pp. 31–36. Guidebook 3. Baltimore: Maryland Geological 

Survey.

Whitmore, F. C. 1984. Cetaceans from the Calvert and Eastover Formations. In 

Stratigraphy and Paleontology of the Outcropping Tertiary Beds in the Pamunkey River Region, Central Virginia Coastal Plain, ed. L. W. Ward and 

K. Kraft, pp. 227–231. Norfolk, Va.: Atlantic Coastal Plain Geological Association.

Whitmore, F. C. 1994. Neogene Climate Change and the Emergence of the Modern Whale Fauna of the North Atlantic Ocean. In Contributions in Marine 

Mammal Paleontology Honoring Frank C. Whitmore, Jr., ed. A. Berta and 

T. A. Deméré. Proceedings of the San Diego Society of Natural History, 

29:223–227.

Whitmore, F. C., and J. A. Kaltenbach. 2008. Neogene Cetacea of the Lee Creek 

Phosphate Mine, North Carolina. Virginia Museum of Natural History Special Publication, 14:181–269.

Wilson, L. E. 1935. Miocene Marine Mammals from the Bakersfield Region, California. Bulletin of the Peabody Museum of Natural History, 4:1–143.

Woodward, B. L., and J. P. Winn. 2006. Apparent Lateralized Behavior in Gray 

Whales Feeding off the Central British Columbia Coast. Marine Mammal 

Science, 22:64–73. https://doi.org/10.1111/j.1748-7692.2006.00006.x

Zimmt, J. B., S. M. Kidwell, R. Lockwood, and M. Thirlwall. 2022. Strontium 

Isotope Stratigraphy Reveals 100 ky-Scale Condensation, Beveling, and Lateral Shingling of Transgressive Shell Beds in the Maryland Miocene. Palaios, 

37:553–573.
NUMBER 107 • 187

Index

Acrophyseter spp., 66

Alachua Formation, 44

Albicetus oxymycterus, 66, 68

alisphenoid, of Cammackacetus hazenorum gen. et sp. nov., 147. See also specific species

Allodelphinidae, 52. See also specific species

ammonium chloride, 52

Apalone

A. ferox, 3, 11–12, 11f, 44, 45f

A. lima, 3, 6, 12–13, 13f, 45f

A. mutica, 11

A. spinifera, 11–12, 11f

Aporotus recurvitostris, 171

Aquitanian-Serravallian Hawthorn Group, 44

Araeodelphis, 78

A. natator, 49, 77–82, 77f, 79–81f, 86, 96, 174

“Argyrocetus” joaquinensis, 158, 161

Atocetus spp., 126

Aulophyseter, 66

A. mediatlanticus, 49, 56, 62, 66–67f, 66–68, 174

A. morricei, 66

Auroracetus bakerae, 157

Bairdemys

B. hartsteini, 7

B. healeyorum, 6f

B. miocenica, 3, 6, 6f, 7–9, 8f, 44, 45f

basioccipital

of Cammackacetus hazenorum gen. et sp. nov., 147

of Caolodelphis milleri gen. et sp. nov., 161

of Enigmatocetus posidoni gen. et sp. nov., 165

of Grimadelphis spectorum gen. et sp. nov., 87

of Pomatodelphis santamaria sp. nov., 97

of Westmorelandelphis tacheroni gen. et sp. nov., 156

See also specific species

beaked whales, 50. See also specific species

Belonodelphis peruanus, 136

Brachydelphis mazeasi, 158

Brevirostrodelphis dividum
188 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

characteristics of, 138, 139

comparison to, 118, 136, 137, 138, 139, 

140, 151, 152, 155, 156

endemism of, 174

as Miocene delphinidan, 49

overview of, 107–108, 108–109f

Brevirostrodelphis gen. nov., 107–108

Brujadelphis ankylorostris, 158

Brygmophyseter shigensis, 66

Calvert Cliffs

map of, 5f

odontocetes of, faunal comparison of, 174, 

176t, 177

sediments of, 6

turtle discoveries in, 1, 3, 4, 46

See also specific locations

Calvert Formation

discoveries in, 4

location of, 72, 73

nonmarine turtle discoveries in, 6, 46

partial lower jaw from, 167–169, 167f, 

169f

Pungo River Formation and, 8–9, 12

stratigraphy in, 7f, 51

toothed whales found in, 50

See also specific discoveries

Cammack, David S., 142

Cammackacetus gen. nov., 142

Cammackacetus hazenorum gen. et sp. nov., 

49, 141, 142–144f, 142–147, 145t, 174

Caolodelphis gen. nov., 158

Caolodelphis milleri gen. et sp. nov., 49–50, 

158–161, 159–160f, 174

Caretta caretta, 22

caudal vertebrae

of Hadrodelphis calvertense, 117

of Herbeinodelphis nancei gen. et sp. nov., 

140–141

See also specific species

Caviziphius altirostris, 71

Central American Seaway, 71

cervical vertebrae

of Hadrodelphis calvertense, 115–116

of Herbeinodelphis nancei gen. et sp. nov., 

138–140

See also specific species

Chelone sp., 4

Chelonia

C. girundica, 22, 25f

C. grandaeva, 4

C. marylandica, 4, 16, 17f

C. mydas, 22, 25f

Cheloniidae, 14–18. See also specific species

Cheloniidae gen. et sp. indet, 22–25, 45f

cheloniid genera, 45

cheloniid taxa, 44

Chelydra, 46

Chesapeake Group, 50, 52, 178–179t

chicken turtles, 3

Chilcacetus cavirhinus, 158, 161

Chilcacetus-grade odontocete, 49

Choptank Formation, 7f, 46, 51, 73. See also

specific discoveries

Chrysemys, 34

C. isoni, 3, 6, 34–35, 34f, 36f, 44, 45f, 46

C. picta, 35

Clemmys, 44, 46

cooters, 3

Coronodon havensteini, 61

cribriform plate

of Herbeinodelphis nancei sp. nov., 138

of Pomatodelphis santamaria sp. nov., 96

See also specific species

Deirochelyinae, 30

Deirochelys

D. carri, 3, 6, 30–33, 44, 45f, 46

Deirochelys sp., 33f

D. reticulata, 30f

Delphinapterus leucas (beluga whale), 150

Delphinida, 52, 105–156, 176t. See also

specific species

Delphinodon

D. dividum, 108

D. mento, 108

Delphinus calvertensis, 50

dermatemydid turtle, 16

Dermochelyidae, 26–30. See also specific 

species

Dermochelys, 30

D. coriacea, 26f, 30

Diaphorocetus genus, 66

Eastover Formation, 6, 7f, 45. See also specific discoveries

Eboroziphius coelops, 71

Echovenator sandersi, 166

Emydidae, 30–33. See also specific species

Enigmatocetus gen. nov., 161

Enigmatocetus posidoni gen. et sp. nov., 50, 

161–167, 162–164f, 174

Eoplatanista spp., 158

Eosqualodon langewieschei, 60, 61

Eurhinodelphinidae, 49, 50, 98–101, 105, 

176t. See also specific species

exoccipital

of Cammackacetus hazenorum gen. et sp. 

nov., 147

of Caolodelphis milleri gen. et sp. nov., 

161

of Grimadelphis spectorum gen. et sp. 

nov., 87

of Westmorelandelphis tacheroni gen. et 

sp. nov., 156

See also specific species

Fairhaven Member, stratigraphic units at, 7. 

See also specific discoveries

faunal comparison, for Calvert Cliffs’ odontocetes, 174, 177

Floridemys, 40

F. hurdi, 3, 6, 42–43, 43f, 44, 45f, 46

F. nana, 40f, 42, 42–43f

F. nancei sp. nov., 3, 6, 43f, 44, 46

fossils, whitening of, 52

frontal

of Cammackacetus hazenorum gen. et sp. 

nov., 146

of Caolodelphis milleri gen. et sp. nov., 

160–161

of Enigmatocetus posidoni gen. et sp. nov., 

163

of Grimadelphis spectorum gen. et sp. 

nov., 86

of Herbeinodelphis nancei gen. et sp. nov., 

136

of Pictodelphis kidwellae gen. et sp. nov., 

151

of Pithanodelphis cornutus, 126

of Pomatodelphis santamaria sp. nov., 

96–97

of Squalodon murdochi sp. nov, 61–62

of Westmorelandelphis tacheroni gen. et 

sp. nov., 155

See also specific species

Furcacetus flexirostrum, 73, 77

Gascon, Mary Theresa (Fox), 93

Goniodelphis hudsoni, 168

Gopherus polyphemus, 42

Graptemys, 34, 46

G. geographica, 34, 34f

Graptemys sp., 3, 6, 33f, 34, 44, 45f

Grimadelphis gen. nov., 82

Grimadelphis spectorum gen. et sp. nov., 49, 

77, 82–87, 83–85f, 174

Grimsley, Gary, 82, 167, 168

Grimsley, Kyle, 82, 158

Hadrodelphis calvertense

comparison to, 138, 141, 142, 145, 146, 

147, 151, 168

endemism of, 174

as Miocene delphinidan, 49

overview of, 108, 110–114f, 115–116t, 

115–117, 121

sister grouping with, 147

Hawthorn Group, 44

Hazen, Robert and Margaret “Margee,” 142

Herbeinodelphis gen. nov., 128

Herbeinodelphis nancei gen. et sp. nov., 49, 

115, 128–141, 129–135f, 137t, 139–140t, 

174

Hesperotestudo, 39

H. bermudae, 42

H. crassiscutata, 39f

H. ducateli, 3, 6, 39–40, 41f, 44, 45f

H. percrassa, 39f

H. williamsi, 3, 6, 40, 41f, 44, 45–46, 45f

Horsehead Cliffs, Virginia, 4, 5f

Huaridelphis raimondii, 73, 77, 166

Inia geoffrensis, 117, 118, 157, 174
NUMBER 107 • 189

Inioidea, 52, 156–158. See also specific species

International Code of Zoological Nomenclature, 50

jugal

of Herbeinodelphis nancei gen. et sp. nov., 

137

of Westmorelandelphis tacheroni gen. et 

sp. nov., 156

See also specific species

Kampholophos serrulus, 118, 121, 145, 146

Kentriodon, 52

K. hoepfneri, 141, 155

K. pernix, 49, 105–107, 105–107f, 108, 

118, 136, 138, 140, 141, 151, 152, 155, 

168, 174, 177

K. schneideri, 151, 152, 156

Kentriodontidae, 49, 50, 52, 105, 117. See 

also specific species

Kidwell, Susan M., 147

Kinosternidae, 9. See also specific species

Kinosternidae indet (Kinosternon sp.), 3, 6, 

9–11, 10f, 45f

Kinosternon pannekollops, 9f

Kurobechelys tricarinata, 4

lacrimal

of Herbeinodelphis nancei gen. et sp. nov., 

137

of Pithanodelphis cornutus, 126

See also specific species

La Plata dolphin, 50

leatherback turtles, 3, 4. See also specific 

species

Lee Creek Mine, North Carolina, 8, 12. See 

also specific discoveries

Lepidochelys, 26, 44, 45

Lepidochelys sp., 3, 26f, 44, 45f

L. kempii, 26, 26f, 27f

L. olivacea, 22, 25f, 26

Leptodelphis stavropolitanus, 126

Liolithax kernensis, 118, 121

Little Cove Point Member, 26. See also specific discoveries

Livyatan melvillei, 66

Lophocetinae, 105, 117, 176t

Lophocetus, 50

L. calvertensis, 49, 118, 126–128, 

127–128f, 142, 145, 146, 174

L. pappus, 118, 171

Macrodelphinus kelloggi, 158

Macrokentriodon morani

characteristics of, 145, 146

comparison to, 137, 138, 141, 142, 146, 

151

endemism of, 174

as Miocene delphinidans, 49

overview of, 118, 118–120f, 121

as sister grouping, 117

Macrosqualodelphis ukupachai, 73, 77

Malaclemys, 46

malleus and incus, of Enigmatocetus 

posidoni gen. et sp. nov., 166. See also

specific species

mandible

of Herbeinodelphis nancei gen. et sp. nov., 

138

of Squalodon murdochi sp. nov, 62

of Westmorelandelphis tacheroni gen. et 

sp. nov., 156

See also specific species

map turtles, 3. See also specific species

marine turtles, 4. See also specific species

maxilla

of Cammackacetus hazenorum gen. et sp. 

nov., 145–146

of Caolodelphis milleri gen. et sp. nov., 

160

of Grimadelphis spectorum gen. et sp. 

nov., 86

of Herbeinodelphis nancei gen. et sp. nov., 

136

of Pictodelphis kidwellae gen. et sp. nov., 

150–151

of Pithanodelphis cornutus, 124

of Pomatodelphis santamaria sp. nov., 97

of Squalodon murdochi sp. nov., 61

of Westmorelandelphis tacheroni gen. et 

sp. nov., 152, 155

See also specific species

Medocinia, 77

Meherrinia isoni, 157

Mesoplodon, 69

Messapicetus, 69–71

Messapicetus sp., 49, 69–71, 70f

M. longirostris, 69–71

Miller, Thomas V. “Mike,” Jr., 158, 177

Miminiacetus gen. nov., 118

Miminiacetus pappus

comparison to, 141, 142, 145, 146, 151

endemism of, 174

as Miocene delphinidans, 49

overview of, 118, 118f, 121, 122–123f, 

151

Miocene cetaceans, 50

Miocene marine strata

discoveries of, 3

introduction to, 4–6

taxonomic history of, 4–6

Monodon monoceros, 166

Murdoch, Hillary, 128

Murdoch, Paul R., Jr., 56

musk turtles, 3. See also specific species

Nance, John R., 44, 128

nasal

of Cammackacetus hazenorum gen. et sp. 

nov., 146

of Grimadelphis spectorum gen. et sp. 

nov., 86

of Pictodelphis kidwellae gen. et sp. nov., 

151

of Pithanodelphis cornutus, 124

of Pomatodelphis santamaria sp. nov., 96

of Squalodon murdochi sp. nov, 61

of Westmorelandelphis tacheroni gen. et 

sp. nov., 155

See also specific species

Ninoziphius platyrostris, 71

nomina dubia, 171–174

Nomini Cliffs, Virginia, 5f. See also specific 

discoveries

nonmarine turtles, 3, 6. See also specific 

species

Notocetus vanbenedeni, 73, 77

occipital, of Herbeinodelphis nancei gen. et 

sp. nov., 137. See also specific species

odontocetes, 50

Odontoceti incertae sedis, 49, 158–171

Orycterocetus, 66

O. crocodilinus, 49, 56, 62, 63–65f, 

63–66, 174

O. quadratidens, 63

painted turtles, 3. See also specific species

palatine

of Cammackacetus hazenorum gen. et sp. 

nov., 146

of Herbeinodelphis nancei gen. et sp. nov., 

137

of Westmorelandelphis tacheroni gen. et 

sp. nov., 156

See also specific species

Pamunkey River, 4, 6, 46. See also specific 

discoveries

parietal and interparietal, of Cammackacetus 

hazenorum gen. et sp. nov., 147. See also

specific species

Pathological rostra, 171, 171–172f

Patuxent River, 4, 5f. See also specific discoveries

Pelodelphis gracilis, 171, 173f

Pelycorhamphus pertortus, 71

periotic

of Enigmatocetus posidoni gen. et sp. nov., 

165

of Herbeinodelphis nancei gen. et sp. nov., 

137–138

of Pomatodelphis santamaria sp. nov., 97

See also specific species

Peritresius virginianus, 4, 16

Philadelphia Academy of Natural Sciences, 4

Phoberodon arctirostris, 60, 61

Phocageneus venustus, 49, 72–73, 74–75f, 

77, 174

phylogenetic relationships, 52

Physeteridae, 49, 50, 63–68

Physeter macrocephalus, 66, 174
19 0 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY

Physeteroidea, 62–68, 176t

Physeteroidea indet., 68, 69f

Physterula dubusi, 66

Pictodelphis gen. nov., 147

Pictodelphis kidwellae gen. et sp. nov., 49, 

136, 138, 141, 147–151, 148–149f, 150t, 

174

Pithanodelphininae, 105, 126

Pithanodelphis cornutus, 49, 121, 124–126, 

125f, 155, 174

Platanista, 52, 166

P. gangetica, 77, 78, 86, 97, 166, 168

P. minor, 77

Platanistidae, 49, 50, 52, 77–87, 176t. See 

also specific species

Platanistidae indet., 82

Platanistoidea, 52, 56, 58

Pliocene marine strata

discoveries of, 3

introduction to, 4–6

taxonomic history of, 4–6

Plum Point Member, 7f. See also specific 

discoveries

Pollack Farm, Delaware, 9. See also specific 

discoveries

Pomatodelphininae, 87–98. See also specific 

species

Pomatodelphininae indet., 174, 176t

Pomatodelphis, 87, 88

P. bobengi, 82, 88, 93

P. inaequalis, 49, 77, 82, 88, 91–92f, 93, 

97, 98, 174

P. santamaria sp. nov., 49, 77, 82, 86, 88, 

93–98, 94–96f, 96, 174

P. stenorhynchus, 88

Pontoplanodes argentinus, 168

Pontoporia blainvillei, 156, 157

Pontoporiidae, 49, 50, 52, 156–158. See also

specific species

Popes Creek, Maryland, 4, 5f, 46. See also

specific discoveries

premaxilla

of Cammackacetus hazenorum gen. et sp. 

nov., 142, 145

of Caolodelphis milleri gen. et sp. nov., 

158, 160

of Grimadelphis spectorum gen. et sp. 

nov., 86

of Herbeinodelphis nancei gen. et sp. nov., 

136

of Pictodelphis kidwellae gen. et sp. nov., 

150

of Pithanodelphis cornutus, 124

of Pomatodelphis santamaria sp. nov., 93, 

96

of Squalodon murdochi sp. nov., 60–61

of Westmorelandelphis tacheroni gen. et 

sp. nov., 152

See also specific species

Prepomatodelphis, 82, 87

presphenoid

of Cammackacetus hazenorum gen. et sp. 

nov., 146

of Pomatodelphis santamaria sp. nov., 96

of Squalodon murdochi sp. nov, 62

See also specific species

Priscodelphinus crassangulum, 69

Procolpochelys

P. charlestonesis, 22

P. grandaeva, 3, 4, 18–22, 19f, 21f, 

23–24f, 26, 44, 45f

P. melii, 22, 23f

Procolpochelys sp., 18f

Psephophorus, 44

P. calvertensis, 4, 28, 29f

P. polygonus, 3, 22, 26–30, 29f, 31–32f, 

44, 45f

Pseudemys, 37

P. caelata, 3, 6, 33f, 38, 44, 45f, 46

P. williamsi, 3, 6, 33f, 37–38f, 38, 44, 45f

pterygoid

of Cammackacetus hazenorum gen. et sp. 

nov., 146

of Westmorelandelphis tacheroni gen. et 

sp. nov., 156

See also specific species

Pungo River Formation, 8, 12. See also specific discoveries

Rhabdosteus genus, 104

Rhea, David, 147

ribs

of Hadrodelphis calvertense, 117

of Herbeinodelphis nancei gen. et sp. nov., 

141

See also specific species

rostrum, from St. Marys Formation, 

169–171, 170f

Rudicetus squalodontoides, 136, 137, 141, 

151, 152, 155, 156

Scaldicetus caretti, 68

Schizodelphis, 101–105

S. barnesi, 49, 101, 104–105, 104f, 174

S. crassangulum, 69

S. morckhoviensis, 49, 98, 101, 103f, 174

S. sulcatus, 101

sea turtles, 3, 4, 46. See also specific species

Semirostrum ceruttii, 168

shark-toothed whales (Squalodontidae), 53. 

See also specific species

Shattuck-Zones, 4, 6, 7f, 52. See also specific 

discoveries

Siddons, Derek, 161

side-necked turtles, 3, 6. See also specific 

species

Simocetus rayi, 166

slider turtles, 3. See also specific species

softshell turtles, 3, 6. See also specific species

Sophianaecetus commenticius, 124, 126

South Asian river dolphins, 50, 77, 

sperm whales, 50. See also specific species

Squalodelphinidae, 49, 50, 52, 56, 72–77, 

176t. See also specific species

Squalodelphinidae indet., 73, 75–77, 76f

Squalodelphis fabianii, 73, 77

Squalodon, 53–62

S. antwerpiensis, 60

S. barbarus, 60

S. bariensis, 60

S. bellunensis, 60, 61

S. calvertensis, 49, 53–55f, 53–56, 60, 61, 

62, 174, 177t, 177

S. grateloupii, 53

S. murdochi sp. nov., 49, 56–62, 58–59f, 

174

S. peregrinus, 60

Squalodon sp. nov., 60

S. whitmorei, 30, 49, 53, 56, 56–57f, 60, 

61, 174

Squalodontidae, 49, 50, 52, 53. See also

specific species

Squaloziphius emlongi, 163, 166

squamosal

of Caolodelphis milleri gen. et sp. nov., 161

of Enigmatocetus posidoni gen. et sp. nov., 

163, 165

of Grimadelphis spectorum gen. et sp. 

nov., 86

of Herbeinodelphis nancei gen. et sp. nov., 

137

of Pithanodelphis cornutus, 126

of Pomatodelphis santamaria sp. nov., 97

of Squalodon murdochi sp. nov, 62

of Westmorelandelphis tacheroni gen. et 

sp. nov., 155–156

See also specific species

Stenasodelphis russellae, 49, 156–157f, 

156–158, 171, 174

St. Marys Formation

nonmarine turtle discoveries in, 46

rostrum from, 169–171, 170f

sea turtle discoveries in, 6, 46

stratigraphy in, 7f, 51

See also specific discoveries

Stratford Cliffs, Virginia, 5f. See also specific 

discoveries

stratigraphic distribution, 7f, 45, 177, 

178–179t

Stylemys lineage, 42

supraoccipital

of Cammackacetus hazenorum gen. et sp. 

nov., 146–147

of Caolodelphis milleri gen. et sp. nov., 

161

of Grimadelphis spectorum gen. et sp. 

nov., 87

of Pithanodelphis cornutus, 126

of Pomatodelphis santamaria sp. nov., 97

of Squalodon murdochi sp. nov, 62

of Westmorelandelphis tacheroni gen. et 

sp. nov., 155

See also specific species

Syllomus

S. aegyptiacus, 4, 16

S. crispatus, 4, 16

systematic paleontology, 6f
NUMBER 107 • 191

Tacheron, Ben, 152

Tagicetus joneti, 117, 126, 136, 151, 152

Taphrosphys miocenica, 6

Terrapene, 44

Testudinidae, 39, 42. See also specific species

Testudo ducateli, 6

Thecachampsa antiquus, 30

Thomas Residence, Maryland, 5f

thoracic vertebrae

of Enigmatocetus posidoni gen. et sp. nov., 

166

of Hadrodelphis calvertense, 116–117

of Herbeinodelphis nancei gen. et sp. nov., 

140

See also specific species

toothed whale

geological context regarding, 52

history of research regarding, 50–52

locations of, 49, 50

material and methods regarding, 52–53

phylogenetic relationships and, 52

statistics regarding, 49, 50

systematic and taxonomy regarding, 52

See also specific species

tortoises, 3, 6

Trachemys, 35

T. inflata, 3, 33f, 35–37, 35f, 44, 45f

Trachemys sp., 6

T. scripta, 35f, 37

Trachyaspis

T. aegyptiaca, 4

T. lardyi, 3, 4, 14–18, 14f, 17f, 22, 44, 45f

Tretosphys gabbii, 171–174, 175f

“Tribus Carettini,” 22

Trionychidae, 11–12. See also specific species

Trionyx, 12

T. cellulosus, 4

T. lima, 4, 6

T. triungius, 12

Tusciziphius crispus, 71, 72

tympanic bulla

of Enigmatocetus posidoni gen. et sp. nov., 

165–166

of Herbeinodelphis nancei gen. et sp. nov., 

138

of Pomatodelphis santamaria sp. nov., 98

See also specific species

vertebral column, of Hadrodelphis calvertense, 115. See also specific species

vomer

of Cammackacetus hazenorum gen. et sp. 

nov., 146

of Caolodelphis milleri gen. et sp. nov., 

161

of Grimadelphis spectorum gen. et sp. 

nov., 86–87

of Herbeinodelphis nancei gen. et sp. nov., 

136

See also specific species

Westmoreland County, Virginia, 4, 5f, 18. 

See also specific discoveries

Westmorelandelphis gen. nov., 152

Westmorelandelphis tacheroni gen. et sp. 

nov., 49, 136, 138, 141, 151, 152–156, 

153–154f, 155t, 174

whitening, of fossils, 52

Xerobatinae, 39

Xiphiacetus, 98–101

X. bossi, 49, 98, 99–100, 99f, 174

X. cristatus, 49, 98, 99, 101, 102f, 174

Xiphias gladius, 98

Yaquinacetus meadi, 166

Yorktown Formation, 18. See also specific 

discoveries

Zarhachis, 166

Z. flagellator, 49, 77, 78, 82, 86, 87–88, 

87f, 89–90f, 93, 96, 97, 174, 177

Ziphiidae, 49, 50, 68–72. See also specific 

species

Ziphiidae incertae sedis, 49

Ziphiidae indet., 70f, 71–72

Zygophyseter varolai, 66
192 • SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY