ARTICLE

Memoir of the Fukui Prefectural Dinosaur Museum 16: 29–38 (2017)© by the Fukui Prefectural Dinosaur Museum

FIRST OCCURRENCE OF A TYRANNOSAUROID DINOSAUR FROM THE LOWERCAMPANIAN MERCHANTVILLE FORMATION OF DELAWARE, USA
Sebastian G. DALMAN1, Steven E. JASINSKI2,3 and Spencer G. LUCAS1New Mexico Museum of Natural History and Science, 1801 Mountain Road N. W. Albuquerque, NM 87104 USA
The State Museum of Pennsylvania, Section of Paleontology and Geology, 300 North Street, Harrisburg, PA 17120-0024 USA
3
University of Pennsylvania, Department of Earth and Environmental Science, Philadelphia, PA 19104-6316 USA
1

2

ABSTRACTThis study provides a detailed osteological description of an isolated proximal caudal centrum and two nearlycomplete isolated metatarsals II and IV of the left foot of a gracile theropod dinosaur from the Lower Campanianof the Merchantville Formation in northern Delaware, USA. The caudal centrum and the metatarsals are referred to
Tyrannosauroidea. The centrum is not well preserved, and thus not diagnostic; however, both metatarsals are diagnostic.
The referral to Tyrannosauroidea is supported by several morphological features, including extensive surfaces on
metatarsals II and IV for the articulation with metatarsal III, and a characteristic low, slightly convex muscle scaron metatarsal IV developed as a thin low ridge located on the posterior surface between the M. gastrocnemius parslateralis insertion scar and the metatarsal III articular surface. This ridge has been previously interpreted as the plantar
ridge, which is present in some derived Late Campanian tyrannosauroid taxa. Additionally, metatarsal IV has a deep
medial notch for the accommodation of an“L”– shaped proximal articulation of metatarsal III, and a“U”– shaped
proximal articular end. The Merchantville Formation tyrannosauroid exhibits arctometatarsalian metatarsals, as dotyrannosaurids. The Merchantville Formation tyrannosauroid is differentiated from other known basal and derived
tyrannosaurids by having a characteristically shaped proximal articular surface of metatarsal II in which the proximal
and posterior ends lie on the long axis of the proximal articular surface. However, the posterior proximal articularsurface of metatarsal II is not as strongly angled laterally as in more derived tyrannosauroids. The Merchantville
Formation tyrannosauroid adds to the record of Appalachian tyrannosauroid, evolution and paleostratigraphic position,and provides new morphological information about the metatarsal anatomy of these iconic theropods.
Key words : Tyrannosauroidea, Theropoda, Upper Cretaceous, early Campanian, Delaware, United States

INTRODUCTION

the world, being distributed from modern day Alaska to modern
day Mexico (e.g., Russell, 1970; Carr and Williamson, 2010;
Carr et al., 2011; Lehman and Wick, 2012; Loewen et al., 2013;
Fiorillo and Tykoski, 2014; Peecook et al., 2014; Dalman andLucas, 2015, 2016; Serrano-Brañas et al., 2017). The Laramidian
tyrannosauroids comprise both basal and derived forms, with thederived forms divisible into two subfamilies: Albertosaurinae
and Tyrannosaurinae (Currie, 2003, 2005). The Appalachiantyrannosauroids, on the other hand, comprise basal forms, andmost fall outside of these clades (e.g., Carr et al., 2005; Brusatte
et al., 2011; Brusatte and Carr, 2016).
The best known and most complete Appalachian tyrannosauroid
taxa are Appalachiosaurus montgomeriensis (Carr et al., 2005)
and Dryptosaurus aquilunguis (Marsh, 1877). Appalachiosaurus
is the more completely known taxon, and is from the Middle
Campanian of Alabama, USA, whereas Dryptosaurus is basedon several isolated cranial and postcranial skeletal elements fromThe skeletal fossil remains of eastern North American(Appalachian) tyrannosauroid dinosaurs are rare (Schwimmer
et al., 1993; Schwimmer, 1989, 2004; Carr et al., 2005). They
are found in the Cenomanian–Turonian and Campanian–
Maastrichtian deposits throughout this part of the continent,suggesting a long stratigraphic range and wide paleobiogeographic
distribution of these iconic theropods (e.g., Schwimmer, 1989,
2004; Schwimmer et al., 1993; Carr et al., 2005; Brusatte et al.,2011; Dalman et al., 2016). In contrast, the Upper Cretaceous
terrestrial deposits of Laramidia preserve one of the richest, mostdiverse assemblages of tyrannosauroid fossils found anywhere in
Received April 30, 2017. Accepted September 28, 2017.
Corresponding author ― Sebastian G. DALMAN
E-mail: sebastiandalman＊yahoo.com
29

30

SEBASTIAN G. DALMAN, STEVEN E. JASINSKI AND SPENCER G. LUCAS

the Upper Maastrichtian of New Jersey, USA. The osteologicaldescriptions by Carpenter et al. (1997) and the phylogenetic
analyses by Carr et al. (2005), Brusatte et al. (2010, 2011), and,most recently, by Brusatte and Carr (2016), place these taxa
within the Tyrannosauroidea. However, in the paleobiogeographic
analysis of Brusatte and Carr (2016), Dryptosaurus has
been recovered as a more derived tyrannosauroid. Althoughfragmentary, the Appalachian tyrannosauroids provide important
information about the evolution, taxonomic diversity, andpaleogeographic distribution of these theropods throughout North
America during most of the Cretaceous.
The discovery in 1975 by Ralph Johnson and Ray Meyer(Monmouth Amateur Paleontologists Society in Long Branch,
New Jersey) of an isolated proximal caudal centrum andtwo nearly complete left metatarsals II and IV in the lower
Campanian Merchantville Formation (Upper Cretaceous)along the Chesapeake and Delaware Canal in northern
Delaware has remained the subject of unresolved taxonomic
relationships. Previously, Horner (1979) referred the specimens
to Ornithomimidae indeterminate without a formal description.
However, based on their overall morphology, the specimens arehere referred to Tyrannosauroidea, and thus represent one ofthe oldest occurrences of Appalachian tyrannosauroids. These
specimens predate Appalachiosaurus and Dryptosaurus andsome of the Laramidian tyrannosauroids such as Albertosaurus,
Daspletosaurus, Gorgosaurus, Lythronax, Nanotyrannus,
Nanuqsaurus, and Tyrannosaurus. The identification oftyrannosauroids in a stratigraphically older unit provides further
support for a relatively wide paleobiogeographic distribution ofthese theropods during the Late Cretaceous in North America.
Institutional abbreviations
AMNH, American Museum of Natural History, New York, New
York, USA; FMNH, Field Museum of Natural History, Chicago,
Illinois, USA; IGM, Colección Nacional de Paleontología,
Instituto de Geología, Universidad Nacional Autónoma deMéxico, Mexico City, México; MIWG, Museum of Isle of Wight

Geology, Isle of Wight, England, UK; NMC, Canadian Museumof Nature, Ottawa, Ontario, Canada; NMMNH, New Mexico
Museum of Natural History and Science, Albuquerque, New
Mexico, USA; PIN, Palaeontological Institute, Moscow, Russia;
RMM, Red Mountain Museum, Birmingham, Alabama, USA;
TMP, Royal Tyrrell Museum of Palaeontology, Drumheller,
Alberta, Canada; TMM, Texas Memorial Museum, Austin, Texas,
USA; UMNH, Natural History Museum of Utah, Salt Lake City,
Utah, USA; YPM, Yale Peabody Museum of Natural History,
New Haven, Connecticut (formerly at PU, Division of Vertebrate
Paleontology Princeton University, Princeton, New Jersey), USA;
ZPAL, Institute of Palaeobiology of the Polish Academy of
Sciences, Warsaw, Poland.
Geologic Setting
The isolated caudal centrum and two metatarsals describedhere were found at the locality along the north bank of the
Chesapeake and Delaware Canal, ~ 1.2 km east of Summit Bridge
Route 301 and 0.8 km north of Summit Delaware (Fig. 1). In
the bank of the Chesapeake and Delaware Canal the following
section is exposed, in ascending order (Owens et al., 1970):(1) Merchantville Formation; (2) Englishtown Formation; (3)Marshalltown Formation; and (4) Mount Laurel Formation. These
geologic formations originated from sediments eroded from theAppalachian Mountains to the west.
The Merchantville Formation is located in northern Delawareand represents a mixture of terrestrial and lagoonal environments(Baird and Galton, 1981). The sediments of the formation arelight to dark-gray, very micaceous, glauconitic, very silty, fineto very ﬁne-grained sand and silt, and were deposited during the
Early Campanian, ~ 83.5 Ma (Petters, 1976; Ramsey, 2005). The
thickness of the formation is usually ~ 7 m, but ranges up to ~ 36
m in some places (Owens et al., 1970; Lauginiger, 1988; Ramsey,2005).
The base of the Merchantville Formation is glauconitic sandthat is covered by the silt of the main part of Merchantville
Formation, which in turn, grades into the quartz sands of the

FIGURE 1. Map of the north bank of the Chesapeake and Delaware Canal, Delaware. A, Locality of the Merchantville Formation tyrannosauroid , ~ 1.2 km
east of Summit Bridge, Route 301 and 0.8 km north of Summit Delaware (modiﬁed from Baird and Galton, 1981).

FIRST RECORD OF TYRANNOSAUROID FROM DELAWARE, USA

Englishtown Formation (Curran, 1985). The sands that containglauconite were deposited in deep water, whereas the quartz silts
and sands indicate shallow water. Curran (1985) interpreted theEnglishtown Formation as deposits in the upper shore face lower
foreshore zone. Exposures of the Englishtown Formation aremarked by an unconformity that separates it from the overlying
Marshalltown Formation.
The Merchantville Formation yields a fragmentary but
significant Upper Cretaceous vertebrate fauna composed ofchondrichthyans, osteichthyans, crocodylians, dinosaurs, marine
reptiles such as mosasaurs, pterosaurs, and turtles (e.g., Bairdand Galton, 1981; Lauginiger, 1988; Gallagher, 1993, 2005). The
dinosaurian fauna includes hadrosaurids and medium-sized, nonavian theropods (e.g., Baird and Horner, 1977; Horner, 1979;
Lauginiger, 1988; Gallagher, 2004; Weishampel et al., 2004;
Weishampel, 2004, 2006).
SYSTEMATICSYPM VPPU 021795, metatarsals II and IV of the left pes, andYPM VPPU 022416 caudal centrum, were originally considered
as belonging to the Ornithomimidae (Horner, 1979). However,in this study they are reassigned to Tyrannosauroidea based on
several key characters, including the“D”– shaped proximal
articular surface of metatarsal II, the lateral notch for thearticulation with the proximal end of metatarsal III, large articularsurfaces on the shaft for the articulation with metatarsal III, the“U”– shaped proximal articular surface of metatarsal IV and the
medial notch for the articulation with the“L”– shaped proximal
end of metatarsal III.
DINOSAURIA Owen, 1842
THEROPODA Marsh, 1881
COELUROSAURIA von Huene, 1914
TYRANNOSAUROIDEA Walker, 1964
Tyrannosauroidea indeterminate
Material.―YPM VPPU 021795, metatarsal II and IV of theleft pes, YPM VPPU 022416, caudal centrum.
Locality, horizon and age .―North bank of the Chesapeakeand Delaware Canal, Delaware, ~ 1.2 km east of Summit Bridge,
Route 301 and 0.8 km north of Summit Delaware. Merchantville
Formation, Late Cretaceous (Early Campanian) (Fig. 1).
DESCRIPTION
Vertebra.―YPM VPPU 022416 is identified as an anteriorcaudal centrum (Fig. 2). The centrum is not well-preserved andlacks important diagnostic features. It is crushed and heavily
eroded on one side, whereas the other side preserves the shapeand part of the original outer bone surface. The centrum is notdiagnostic due to its poor preservation; however, the overall
shape is consistent with that of a tyrannosauroid caudal centrum.
The centrum was found with the metatarsals described below,

31

suggesting that the centrum and both metatarsals may belong to
the same animal.
Metatarsals.―The left metatarsal II, YPM VPPU 021795,is missing only the distal condyle (Fig. 3). The length of thepreserved metatarsal is 30 cm (Table 1).
As in other tyrannosauroids (e.g., Brochu, 2003; Carr etal., 2005), the proximal end of the metatarsal II, YPM VPPU
021795 is“D”– shaped. The proximal articular surface is larger
than that of the metatarsal IV and is expanded mediolaterally
and anteroposteriorly beyond the metatarsal shaft. The articularsurface in proximal view is more expanded mediolaterally inthe anterior region (5 cm) than in the posterior region (3.5 cm).
The anteroposterior length of the proximal articular surface ofthe metatarsal II is 8 cm. The surface ventral to the proximal
articulation has a“swollen”appearance, except for the lateralsurface, which is ﬂat. The lateral surface of the proximal end hasa characteristic shallow and narrow lateral notch for articulation
with the proximal end of metatarsal III. The length of the notch
is 3 cm, and the width 1.5 cm. Anterior to this notch is a flat
articular surface, which is partially reconstructed, that is 4
cm long and 3 cm wide. This surface contacted the proximal
anteromedial surface of metatarsal IV, as in other tyrannosauroids(e.g., Brochu, 2003). Directly posterior to the lateral notch is a
ﬂat articular surface for metatarsal III that is 3 cm long and 3 cm
wide anteroposteriorly. Distal to this surface is an elongate rugose
surface that is oriented anterolaterally. This rugosity marks theinsertion site for M. tibialis anterior (Carrano and Hutchinson,
2002). Distal to the insertion site for M. gastrocnemius parslateralis is a larger articular surface with smooth and subtle texture
that occupies half the length of the lateral shaft of metatarsal II.
This characteristic surface is referred to as the articular scar for
metatarsal III and is present in all known tyrannosauroids (e.g.
Brochu 2003). Both articular surfaces are separated from eachother by a characteristic elongate ridge. The far larger articularsurface originates at the distal end of this ridge and extends farther
distally. The larger surface is narrow (approximately 3 cm), and at
the proximal extremity it begins to ﬂare anteroposteriorly towards
the distal end of the shaft.
The shaft of metatarsal II is relatively straight in anterior andposterior aspect, whereas in lateral and medial aspect the shaft
is slightly convex in a way that is characteristic of all known
tyrannosauroids (e.g., Carrano and Hutchinson, 2002; Brochu,
2003; Carr et al., 2005; Brusatte et al., 2010). The posterior
surface of the shaft is ﬂat, and the anterior surface is strongly
convex. The medial and lateral corners of the posterior surface ofthe shaft are slightly convex. Anteroposteriorly, the shaft is broadand closely resembles the condition of derived tyrannosaurids.
The posterior surface of the shaft has a posteromedially oriented,
rugose, teardrop-shaped concavity, which is interpreted as theinsertion site for M. gastrocnemius pars lateralis (e.g., Carranoand Hutchinson, 2002). Its position and overall morphology
closely resemble those of known tyrannosaurids (e.g., Carranoand Hutchinson, 2002; Brochu, 2003; Carr et al., 2005).
The posteromedial surface of the metatarsal shaft contains two
small rugosities (Fig. 4). The proximalmost rugosity is small.

32

SEBASTIAN G. DALMAN, STEVEN E. JASINSKI AND SPENCER G. LUCASFIGURE 2. Tyrannosauroid proximal caudal vertebra (YPM VPPU
022416). A, right lateral view; B, left lateral view; C, dorsal view; D,ventral view; E, anterior view; F, posterior view. Bar = 5 cm.

FIGURE 3. Tyrannosauroid left metatarsal II (YPM VPPU 021795).
A, anterior view; B, posterior view; C, medial view; D, lateral view; E,
proximal view. Abbreviations are in Appendix 1. Bar = 5 cm.

Directly distal to it is a much larger, teardrop-shaped rugositythat marks the surface attachment for metatarsal I (Brochu, 2003;
Carrano et al., 2005; Hattori, 2016). However, there are competinginterpretations of the scar on metatarsal II for the attachmentof metatarsal I (e.g., Tarsitano and Hecht, 1980; Carrano andHutchinson, 2002).
The left metatarsal IV, YPM VPPU 021795, is essentiallycomplete (Fig. 5; Table 2). The total length of the preserved
metatarsal is 38 cm, and its circumference is 9.5 cm at midshaft.
The minimum circumference is 9.1 cm and is present in two
regions of the shaft: distal to the proximal end and dorsal to the
distal condyles. The metatarsal shaft is straight in all aspects.
The distal portion of the shaft approximately 7.5 cm dorsal tothe distal condyles is broken. When associated, the distal end isangled slightly laterally, and the lateral condyle is shorter thanthe medial condyle. The medial surface of the metatarsal shaft is
ﬂat, which indicates that metatarsal IV was tightly appressed tometatarsal III for its entire length.
The proximal articular surface of metatarsal IV YPM VPPU
021795 is“U”– shaped, and, in the posterior region, has a wellmarked articulation for distal tarsal four (dt4) (e.g., Carrano andHutchinson, 2002; Brochu, 2003; Brusatte et al., 2011; Lehman
and Wick, 2012; Thomson et al., 2013; Peecook et al., 2014). The
convex surface of the“U”– shaped proximal articular end faces
laterally. A small semicircular rugosity located at the posterolateraledge of the proximal articulation marks the contact withmetatarsal V (e.g., Carrano and Hutchinson, 2002). The medialsurface of the proximal end of metatarsal IV has a characteristic
narrow, but deep (2 cm) concave notch, against which the“L”– shaped proximal end of metatarsal III articulates (e.g., Holtz,
1994; Brochu, 2003; Lehman and Wick, 2012; Thomson et al.,2013; Peecook et al., 2014). The notch continues distally on the
medial surface of the metatarsal IV for approximately 5 cm, but
as it approaches the shaft it slightly widens and gradually tapers

TABLE 1. Measurements of the metatarsal II (YPM VPPU 021795). Measurements in mm. *(estimatedlength) refers to the length of the complete metatarsal.

TABLE 2. Measurements of metatarsal IV (YPM VPPU 021795). Measurements in mm *(estimated length)refers to the length of the complete metatarsal.

FIRST RECORD OF TYRANNOSAUROID FROM DELAWARE, USA

FIGURE 4. Tyrannosauroid posterolateral surface of the shaft of the left
metatarsal II (YPM VPPU 021795) showing two small rugosities (M. ta
and mt-1). Abbreviations are in Appendix 1. Bars = 2 cm.

as it merges into the medial surface of the shaft. Posterior tothe medial notch is a“tear-drop”– shaped articular surface formetatarsal II, and anterior to the notch is the articular surface formetatarsal III (e.g., Brochu, 2003). Between the proximal notch
for metatarsal III and the tear-drop articular facet lies an ovoid
rugosity that is nearly twice as long as it is wide. This rugosity
marks the insertion site for the M. tibialis anterior (e.g., Carranoand Hutchinson, 2002).

33

The posterior surface of the shaft is ﬂat, and the anterior
surface is convex. Together they give the proximal half of the
shaft a subtriangular cross-section, with the sharpest corners
situated medially and laterally. At mid-length, the shaft begins tocurve and twists slightly laterally, and the curvature is visible atthe broken distal end.
The posterior surface of the shaft of metatarsal IV has a distinct
elongate rugosity, visible in lateral and medial aspects. The
rugosity originates slightly distal to the proximal articular surface
and extends for most of the shaft's length, although in the middleof the bone the rugosity curves gently laterally, and continues
down the shaft in this trajectory. This elongated rugosity isinterpreted as the insertion site for the M. gastrocnemius parslateralis (e.g., Carrano and Hutchinson, 2002).
Located on the medial surface of the metatarsal shaft justventral to the medial notch is an elongated,“tear-drop”– shaped
surface, interpreted as the insertion site for the M. tibialis anterior(e.g., Carrano and Hutchinson, 2002). Approximately 6 cm distal
to the proximal articular surface is another much larger articularsurface for metatarsal III. It originates on the posteromedialsurface of the metatarsal shaft and continues distally (e.g.,
Brochu, 2003; Peecook et al., 2014). However, near the midshaft

FIGURE 5. Tyrannosauroid left metatarsal IV (YPM VPPU 021795). A, anterior view; B, posterior view; C, lateral view; D, medial view; E, proximal;F, distal view. Abbreviations are in Appendix 1. Bar = 10 cm.

34

SEBASTIAN G. DALMAN, STEVEN E. JASINSKI AND SPENCER G. LUCAS

it begins to ﬂare anteroposteriorly and extends near the distal endof the bone in such a way that it occupies the entire width of the
shaft.
A characteristic low, distolaterally-trending ridge is situated on
the anterior surface of the shaft. The ridge originates anteroventral
to the insertion site for the M. tibialis anterior and extends distally
nearly half the length of the shaft. At its terminal end the ridge
gradually merges into the shaft, and the surface distal to it is ﬂatand smooth. The posterior surface between the M. gastrocnemiuspars lateralis insertion scar and the metatarsal III articular surface
is slightly convex, with a muscle scar developed as a thin, lowridge, which has been interpreted as the plantar ridge by Thomson
et al. (2013). The plantar ridge emerges from the articular surface
for metatarsal III, and is oriented distolaterally. It extends along
the posteromedial margin and continues distally for approximately
10 cm along the long axis of the distal portion of the shaft. It thenmerges with the dorsal surface of the lateral distal condyle.
The distal articular surface of the metatarsal IV is asymmetrical.
The medial condyle is mediolaterally wider and anteroposteriorly
longer than the lateral condyle. The lateral ligament pit is shallow,
whereas the medial ligament pit is deep. In contrast, the lateral
ligament fossa that surrounds the ligament pit is larger than the
medial ligament fossa. Both fossae are not deeply inserted aroundthe ligament pits. The anterior hyperextensor pit is a larger“U”– shaped depression situated proximal to the distal condyle. In
posterior view, the condyles are separated by a deep intercondylar
sulcus.
DISCUSSION
Horner (1979) previously referred the metatarsals II andIV (YPM VPPU 021795) to Ornithomimidae indeterminate.
However, the metatarsals exhibit typical tyrannosauroid
morphology. The suite of morphological characters that
support the referral of YPM VPPU 021795 to a tyrannosauroid
dinosaur include the“D”– shaped proximal articular surfaceof metatarsal II, the lateral notch for the articulation with theproximal end of metatarsal III, large articular surfaces on theshaft for the articulation with metatarsal III, the“U”– shaped
proximal articular surface of metatarsal IV and the medial notch
for the articulation with the“L”– shaped proximal end of themetatarsal III. On the basis of these characters, the proximal endof metatarsal III of YPM VPPU 021795 was pinched between
metatarsals II and IV in a way characteristic of arctometatarsalian
theropods (e.g., Holtz, 1994).
However, at the time when Horner referred the metatarsals
to an indeterminate ornithomimid theropod, the fossil record ofNorth American tyrannosauroids was less complete than it istoday, and the term Arctometatarsalia (Holtz, 1994) had not yet
been proposed. Theropods with arctometatarsalian feet include
most of the tyrannosauroids, but also include other coelurosaurianfamilies such as Alvarezsauridae, Avimimidae, Caenagnathidae,
Ornithomimidae, Oviraptoridae, and Troodontidae, which
all exhibit a pinched proximal end of metatarsal III between
metatarsals II and IV. As noted in the description, the posterior

surface of metatarsal IV of the Merchantville tyrannosauroid
is slightly convex and has a muscle scar developed as a thin,
low ridge situated between the M. gastrocnemius pars lateralis
insertion scar and the metatarsal III articular surface.
Although the metatarsals of the Merchantville Formation
tyrannosauroid exhibit the morphology of a derived
tyrannosauroid, they can be differentiated from other known
tyrannosauroids by the relatively straight proximal articularsurface of metatarsal II. In general, the medial margin of theproximal articular surface of metatarsal II in more derived
tyrannosauroids (e.g., Appalachiosaurus, Bistahieversor,
Gorgosaurus, Tarbosaurus, and Tyrannosaurus) (Fig. 6) isstrongly convex, and the posterior portion of the proximal
end is angled laterally. As a result, the lateral notch in derived
tyrannosauroids such as Appalachiosaurus, Bistahieversor,
Gorgosaurus, and Tyrannosaurus is more pronounced than it is in
the Merchantville Formation tyrannosauroid. The characteristic
morphology of the proximal articular surface of metatarsal II(YPM VPPU 021795) most likely represents a basal condition
shared with the Late Jurassic coelurid theropods that exhibit
similar morphologies, such as Coelurus fragilis, Ornitholestes
hermanni and Tanycolagreus topwilsoni (=Stokesosaurus
clevelandi) (see Carpenter et al., 2005a; ﬁg. 2.15, p. 44; Carpenter
et al., 2005b; fig. 3.13, p. 68), and some Late Cretaceous
ornithomimids such as Gallimimus bullatus (Osmólska et al.,1972) and Ornithomimus velox (Osborn, 1916) (Fig. 7). However,in Gallimimus (ZPAL Mg D-I /94) the posterior end of theproximal articular surface is more angled laterally than in the
Merchantville tyrannosauroid or in O. velox (YPM VP 0542).
In the past decade and in recent years, detailed osteological andcomparative anatomical studies of the lower appendicular skeletal

FIGURE 6. Tyrannosauroids left metatarsal II proximal view. A,
Appalachiosaurus montgomeriensis (RMM 6670); B, Bistahieversor
sealeyi (NMMNH P-25049); C, Gorgosaurus libratus (YPM VP 055672);
D, Tyrannosaurus rex (FMNH PR2081). Not to scale.

FIRST RECORD OF TYRANNOSAUROID FROM DELAWARE, USAelements of tyrannosauroid materials, particularly of new taxa,
have been written (e.g., Carrano and Hutchinson, 2002; Snively
and Russell, 2002; Brochu, 2003; Snively et al., 2004; Brusatte
et al., 2012; Lehman and Wick, 2012; Thomson et al., 2013;
Peecook et al., 2014; Hattori, 2016). These studies provide new
information about the anatomy of tyrannosauroid metatarsals,
which, among other known theropod families and otherarctometatarsalians, are unique. The most notable morphologicalfeature is the“L”– shaped proximal articular end of metatarsal
III, which is present in both basal and derived tyrannosauroids. In
other arctometatarsalian theropods (e.g., ornithomimosaurs) thelateral and medial surfaces of the proximal end of metatarsal III
are ﬂat and lack the“L”– shape morphology (Fig. 7).
At present it is not clear when and where the arctometatarsaliantyrannosauroids first evolved. However, based on fragmentarytyrannosauroid material from the Cenomanian of New Jersey,
the arctometatarsalian tyrannosauroids were already present inAppalachia during an early stage of the Late Cretaceous. The
recovery of fragmentary specimens and several diagnostic teeth
pertaining to tyrannosauroids from the pre- and early Campaniandeposits of Laramidia (e.g., Kirkland et al., 1997; Cifelli etal., 1997, 1999; Eaton et al., 1999; Parrish, 1999; Garrison etal., 2007; Larson, 2008; Zanno and Makovicky, 2011; Wick etal., 2015; Dalman and Lucas, 2016; Krumenacker et al., 2016)
suggests that these theropods were already present in North
America and had a wide paleobiogeographic and stratigraphic
occurrence. The earliest recorded occurrence of tyrannosauroids
in North America is from the Aptian/Albian deposits of the
Cloverly Formation in Wyoming (Zanno and Makovicky, 2011)
and the Wayan Formation of Idaho (Krumenacker et al., 2016).
For most of the Aptian/Albian, the eastern and western parts ofNorth America were not separated by the inland seaway (Blakey,2014), which allowed the dinosaurs, and, in particular thetyrannosauroids, to spread across the continent and inhabit various
paleobiogeographic/ paleoecological niches. By the middle
Coniacian (96 Ma), the inland seaway opened and remained
open for approximately 25 million years (Blakey, 2014). The
seaway started to close in the south during the late Campanian/early Maastrichtian, forming a land bridge where Colorado and
New Mexico are today (Blakey, 2014). According to these data,
during these 25 million years of separation the Appalachianand Laramidian tyrannosauroids evolved in isolation. The mostparsimonious interpretation is that the Appalachia tyrannosauroids
are the descendants of ancestors that came from Laramidia during

FIGURE 7. Proximal articular surface of the left metatarsal II. A,
Gallimimus bullatus (interpretive drawing); B, Ornithomimus velox (YPM
VP 0542). Interpretive drawing of associated metatarsals II, III and IV.
C, Gallimimus bullatus; D, Ornithomimus velox (YPM VP 0542). Not toscale.

35

the middle Cenomanian or perhaps during the Aptian.
For the most part, the vertebrate faunas, particularly thedinosaurian faunas, are poorly known and understood fromthe Cretaceous of eastern North America (Appalachia). The
Merchantville fauna is thought to represent a mixture of terrestrial
and lagoonal environments (Baird and Galton, 1981; Robb,
2004). Regardless, it seems apparent that these animals would
have been living near the shoreline of the western Atlantic Oceanin eastern Appalachia. Indeed, many of the vertebrates known
from the Merchantville Formation convey a lagoonal or marine
environment, including the chondrichthyans, osteichthyans, andmosasaurs. Pterosaurs, as volant animals, could easily be found inmany environments, although marine and nearshore environments
tend to be better localities to preserve their remains. The skeletal
remains of turtles and crocodylians are expected in such anenvironment. While the dinosaurian fauna is minimal and rare, thepresence of the Merchantville tyrannosauroid with hadrosaurids
adds new information to the paleoecology of eastern Appalachia
during the early Campanian. Hadrosaurids and tyrannosauroids
were widespread throughout North America during the Late
Cretaceous. The rarity of dinosaur specimens from these units ineastern North America makes each potentially more important anduseful for understanding the evolution and paleobiogeography ofthese animals.
ACKNOWLEDGMENTS
We thank Daniel L. Brinkman for access to the specimens in
the collections of Yale Peabody Museum of Natural History in
New Haven, Connecticut. Many thanks go to Roger B. J. Benson
for providing pictures of Dryptosaurus aquilunguis. We also
wish to extend our special gratitude to Jun A. Ebersole, Brandon
Peecook, Tracy J. Thomson, and Steven L. Wick for sharing
photographs of tyrannosauroid metatarsals and for the permission
to use them in this study. We thank Kenneth Carpenter for his
review and comments on the first version of this paper, which
greatly improved its content. The paper benefited from reviewsby Soki Hattori (Fukui Prefectural Dinosaur Museum) and W.
Scott Persons IV (University of Alberta). Lastly, we thank Ralph
Johnson and Ray Meyer for the discovery of these important
specimens and John R. Horner for bringing them to our attention.
REFERENCES
Baird, D., and P. Galton. 1981. Pterosaur bones from the Upper
Cretaceous of Delaware. Journal of Vertebrate Paleontology 1:
67–71.
Baird, D., and J. R. Horner. 1977. A fresh look at the dinosaurs of
New Jersey and Delaware. New Jersey Academy of Science
Bulletin 22: 50A.
Blakey, R. C. 2014. Paleogeography and paleotectonics ofthe Western Interior Seaway, Jurassic-Cretaceous of North
America. Tulsa Geological Society Luncheon Meeting
1–72 pp. (www.searchanddiscovery.com/documents /2014/
30392blakey/idex_blakey.pdf)

36

SEBASTIAN G. DALMAN, STEVEN E. JASINSKI AND SPENCER G. LUCAS

Brochu, C. A. 2003. Osteology of Tyrannosaurus rex: insightsfrom a nearly complete skeleton and high-resolution computed
tomographic analysis of the skull. Journal of Vertebrate
Paleontology Memoir 22: 1–138.
Brusatte, S. L., R. B. J. Benson and M. A. Norell. 2011. The
anatomy of Dryptosaurus aquilunguis (Dinosauria: Theropoda)
and a review of its tyrannosauroid afﬁnities. American Museum
Novitates 3717: 1–53.
Brusatte, S. L., and T. D. Carr. 2016. The phylogeny andevolutionary history of tyrannosauroid dinosaurs. Scientific
Reports, 6:20252/DOI:10.10138/srep20252.
Brusatte, S. L., T. D. Carr and M. A. Norell. 2012. The osteologyof Alioramus, a gracile and long-snouted tyrannosaurid(Dinosauria: Theropoda) from the Late Cretaceous ofMongolia. Bulletin of the American Museum of Natural
History 366: 1– 197.
Brusatte, S. L., M. A. Norell, T. D. Carr, G. M. Erickson, J. R.
Hutchinson, A. M. Balanoff, G. S. Bever, J. N. Choiniere, P. J.
Makovicky and X. Xu. 2010. Tyrannosaur paleobiology: newresearch on ancient exemplar organisms. Science 329: 1481–
1485.
Carpenter, K., M. Clifford and K. Cloward. 2005a. New small
theropod from the Upper Jurassic Morrison Formation of
Wyoming; pp. 23–48 in Carpenter, K., (ed.), The Carnivorous
Dinosaurs. Indiana University Press, Bloomington andIndianapolis, Indiana.
Carpenter, K., C. Miles, J. H. Ostrom and K. Cloward.
2005b. Redescription of the small maniraptoran theropods
Ornitholestes and Coelurus from the Upper Jurassic Morrison
Formation of Wyoming; pp. 49–71 in Carpenter, K., (ed.), The
Carnivorous Dinosaurs. Indiana University Press, Bloomington
and Indianapolis, Indiana.
Carpenter, K., D. Russell, D. Baird and R. Denton. 1997.
Redescription of the holotype of Dryptosaurus aquilunguis(Dinosauria: Theropoda) from the Upper Cretaceous of New
Jersey. Journal of Vertebrate Paleontology 17: 561–573.
Carr, T. D., and T. E. Williamson. 2010. Bistahieversor sealeyi,gen. et sp. nov., a new tyrannosauroid from the New Mexicoand the origin of deep snouts in Tyrannosauroidea. Journal of
Vertebrate Paleontology 30: 1–16.
Carr, T. D., T. E. Williamson and D. R. Schwimmer. 2005. A new
genus and species of tyrannosauroid from the Late Cretaceous(Middle Campanian) Demopolis Formation of Alabama.
Journal of Vertebrate Paleontology 25: 119–143.
Carr, T. D., T. E. Williamson, B. B. Britt and K. Stadtman. 2011.
Evidence for high taxonomic and morphometric tyrannosauroid
diversity in the Late Cretaceous (Late Campanian) of theAmerican Southwest and a new short-skulled tyrannosaurid
from the Kaiparowits Formation of Utah. Naturwissenschaften
doi:10.1007/s00114-011-0762-7.
Carrano, M. T., and J. R. Hutchinson. 2002. Pelvic and hindlimbs
musculature of Tyrannosaurus rex (Dinosauria: Theropoda).
Journal of Morphology 253: 207–228.
Carrano, M. T., J. R. Hutchinson and S. D. Sampson. 2005. New
information on Segisaurus halli, a small theropod dinosaur

from the Early Jurassic of Arizona. Journal of Vertebrate
Paleontology 25: 835–849.
Cifelli, R., J. I. Kirkland, A. Weil, A. L. Deino and B. Kowallis.
1997. High-precision 40Ar/39Ar geochronology and theadvent of North America’s Late Cretaceous terrestrial fauna:
Proceedings of the Natural Academy of Science USA 94:
11163–11167.
Cifelli, R., R. L. Nydam, J. D. Gardner, A. Weil, J. G. Eaton,
J. I. Kirkland and S. K. Madsen. 1999. Medial Cretaceous
vertebrates from the Cedar Mountain Formation, Emery
County, Utah: the Mussentuchit local fauna; pp. 219–242 inGillette, D. D., (ed.), Vertebrate paleontology in Utah. Salt
Lake City, Utah. Utah Department Natural Resources.
Curran, H. A. 1985. The trace fossil assemblage of a Cretaceousnearshore environment: Englishtown Formation of Delaware,
U.S.A.; pp. 261–276 in Curran, H. A., (ed.), Biogenic
Structures. Society of Economic Paleontologists andMineralogists Special Publication 35, Tulsa.
Currie, P. J. 2003. Cranial anatomy of tyrannosaurid dinosaurs
from the Late Cretaceous of Alberta, Canada. Acta
Palaeontologica Polonica 48:191–226.
Currie, P. J. 2005. Theropods, including birds; pp. 367–397 in
Currie, P. J., and Koppelhus, E. B., (eds.), Dinosaur Provincial
Park, A Spectacular Ecosystem Revealed. Indiana University
Press, Bloomington and Indianapolis, Indiana.
Dalman, S. G., A. K. Cantrell, T. L. Suazo and S. G. Lucas. 2016.
First record of a tyrannosaurid theropod (Dinosauria) fromthe lower Campanian Menefee Formation, New Mexico. New
Mexico Geological Society Proceedings Volume, 2016 Annual
Spring Meeting, Macey Center, New Mexico Tech, Socorro,NM, p. 16A.
Dalman, S. G., and S. G. Lucas. 2015. New data on thetyrannosaurid theropods from the middle Campanian lower
Judith River Formation of north-central Montana; pp. 77– 89 in
Sullivan, R. M., and Lucas, S. G., (eds.), Fossil Record 4. New
Mexico Museum of Natural History and Science Bulletin 67.
Dalman, S. G., and S. G. Lucas. 2016. Tyrannosaurid teeth fromthe Claggett Formation of the Elk Basin, Late Cretaceousof Western North America; pp. 83–89 in Khosla, A., andLucas, S. G., (eds.), Cretaceous Period: Biotic Diversity and
Biogeography. New Mexico Museum of Natural History and
Science Bulletin 71.
Eaton, J. G., R. L. Cifelli, J. H. Hutchinson, J. I. Kirkland andJ. M. Parrish. 1999. Cretaceous vertebrate faunas from the
Kaiparowits Plateau, South- Central Utah; pp. 345–353 inGillette, D. D., (ed.), Vertebrate paleontology in Utah. Salt
Lake City, Utah. Utah Department Natural Resources.
Fiorillo, A. R., and R. S. Tykoski. 2014. A diminutive newtyrannosaur from the top of the world. PLOS ONE 9: e91287.
Gallagher, W. B. 1993. The Cretaceous/Tertiary mass extinction
event in the northern Atlantic Coast Plain. The Mosasaur 5:
75–154.
Gallagher, W. B. 2004. Late Cretaceous dinosaurs from New
Jersey and Delaware: stratigraphy, taphonomy and depositional
environments. Geological Society of America, Abstracts withFIRST RECORD OF TYRANNOSAUROID FROM DELAWARE, USA

Programs 36: 117A.
Gallagher, W. B. 2005. Recent mosasaur discoveries from New
Jersey and Delaware, USA: stratigraphy, taphonomy andimplications for mosasaur extinction. Netherlands Journal of
Geosciences 84: 241–245.
Garrison, R. Jr., D. Brinkman, D. J. Nichols, P. Layer, D.
Burge, D. Thayn. 2007. A multidisciplinary study of theLower Cretaceous Cedar Mountain Formation, Mussentuchit
Wash, Utah: a determination of the paleoenvironment andpaleoecology of the Eolambia caroljonesa dinosaur quarry.
Cretaceous Research 28: 461–494.
Hattori, S. 2016. Evolution of the hallux in non-avian theropod
dinosaurs. Journal of Vertebrate Paleontology 36: e1116995.
Holtz, T. R. Jr. 1994. The arctometatarsalian pes, an unusual
structure of the metatarsus of Cretaceous Theropoda(Dinosauria: Saurischia). Journal of Vertebrate Paleontology
14: 480–519.
Horner, J. R. 1979. Upper Cretaceous dinosaurs from the Bearpaw
Shale (Marine) of south-central Montana with a checklist ofUpper Cretaceous dinosaur remains from marine sediments inNorth America. Journal of Paleontology 53: 566–577.
Kirkland, J. I., B. Britt, D. L. Burge, K. Carpenter, R. Cifelli, F.
DeCourten, J. Eaton, S. Hasiotis and T. Lawson. 1997. Lower
to Middle Cretaceous dinosaur faunas: a key to understanding
35 million years of tectonics, evolution, and biogeography.
Brigham Young University Geological Study 42: 69–103.
Krumenacker, L. J., D. Jade Simon, G. Scofield and D. J.
Varricchio. 2016. Theropod dinosaurs from the AlbianCenomanian Wayan Formation of eastern Idaho. Historical
Biology 29: 170–186.
Larson, D. W. 2008. Diversity and variation of theropod dinosaur
teeth from the uppermost Santonian Milk River Formation(Upper Cretaceous), Alberta: a quantitative method supporting
identification of the oldest dinosaur tooth assemblage in
Canada. Canadian Journal of Earth Sciences 45: 1455–1468.
Lauginiger, E. M. 1988. Cretaceous fossils from the Chesapeakeand Delaware Canal: a guide for students and collectors.
Delaware Geological Survey, Special Publication 18: 1–61.
Lehman, T. M., and S. T. Wick. 2012.Tyrannosauroid dinosaurs
from the Aguja Formation (Upper Cretaceous) of Big Bend
National Park, Texas. Earth and Environmental Science
Transactions of the Royal Society of Edinburgh 103: 1–15.
Loewen, M. A., R. B. Irmis, J. W. Sertich, P. J. Currie and S. D.
Sampson. 2013. Tyrant dinosaur evolution tracks the rise andfall of Late Cretaceous oceans. PLOS ONE 8: e79420.
Marsh, O. C. 1877. Notice of a new gigantic dinosaur. American
Journal of Science 114: 87–88.
Marsh, O. C. 1881. Principal characters of American Jurassic
dinosaurs Part V. American Journal of Science, Series 3, 21:
417–423.
Osborn, H. F. 1916. Skeletal adaptations of Ornitholestes,
Struthiomimus, Tyrannosaurus. Bulletin of the American
Museum of Natural History 35: 733–771.
Osmólska, H., E. Roniewicz and R. Barsbold. 1972. A new
dinosaur, Gallimimus bullatus n. gen., n. sp. (Ornithomimidae)

37

from the Upper Cretaceous of Mongolia. Palaeontologica
Polonica 27: 103–143.
Owen, R. 1842. Report on British Fossil Reptiles. Part II. Reportsof the British Association for the Advancement of Science 11:
60–204Owens, J. P., J. P. Minard, N. F. Sohl and J. F. Mello. 1970.
Stratigraphy of the outcropping post-Magothy Upper
Cretaceous formations in southern New Jersey and northern
Delmarva Peninsula, Delaware and Maryland. United States
Government Printing Ofﬁce, Washington, 60 pp.
Parrish, J. M. 1999. Dinosaur teeth from the Upper Cretaceous(Turonian–Judithian) of southern Utah; pp. 319–321 in Gillette,
D. D., (ed.), Vertebrate Paleontology in Utah. Salt Lake City,
Utah. Utah Department Natural Resources.
Peecook, B. R., J. A. Wilson, R. Hernández-Rivera, M.
Montellano-Ballesteros and G. P. Wilson. 2014. Firsttyrannosaurid remains from the Upper Cretaceous“El Gallo”
Formation of Baja California, Mexico. Acta Palaeontologica
Polonica 59: 71–80.
Petters, S. W. 1976. Upper Cretaceous subsurface stratigraphy ofAtlantic Coastal Plain of New Jersey. American Association ofPetroleum Geologists Bulletin 60: 87–107.
Ramsey, K. W. 2005. Geologic map of New Castle County,
Delaware: Delaware Geological Survey, University of
Delaware, Newark, DE.
Robb, A. J., III. 2004. Vertebrate fossils from the Upper
Cretaceous (Merchantville Formation: early Campanian)
Graham Brick Yards locality of New Jersey. The Mosasaur 7:
75–88.
Russell, D. A. 1970. Tyrannosaurs from the Late Cretaceousof western Canada. National Museum of Natural Science,
Publications in Paleontology 1: 1–34.
Schwimmer, D. R. 1989. First dinosaur fossils from Georgia,
with notes on additional Cretaceous vertebrates from the state.
Faculty Bibliography. Paper 463: 147–157pp.
Schwimmer, D. R. 2004. Late Cretaceous dinosaurs of the eastern
Gulf Coast, and their relationships with Atlantic Coast taxa.
Geological Society of America, Abstracts with Programs 36:
117A.
Schwimmer, D. R., G. Dent Williams, J. L. Dobie and W. G.
Siesser. 1993. Late Cretaceous dinosaurs from the Blufftown
Formation in western Georgia and eastern Alabama. Journal of
Paleontology 67: 288–296.
Serrano-Brañas, C. I., C. Gutiérrez-Blando, R. Duarte Bigurra andC. M. González-León. 2017. First occurrence of tyrannosaurid
theropods from the Corral de Enmedio Formation (Upper
Cretaceous) Sonora, México. Cretaceous Research 75: 81–93.
Snively, E., and A. P. Russell. 2002. The tyrannosaurid metatarsus:
bone strain and inferred ligament function. Senckenbergiana
Lethaea 81: 73–80.
Snively, E., A. P. Russell and G. L. Powell. 2004. Evolutionary
morphology of the coelurosaurian arctometatarsus: descriptive,
morphometric and phylogenetic approaches. Zoological
Journal of the Linnean Society 142: 525–553.
Tarsitano, S. F., and M. K. Hecht. 1980. A reconsideration of the38

SEBASTIAN G. DALMAN, STEVEN E. JASINSKI AND SPENCER G. LUCAS

reptilian relationships of Archaeopteryx. Zoological Journal of
the Linnean Society 69: 149–182.
Thompson, T. J., R. B. Irmis, and M. A. Loewen. 2013. First
occurrence of a tyrannosaurid dinosaur from the MesaverdeGroup (Neslen Formation) of Utah: Implications for upper
Campanian Laramidian biogeography. Cretaceous Research
43: 70–79.
von Huene, F. R. 1914. Das natürliche System der Saurischia.
Zentralblatt für Mineralogie, Geologie, und Paläontologie B
1914: 154–158.
Walker, A. D. 1964. Triassic reptiles from the Elgin area:
Ornithosuchus and the origin of carnosaurs. PhilosophicalTransactions of the Royal Society of London, B, 248: 53–134.
Weishampel, D. B. 2004. History and signiﬁcance of East Coastdinosaurs. Geological Society of America, Abstracts with
Programs 36: 95A.
Weishampel, D. B. 2006. Another look at the dinosaurs of theEast Coast of North America. Actas de las III Jornadas sobre
Dinosaurios y su Entorno: 129–168.
Weishampel, D .B., P. M. Barret, R. A. Coria, J. Le Loeuff, X.
Xu, X. Zhao, A. Sahni, E. M. P. Gomani and C. R. Noto. 2004.
Dinosaur distribution; pp. 517–606 in Weishampel, D. B.,
Dodson, P., and Osmólska, H., (eds.), The Dinosauria, 2ndedition.
Wick, S. L., T. M. Lehman and A. A. Brink. 2015. A theropod

tooth assemblage from the lower Aguja Formation (early
Campanian) of West Texas, and the roles of small theropod
and varanoid lizard mesopredators in a tropical predator guild.
Palaeogeography, Palaeoclimatology, Palaeoecology 418:
229–244.
Zanno, L. E., and P. J. Makovicky. 2011. On the earliest recordof Cretaceous tyrannosauroids in western North America:
implications for an Early Cretaceous Laurasian interchange
event. Historical Biology: 3952.
APPENDIX 1
Anatomical Abbreviations
dlr, distolateral ridge; dt4, articulation for distal tarsal 4; gls, M.
gastrocnemius pars lateralis insertion scar; hp, hyperextensor pit;
lc, lateral condyle; llf, lateral ligament fossa; llp, lateral ligament
pit; lnIII, lateral notch for the articulation with the“L”– shaped
proximal articular end of metatarsal III; mV, contact withmetatarsal V; mc, medial condyle; mlf, medial ligament fossae;
mlp, medial ligament pit; mnIII, medial notch for the articulation
with the“L”– shaped proximal articular end of metatarsal III;
mt-I, metatarsal I articular surface; M. ta, M. tibialis anterior;
mt-I, metatarsal I articular surface; pmr, posteromedial ridge.