Some Silicified Strophometiacean Brachiopods 

from the Ordovician of Rftntiickyf 

with Gomments on the Genus Piommena

GEOLOGICAL SURVEY PR OFE S SI OKA

Prepared in -cooperation imtk the 

Commonwealth of Kentucky,

Kentucky G&Ditigic&l Surrey

Some Silicified Strophomenacean Brachiopods 

from the Ordovician of Kentucky, 

with Comments on the Genus Pionomena

By JOHN K. POPE

CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF 

KENTUCKY AND NEARBY STATES

Edited by JOHN POJETA, JR.

GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L

Prepared in cooperation with the 

Commonwealth of Kentucky, 

University of Kentucky, 

Kentucky Geological Survey

Descriptions and illustrations of eight species 

of strophomenoid brachiopods; Leptaena 

kentuckiana is described as a new species. 

Pionomena is shown to be an early davidsoniacean 

brachiopod.

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1982
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary

GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Pope, John K.

Some silicified strophomenacean brachiopods from the Ordovician of Kentucky, with comments on the genus Pionomena.

(Contributions to the Ordovician paleontology of Kentucky and nearby states) (Geological Survey professional paper ; 1066-L)

Bibliography: p.

Supt. of Docs, no.: I 19.16:1066-L

1. Strophomenida. 2. Pionomena. 3. Paleontology-Ordovician. 4. Paleontology-Kentucky. I. Pojeta, John.

II. Title. III. Series. IV. Series: Geological Survey professional paper ; 1066-L. 

QE797.S89P66 564'.8 82-600114

For sale by the Distribution Branch, U.S. Geological Survey, 

604 South Pickett Street, Alexandria, VA 22304
CONTENTS

	Page

Abstract _____________________________________________ LI

Introduction _________________________________________— 1

Morphologic and systematic observations ____________________————— 2

Glossary ________________________________—_—_————— 2

Collections and localities _________________________________— 3

Acknowledgments _____________________________—_———— 3

Preservation ___________________________________________ 3

Preparation and techniques _______________________________—_— 4

Preliminary notes on Rafinesquina ________________________________________________ 5

Systematic paleontology _____________________________________ 6

Superfamily Strophomenacea ________________________________ 6

Genus Oepikina _______________________________________________________— 6

Genus Furdtella ________________________________________________________ 17

Genus Tetraphalerella ____________________________________________________ 20

Genus Leptaena _________________________________________________________ 24

Genus Murinella ________________________________________________________ 26

Superfamily Davidsoniacea _________________________________ 26

Genus Pionomena _______________________________________________________ 26

References cited _________________________________________ 29

ILLUSTRATIONS

PLATES 1-3. Oepikina.

4. Tetraphalerella.

5. Furdtella and Murinellal

6. Tetraphalerella and Furdtella.

1. Tetraphalerella, Holtedahlina, Coolinia, and Pionomena.

8. Leptaena.

Page

FIGURES 1-6. Scattergrams of:

1. Length vs. width, and histograms, for Oepikina minnesotensis from

USGS loc. 5078-CO _________________________ L8

2. Length vs. height, and histogram of height, for ventral valves of

Oepikina minnesotensis from USGS loc. 5078-CO _________ 9

3. 45° diagonal measurement vs. width, and histogram of 45° diagonal 

measurement, for Oepikina minnesotensis from USGS loc. 

5078-CO _______________________________ 10

4. Length vs. width, and histograms, for Oepikina minnesotensis from

USGS loc. 7875-CO _________________________ 11

5. Length vs. height, and histogram of height, for ventral valves of

Oepikina minnesotensis from USGS loc. 7875-CO _________ 12

6. 45° diagonal measurement vs. width, and histogram of 45° diagonal 

measurement, for Oepikina minnesotensis from USGS loc. 

7875-CO _______________________________ 13 

7-9. Combined scattergram fields of:

7. Length vs. width for Oepikina minnesotensis from USGS Iocs.

5078-CO and 7875-CO _______________________ 14

8. Length vs. height for Oepikina minnesotensis from USGS Iocs.

5078-CO and 7875-CO _________________________ 15

9. 45° diagonal measurement vs. width for Oepikina minnesotensis from

USGS Iocs. 5078-CO and 7875-CO _________________ 16 

10. Summary of statistics for Oepikina minnesotensis from USGS Iocs. 5078-CO

and 7875-CO _________________________________ 17

in
IV CONTENTS

11. Comparison of combined scattergram fields of length vs. width for Oepikina 

minnesotensis from Kentucky and from the northern Mississippi Valley 

region and comparison of scattergram fields of length vs. width for 0. minnesotensis from Kentucky with published length and width measurements 

of other species of Oepikina ______________________________________ L18

12. Scattergram of the length vs. maximum width of dorsal valves ofPionomena

recens Neuman _______________________________ 29

TABLE

TABLE 1. Localities from which silicified specimens of Oepikina minnesotensis were

recovered in Kentucky ___________________________ L17

SYSTEM OF MEASUREMENT UNITS

The investigations underlying this series of reports were made over a period of years, and distances and stratigraphic measurements appear 

fairly uniformly in English units. Measurements of fossil specimens, on the other hand, follow the long-standing convention of appearing in 

metric units. Because of the dates of the investigations and the amount of resulting data, the English measurements have been retained. Conversions to metric units may be made by using the following conversion table:

To convert English unit: To metric unit: Multiply by:

Mile (mi) Kilometer (km) 1.61

Foot (ft) Meter (m) .305

Inch (in) Centimeter (cm) .394
CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY

SOME SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE 

ORDOVICIAN OF KENTUCKY, WITH COMMENTS ON THE GENUS

PIONOMENA

By JOHN K. POPE1

ABSTRACT

Eight species of silicified strophomenid brachiopods from Ordovician rocks of Kentucky are described in this report. Seven species are 

strophomenaceans, including six from the Middle Ordovician and one, 

Leptaena kentuckiana n. sp., from the Upper Ordovician. Pionomena 

recens Neuman from the Middle Ordovician is referred to the Davidsoniacea. Three of these species also occur in the Middle Ordovician of 

the northern Mississippi Valley region. Rafinesquina is abundant at 

many localities throughout the Middle Ordovician section of Kentucky. 

Other silicified strophomenaceans are rare and have been recovered 

only from the lower part of the Middle Ordovician section of the area.

Oepikinia minnesotensis has a high degree of polymorphism of 

outline shape, profile, and ornament. Some Middle Ordovician species 

heretofore placed in Strophomena are reassigned to Tetraphalerella. 

Fwrcitetta saadHoltedahlina are differentiated only by the presence of 

a prominent fold in adult valves of Holtedahlina because a bifid dorsal 

medial ridge occurs in species of both genera and because the transmuscle ridges of both genera are similar. The possession by Pionomena 

recens of a perideltidium, dentifers, dorsal medial node, and impunctate shell indicates relationship of this genus to the Davidsoniacea.

INTRODUCTION

Eight species of strophomenid brachiopods are 

described in this report. Seven species are strophomenaceans, including six from the Middle Ordovician and one, 

Leptaena kentuckiana n. sp., from the Upper Ordovician. Pionomena recens from the Middle Ordovician is 

referred to the Davidsoniacea. The silicified 

strophomenacean brachiopods from the Middle Ordovician of Kentucky, except for Rafinesquina, show 

remarkably low species diversity and occur at few 

localities in generally small numbers of individuals. Indeed, only 12 collections of silicified fossils from the Middle Ordovician rocks of Kentucky contain identifiable

'Miami University, Oxford, Ohio 45056.

strophomenaceans other than Rafinesquina, whereas 

more than 120 collections contain specimens of Rafinesquina. The paucity of strophomenaceans other than 

Rafinesquina contrasts sharply with the abundance and 

diversity of these brachiopods in the Upper Ordovician 

rocks of the region. Rafinesquina is so abundant and 

widespread in the Middle Ordovician rocks of Kentucky 

that this genus is not dealt with in this report and is 

under continuing investigation.

Only the High Bridge Group and the lower 

stratigraphic units of the Lexington Limestone contain 

silicified strophomenaceans other than Rafinesquina. 

Although environmental factors during deposition of the 

upper members of the Lexington Limestone and Clays 

Ferry Formation might have suppressed less opportunistic species of this superfamily, it seems more likely 

that the collections are not extensive enough to reveal 

all potential taxa. Two expected well-known 

strophomenacean species from the Middle Ordovician of 

Kentucky, Strophomena vicina Foerste and 

Tetraphalerella auburnensis nasuta (Cooper) 

[= Strophomena incurvata of authors], are not 

represented in the collections.

Species identification has been intentionally conservative so as to enhance the potential usefulness of these 

few strophomenaceans for time correlation and determination of the provincial affinities of the total fauna. 

Although such a small number of species precludes any 

definitive determination of age or provincial affinity, the 

mutual occurrence of three species, Oepikina minnesotensis, Tetraphalerella musculosa, and FurciteUa 

scofieldi, in Kentucky and in the northern Mississippi 

Valley region may be significant. Additionally, distinction of species has been conservative because the writer

Li
L2 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

is convinced that many strophomenacean genera have 

been excessively subdivided at the species level on inadequate morphological criteria. For this region, several 

identifications are tentative, and two unique dorsal 

valves are referred simply to Tetraphalerella sp. and 

Murinellat sp. The new species, Leptaena kentuckiana, 

is based on a few specimens and eventually may be 

shown to be a variant of a previously named species; 

however, on the basis of the present evidence, it is morphologically distinct and is named herein.

MORPHOLOGIC AND SYSTEMATIC OBSERVATIONS

The high degree of polymorphism documented by 

Bretsky and Bretsky (1975) in Oepikina minnesotensis 

(Winchell) from the northern Mississippi Valley region is 

manifest within populations of this species from Kentucky. In particular, 0. minnesotensis shows variability 

in outline shape, profile, and details of ornament, which 

are judged to be inconclusive differentia of species of 

Oepikina. Future studies of large populations of 

Oepikina may indicate some synonymy among presently 

recognized species. The teeth of 0. minnesotensis are 

wide and bear distinctive transverse grooves. Semidenticles on the dorsal surfaces of the teeth are oriented 

perpendicular to the hingeline (pi. 2, fig. Id) and thus 

resemble the true denticles of the early stropheodontids, 

for example, Eostropheodonta.

Provided the type species of Strophomena is accepted 

as S. planumbona (Hall), Tetraphalerella proves to be 

stratigraphically longer ranging and systematically 

more diversified than heretofore recognized. Although 

these genera are superficially homeomorphic, 

Tetraphalerella is distinguished from Strophomena by 

the possession of coarse pseudopuncta, very slender 

teeth, an inclined diductor-muscle bounding ridge, and 

the absence of prominent trans-muscle ridges. Many of 

the Middle Ordovician species presently assigned to 

Strophomena that have been studied for this report actually belong to Tetraphalerella, for example, 

Strophomena aubumensis Fenton, S. basilica Cooper, S. 

costellata Cooper, S. musculosa Fenton, and S. plattinensis Fenton. All the specimens assigned to S. "incurvata" (Shepard) (see discussion in Cooper, 1956, p. 

938-939) that have been examined belong to 

Tetraphalerella. Species of Strophomena s.s. do occur in 

the Middle Ordovician, for example, Strophomena vicina 

Foerste, so that these genera cannot be identified on the 

basis of stratigraphic age.

Furcitella and Holtedahlina are most clearly 

separated by the presence of a prominent fold in adult 

valves of Holtedahlina. Heretofore, Furcitella has been 

distinguished principally by bifurcation of the medial 

ridge of the dorsal valve, but this character also occurs

in immature specimens of H. sulcata (de Verneuil), type 

species of Holtedahlina. The bifid ends of the medial 

ridge of adult specimens of H. sulcata are enlarged to 

form a pair of rounded lobes (pi. 7, figs. 11-12). The dorsal trans-muscle ridges of H. sulcata (pi. 7, fig. 12) are 

more pronounced than those of Furcitella; the absence 

of well-defined trans-muscle ridges in the specimen of H. 

sulcata illustrated by Cooper (1956, pi. 229, B, fig. 8; 

repeated by Williams, 1965, p. H386, fig. 247-lb) is 

anomalous.

Pionomena is assigned to the Davidsoniacea because 

of the presence of a perideltidial area, an orthotetid-type 

socket structure (dentifers), dorsal medial node, and apparently impunctate shell structure. Pionomena is 

assigned provisionally to the family Fardeniidae but differs from Fardenia by having the socket suspended 

above the floor of the valve, as has Gacella (see 

Williams, 1962, p. 222), rather than excavated into the 

shell material.

GLOSSARY

The general morphology of strophomenacean 

brachiopods is well known (Pope, 1976) and is not 

reviewed herein. With few exceptions, standard morphological terms have been used. Radial ornament has 

not been described on all specimens by conventional 

designations such as ramicostellate, parvicostellate, 

etc., because of inconsistency in the patterns of increase 

of costellae of the species described. Crenulations of the 

hinge teeth of strophomenaceans s.s. are called 

"semidenticles" after the usage of Spjeldnaes (1957, p. 

20). Specimens in a recently discovered population of 

Eostropheodonta sp. from Maysvillian rocks of Ohio 

possess both semidenticles and denticles, indicating that 

these structures are not homologues, contrary to 

Spjeldnaes (1957, p. 22). The semidenticles of Oepikina 

minnesotensis (pi. 2, fig. Id) have the position and orientation of the denticles of Eostropheodonta but the size 

and disorganization of the semidenticles of a 

strophomenacean. These features are called semidenticles only by convention. The term "socket buttress 

ridge" (pi. 3, figs. 96, 136, 166; pi. 5, fig. Ic) is retained 

here as a substitute for "socket ridge" in an attempt to 

avoid implication of homology of this structure in 

strophomenaceans to structures of similar function in 

other groups of brachiopods. The posterio-lateral socket 

ridge lies between the socket and the interarea (pi. 3, 

figs. 96,136,166). The posterio-lateral socket ridges are 

accommodated by grooves in the hinge teeth of concavoconvex species or by pockets between the hinge teeth 

and the interarea of resupinate species. The posteriolateral socket ridge has the same function as the outer 

socket ridge of rostrate brachiopods. The dorsal trans-
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L3

muscle ridges (or septa, depending on height) (pi. 3, fig. 

9a; pi. 5, fig. Id; pi. 7, fig. 11) are designated as follows: 

the broad, generally short ridge extending toward the 

anterior from the notothyrial platform is called the 

medial ridge: the narrow, sharply defined breviseptum 

extends anterad from the end of the medial ridge; the 

pair of anterio-medial ridges lies on either side of the 

medial ridge and breviseptum; the posterio-lateral 

ridges are lateral to the anterio-medial ridges. Adventitious ridges or septa (see Pope, 1976, p. 138, fig. 1) 

may be intercalated between the principal trans-muscle 

ridges. The suspended socket structure of Pionomena 

and other davidsoniaceans is called the dentifer (pi. 7, 

fig. 16) following the usage of Cooper and Grant (1974, 

p. 258-259). The term "medial node" (pi. 7, figs. 14-15, 

24, 28-31) is applied to the small bead, rod, or spine on 

the notothyrial platform between the bases of the cardinal process lobes of some davidsoniaceans.

COLLECTIONS AND LOCALITIES

The silicified strophomenids described herein come 

from collections assembled by the U.S. Geological 

Survey. These collections have been assigned locality 

numbers listed in the Cambrian-Ordovician catalog 

(CO). All U.S. Geological Survey locality and collection 

numbers referred to herein, except 5078-CO, are 

documented in parts A (Pojeta, 1979) or K (Parsley, 

1981) of this series. Collection 5078-CO is from the same 

locality, has the same coordinates and section name, and 

comes from the same quadrangle as collection 7875-CO 

(Pojeta, 1979); it is from the Camp Nelson Limestone, 28 

ft. above the base of the section. Most specimens figured 

and discussed have been assigned numbers from USNM 

245277 to 245370 in the U.S. National Museum of 

Natural History catalog. The few illustrated specimens 

that bear "MU" numbers are in the collection of the 

Department of Geology of Miami University, Oxford, 

Ohio.

ACKNOWLEDGMENTS

John Pojeta, Jr., U.S. Geological Survey, generously 

made available the collections studied for this report. F. 

J. Collier lent specimens of Pionomena from the U.S. 

National Museum of Natural History, Washington, B.C. 

The extensive collection of Ordovician brachiopods at 

Miami University, Oxford, Ohio, assembled by the late 

W. H. Shideler, from Minnesota, Wisconsin, Kentucky, 

and Oklahoma, provided comparative specimens for this 

study. Ronald F. Spraitzar and Brian K. Murphy 

assisted respectively with scanning-electron-microscope 

(SEM) observation and photography of Pionomena 

recens and with drafting of graphs. The SEM was made 

available by Thomas K. Wilson of the Department of 

Botany of Miami University. Kenneth G. Wilson, 

Department of Botany, Miami University, reviewed the

graphs of Oepikina minnesotensis. The late Frances T. 

Keyler provided some of the instrumentation for this 

work.

PRESERVATION

All the brachiopods from Kentucky described in this 

report are silicified. Considerable variation in the quality of preservation seems to be related largely to the 

mode of replacement. The replicating mineral is assumed to be quartz, including its cryptocrystalline 

varieties, although this identification has not been 

established definitely by X-ray diffraction. The replacing 

mineral will generally be called "silica" because of lack of 

precise mineralogical identification. Other minerals, 

particularly fluorite, pyrite, and goethite, have been 

observed to replace small parts of a few shells.

Three distinct modes of silicification of shells are 

represented. These varieties of silicification do not seem 

to be taxonomically selective, so I assume that the types 

of silicification are related to factors generally present 

throughout the rocks of a locality and not to factors of 

the microstructure, porosity, or composition of the 

original shells. No substantial evidence has been found 

that indicates the time or environment of silicification.

By far the most common mode of silicification is 

replacement of the external and internal surfaces of 

valves by thin zones of cryptocrystalline silica (pi. 3, fig. 

9; pi. 4, figs. 1, 5). This material is so fine grained and 

brittle that is resembles eggshell or fine bone china. It is 

generally white to light gray, and it breaks sharply and 

smoothly without crumbling.

Single valves preserved by this surface silicification 

are generally hollow and crush quite readily. Bridges or 

columns of coarser quartz crystals may extend between 

the internal and external surface-replacement layers. 

Exceptionally, as in the case of some specimens of 

Rafinesqwina from the upper members of the Lexington 

Limestone, valves are totally replaced by this finegrained silica.

It seems likely that this type of replication was 

regulated simply by the depth to which silica-bearing 

ground water could penetrate into the shell, as if the 

silicification itself formed an impermeable armor. This 

type of replacement does not seem to be related to the 

calcitic microstructure or composition of the original 

shell because the original inner and outer surface layers 

of different species probably would not have had identical micnbstructures and compositions. Internal surfaces and dorsal valves subjectively seem to be better 

preserved by this material than their counterparts.

This mode of replacement, although preserving most 

of the fine detail of the surfaces of valves, is morphologically selective. Cardinal-process lobes are 

generally hollow (pi. 3, fig. 136; pi. 5, fig. Ic) and have
L4 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

conspicuous holes where the myophore areas should be. 

Teeth are hollow and are commonly missing (pi. 6, fig. 

6). The pseudodeltidium commonly is absent. Where 

present, the external dome of the pseudodeltidium 

seems to be constructed of coarse-grained silica. The 

beak of the ventral valve may contain a hole where the 

"root" of the pseudodeltidium was inserted between the 

external shell matter and the secondary shell material 

deposited within the delthyrial chamber (pi. 2, fig. 4b). 

Rather commonly, small areas of valves preserved by 

surface silicification show the concentric welts 

characteristic of beekite replacement (pi. 5, fig. la).

Preservation by saccharoidal silica (pi. 4, fig. 6; pi. 7, 

figs. 1-9) is relatively common. Shells preserved in this 

manner tend to be quite porous and fragile because the 

grains are weakly cemented together. Normally, the 

saccharoidal structure is continuous throughout the 

thickness of a single valve. Saccharoidal replacement 

has not been selective of particular sites, shell layers, or 

morphological structures within the valves. Structures 

such as teeth, cardinal-process lobes and the margins of 

valves commonly are absent because of abrasion or percussion of this fragile material. Fine surface details such 

as costellae and growth lines are absent or poorly 

preserved by the saccharoidal silica. Some specimens 

show sparkling overgrowths of fine quartz crystals that 

impart an arenaceous surface texture (pi. 7, fig. 5). 

Areas of shells otherwise preserved by saccharoidal 

silica may show the concentric welts characteristic of 

beekite (pi. 7, fig. 2).

Total replacement of shells by beekite (pi. 2, fig. 6; pi. 

3, figs. 1-3; pi. 5, fig. 4), that is, chalcedony, is relatively 

uncommon. Such shells are generally strong and resistant to abrasion. Most specimens preserved by this 

material are white to light gray, although some show the 

blue color of chalcedony. Specimens preserved by 

beekite lack fine surface detail so that features such as 

costae, growth lines, and markings of the muscle scars 

cannot be observed adequately (pi. 5, fig. 7). Larger 

structures such as cardinal-process lobes, teeth, and 

muscle bounding ridges tend to be distorted. Preservation by beekite involves the entire shell; that is, such 

preservation is not restricted to certain morphological 

structures or shell layers. A few chalcedony steinkerns 

are present in the collections; none are figured. Their 

lack of surface detail makes identification quite uncertain.

On small areas of some valves of Oepikina and 

Rafinesquina is a very thin, white to light-gray coating 

of flexible, presumably organic, material. These 

coatings have the physical characteristics of thin paper 

and seem to be constructed from a felt of fine fibers. 

This material normally adheres very tightly and is unnoticed until an attempt is made to clean the shells for

photography. Fibers and debris may be attached to 

these papery sheets, which are lifted as the foreign matter is removed. This material seems to be attached most 

often to the internal surfaces of valves, perhaps because 

it peels more readily from the smoother internal surfaces. The origin of this papery material is unknown, but 

the material may be modern because of its light color, 

that is, lack of carbonization. It may be an organic 

residue liberated from the limestone by the etching bath 

and not flushed from the surface of the specimens. It is 

probably not organic matter originally incorporated in 

the brachiopod shells and excluded during silicification, 

nor is it likely to be an altered remnant of brachiopod 

soft tissue.

PREPARATION AND TECHNIQUES

The silicified strophomenacean brachiopods were 

prepared in the Washington laboratory of the U.S. 

Geological Survey by the process outlined by Neuman 

(1967, p. A2) and Pojeta (1979). Most of the specimens 

were liberated by digestion of the limestone in 

commercial-grade hydrochloric acid diluted 10 parts 

water to 1 part acid. Small samples from many localities 

were separately digested in diluted glacial acetic acid to 

recover phosphatic fossils and also to determine 

whether etching in acetic acid would produce specimens 

superior to those processed in hydrochloric acid. The 

silicified fossil residues that had been processed in acetic 

acid were dyed pink for identification.

Comparison of strophomenacean specimens from the 

same localities processed in these different acids reveals 

that no apparent advantage is gained by digestion in 

acetic acid. If anything, the specimens prepared in 

hydrochloric acid have less clinging mud and sand-sized 

particles than those processed in acetic acid. Whether 

this difference is related to more vigorous effervescence 

of the limestone digested in hydrochloric acid, to more 

thftrough rinsing of the greater volume of residue processed in hydrochloric acid, or to the conspicuous dark 

pink of porous debris adhering to specimens processed 

in acetic acid cannot be determined. This difference is 

significant because these silicified specimens are so 

fragile that handling must be minimized, and secondary 

washing of specimens invariably leads to some 

breakage.

Most broken specimens have been repaired with polyvinyl resin (white) cement. This cement may be dissolved 

by prolonged soaking in warm water but generally is not 

softened by brief immersion of the specimens in water, 

as is necessary after photography. Specimens are 

mounted on heavy cardboard panels by means of 

acetone-soluble cement, and the panels are appropriately labeled. Specimens may be examined attached to the
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L5

panels, thereby minimizing breakage, but the cement 

may be removed by use of acetone, without disturbing 

repairs made with the polyvinyl resin cement. Some 

small specimens, for example, the photographed specimens of Pionomena recens Neuman, were mounted on 

straight pins by means of acetone-soluble cement and 

were pinned to styrofoam sheets for storage.

Specimens have not been hardened, except inadvertently by saturation with the acetone-cementmounting solution. Experimental hardening of a few 

specimens resulted in a loss of crisp surface detail, which 

reduced their value for photography.

All specimens were coated with ammonium chloride 

for photography. Dying or staining the specimens to 

render them opaque proved unnecessary. Although 

many of the specimens are translucent, all were 

photographed above a nonreflective black-velvet 

background so that little if any light was transmitted up 

through the specimens to disturb the appearance of the 

surface.

These silicified specimens are too fragile to be 

measured by calipers. All length and width measurements were made from accurately calibrated 

photographs or from images of the specimens produced 

by an opaque projector set at a known magnification. 

Height measurements were made from photographs or 

by means of a very light pivoted rod in the form of a 

first-class lever accurately set to produce height 

magnification of a known amount.

These specimens are so fragile that all except those 

replaced by solid chalcedony must be manipulated only 

with thin flexible forceps. Mud and adhering sand were 

lightly brushed from specimens under water. Removal 

of lint presented a serious problem. Lint fibers cling 

tenaciously to the rough silica surfaces and also seem to 

be electrostatically attracted to some specimens. Lint 

fibers could be removed only by patient brushing and 

picking with forceps. Removal of lint by burning resulted in exfoliation and darkening of some specimens 

and should not be attempted. Because of the lint problem, these specimens should not be packaged in loose 

cotton, sawdust, or finely granular styrofoam. Sheet 

foam rubber seems to be the best packaging and storage 

medium. Attempts should not be made to remove masses of silicified matrix or fossil debris fused to specimens 

because this usually leads to fracture of the specimen.

PRELIMINARY NOTES ON RAFINESQUINA

The strophomenacean brachiopods in the silicified 

fossil residues from the Middle Ordovician of Kentucky 

are dominated by the genus Rafinesquina. More than

5,700 specimens belonging to this genus have been 

recovered from 121 localities. Time has not permitted 

numerical analysis of these specimens, which is essential 

in order to distinguish the subtly differing species of this 

genus. In addition, redescription of Middle Ordovician 

forms should await the conclusion of the revision of Late 

Ordovician species, which is nearing completion, by 

William Harmon of the University of Cincinnati.

The collections from Kentucky that have yielded 

Rafinesquina range stratigraphically from near the base 

of the Lexington Limestone in the Curdsville Limestone 

Member upward through the Clays Ferry Formation 

and into the Cincinnatian Provincial Series. Rafinesquina was not found in the High Bridge Group, below 

the Lexington Limestone, where its ecological position 

may have been occupied by Oepikina.

Forms resembling Rafinesquina trentonensis (Conrad) 

occur throughout the Lexington Limestone. In large collections from the Lexington Limestone, individuals 

show considerable variation of size, shape, and ornament. Biometric analysis is needed to determine 

whether the large specimens in these populations should 

be referred to R. trentonensis or to later species 

characterized by larger size and low convexity, such as 

R. unnchesterensis filistriata Foerste, R. altemistriata 

(Hall), or R. fracta (Meek).

Some of the populations from the Grier Limestone and 

Tanglewood Limestone Members of the Lexington' 

Limestone and from the overlying Clays Ferry Formation are dominated by specimens resembling R. winchesterensis filistriata. Specimens resembling R. winchesterensis winckesterensis Foerste are nowhere abundant in the silicified populations but appear as rare, exceptionally elongate forms in large collections of R. winchesterensis filistriata. Inexplicably, R. winchesterensis 

winchesterensis is relatively common in collections of 

calcareous specimens from the Millersburg Member of 

the Lexington Limestone. Large specimens with coarse, 

strongly differentiated costellae, tentatively referred to 

R. alternistriata, are not abundant and generally do not 

occur with specimens referred to other species. Such 

specimens have been observed in collections from the 

Millersburg and Tanglewood Limestone Members of the 

Lexington Limestone and from the Point Pleasant 

Tongue of the Clays Ferry Formation. Silicified specimens referable to R. ponderosa (Hall) are abundant in 

collections from the Millersburg Member. Specimens 

resembling R. declivis (James) are absent from all the 

collections except that from USGS loc. 7823-CO, in the 

lower part of the Tanglewood Limestone Member near 

Monterey, where ventral valves, but not dorsal valves, 

of this distinctively subtriangular species are common.
L6 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

SYSTEMATIC PALEONTOLOGY

Phylum BRACHIOPODA Dumeril

Class ARTICULATA Huxley

Order STROPHOMENIDA Opik

Suborder STROPHOMENIDINA Opik

Superfamily STROPHOMENACEA King

Family OEPIKINIDAE Sokolskaya, 1960

(nom. transl., emended, Pope, 1976)

Genus OEPIKINA Salmon, 1942

1942. Opikina Salmon, Jour. Paleontology, v. 16, no. 5, p. 589-591. 

[pars] Rafinesquina, of authors.

Type species.-Opikina septata Salmon, 1942, Jour. 

Paleontology., v. 16, no. 5, p. 591-592, by original 

designation.

Diagnosis.- Outline shield-shaped; profile concavoconvex. Ornament finely and generally unequally parvicostellate. Pseudodeltidium arched, small; foramen 

minute or sealed. Pseudopuncta very fine and densely 

distributed. Teeth strong, blunt, semidenticulate; 

generally transversely grooved. Dental plates short. 

Notothyrial platform low and anchor-shaped. Medial 

ridge low and wide; breviseptum long. Two pairs of 

prominent trans-muscle ridges. Dorsal valve with conspicuous marginal rim.

Oepikina minnesotensis (Winchell), 1881

Plate 1, figures 1-14; plate 2, figures 1-12; 

plate 3, figures 1-19; text-figures 1-11.

1881. Strophomena minnesotensis Winchell, Minnesota Geol. and Nat.

History Survey, Ninth Ann. Rept, for 1880, p. 120-122. 

1895. Rafinesquina minnesotensis Winchell and Schuchert,

Minnesota Geol. and Nat. History Survey, Final Rept., v. 3,

pt. 1, p. 401-403, pi. 31, figs. 25-26, 29. 

1942. 0. minnesotensis Salmon, Jour. Paleontology, v. 16, no. 5, p.

592-593, pi. 87, figs. 5-11. 

1956. 0. minnesotensis, Cooper, Smithsonian Misc. Colln., v. 127, p.

914, pi. 245, D, figs. 21-28. 

1975. 0. minnesotensis Bretsky and Bretsky, Geol. Soc. America

Mem. 142, p. 9, 18, pis. 1-2.

Diagnosis. - Shells relatively small. Outline semicircular, slightly transverse or slightly elongate. Cardinal 

extremities orthogonal, rounded, or slightly alate. Convexity variable, low and smoothly curved to high with 

rounded geniculation. Costellae fine, uniform to weakly 

unequal. Teeth strong, transversely grooved. Diductor 

muscle scars oval, slightly impressed. Ventral adductor 

muscle scars on elongated ridges. Ventral valve with 

low submarginal rim. Dorsal trans-muscle ridges 

straight or with slight angular bend; highest toward 

anterior. Marginal rim of dorsal valve conspicuous.

Description. - Outline variable, generally slightly 

wider than long, rarely elongate (pi. 1, fig. 3a) or nasute 

(pi. 1, fig. 13). Cardinal extremities orthogonal or slightly rounded (pi. 1, fig. 86), rarely alate (pi. 1, fig. 12a). 

Convexity variable, from low and nongeniculate to

highly domed, to high with rounded geniculation (pi. 1, 

figs. Ic, 4c, 5c). Lateral margin slightly sinuous. 

Costellae fine, uniform in height (pi. 2, fig. 11) to irregularly unequal (pi. 2, fig. 12). Costellae along margin 

of ventral valve coarser (28-30 per 5 mm) than along 

margin of dorsal valve (34-36 per 5 mm) (pi. 2, figs. 

10-12). Posterio-lateral rugae rare (pi. 1, fig. 10). Prominent growth interruptions common (pi. 1, figs. 86, 96), 

correspond to position of geniculation. Pseudodeltidium 

small, flattened; medial groove. Supra-apical foramen 

small and sealed. Chilidium small, think and folded into 

cleft between cardinal process lobes (pi. 3, fig. 96).

Teeth large and blunt, with deep transverse grooves 

and semidenticles (pi. 2, fig. Id). Dental plates thick, 

short; merge into margin of diductor muscle scar. Pedicle callist bilobed (pi. 2, figs. Id, 46). Diductor muscle 

scar oval to lanceolate; impressed into shell; radially 

ridged (pi. 2, figs. 36, 5, 6). Adductor muscle scars oval, 

at posterior ends of elongated ridges (pi. 2, figs. 5, 6). 

Adductor muscle ridges separated by a fine sharp ridge 

(pi. 2, fig. 5). Ventral valve with low submarginal rim (pi.

2. figs. 16, 5). Ventral interior finely papillose. 

Cardinal process lobes stout, erect hemicylinders (pi.

3. figs. 1, 5, 9a). Myophores triangular, deeply cupped, 

facing posterior (pi. 3, figs. 96,136,166). Socket buttress 

ridges short, thick, and recurved; sockets defined on 

posterio-lateral margin by a short sharp ridge (pi. 3, figs. 

96, 136, 166). Notothyrial platform low and indistinct; 

medial ridge broad and low; breviseptum thin, sharp, 

and long (pi. 3, fig. 9a). Trans-muscle ridges thin, 

straight, or with slight angular bend; highest toward 

anterior ends (pi. 3, figs. 8, 9a, 13a). Adductor muscle 

scars indistinct. Circular submarginal rim variable in 

height, generally conspicuous (pi. 3, figs. 1, 2, 11, 13a). 

Internal surface finely papillose, with widely spaced endospines (pi. 3, fig. 96).

Ontogeny.-Valves of Oepikina minnesotensis from 

Kentucky arranged in a sequence of increasing size, 

presumably from juvenile to adult, do not show marked 

change of outline shape throughout the sequence. The 

cardinal extremities, which generally are angular or 

slightly alate in small valves (pi. 1, fig. 126; pi. 3, fig. 14), 

tend to be rounded in larger valves, perhaps partly 

because of abrasion. The convexity of small valves is 

consistently low and smoothly curved (pi. 1, figs. 126, 

146). As a generality, the height of valves increases with 

increasing shell size, although a few relatively large 

valves have low convexity (pi. 2, fig. 3). The distance 

from the beak to the point of geniculation, if present, is 

not consistent. Geniculation does not seem to occur at a 

specific ontogenetic stage.

The costellae of small ventral valves and of the umbonal and central areas of large ventral valves are fine
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L7

and uniform in height (pi. 1, figs. 116, 126, 146). 

Costellae tend to become coarser and irregularly alternating toward the lateral and anterior margins of large 

ventral valves (pi. 1, figs. 26, 36, 66; pi. 2, fig. 12).

Internally, small ventral valves (pi. 2, figs. 76, 86) lack 

the impressed diductor muscle scars and submarginal 

rim found in large valves (pi. 2, figs. 5, 6). Within dorsal 

valves, the socket buttress ridges and the posteriolateral socket ridges are thin and sharply defined (pi. 3, 

fig. 16b). These ridges become progressively thicker as 

valve size increases (pi. 3, fig. 96), and the lateral ends of 

the sockets become closed by the recurved ends of the 

socket buttress ridges. Dorsal valves less than 10-12 

mm long lack a submarginal rim (pi. 3, figs. 12,15). The 

submarginal rim is initiated in valves 10-12 mm long and 

becomes higher and wider as valve size increases.

The relative prominence of the paired trans-muscle 

ridges of the dorsal valve changes ontogenetically. The 

posterio-lateral trans-muscle ridges enlarge first (pi. 3, 

figs. 12, 14,15). The anterio-medial trans-muscle ridges 

subsequently increase in length and height until both 

pairs of ridg'es are about equal in prominence (pi. 3, fig. 

13a). Thereafter, the anterio-medial ridges remain 

prominent, but the posterio-lateral ridges tend to 

become obscure or submerged by shell material (pi. 3, 

figs. 1, 2, 3, 7).

Remarks on morphology.-The teeth of several large 

specimens of Oepikina minnesotensis from Kentucky 

bear semidenticles oriented perpendicular to the 

hingeline (pi. 2, fig. Id). These semidenticles possibly 

have been accentuated by the silicification or etching 

process. The semidenticles are unusual, along with those 

of Strophom^ena vetusta (figured by Pope, 1976, p. 139, 

fig. 4), in being on the dorsal surface of the tooth rather 

than along the delthyrial edge as in Rafinesquina (Pope, 

1976, p. 139, fig. 5) and in many other strophomenaceans. The position of the semidenticles of 0. minnesotensis resembles the position of the denticles of 

Eostropheodonta. The semidenticles of 0. minnesotensis, however, are more irregular in shape, more 

numerous, and more crowded than the denticles of 

Eostropheodtmta, and they do not cause a corresponding 

denticulation of the; dorsal hingeline. The dental crenulations of Oepikina minnesotensis are called "semidenticles" by convention. Whether these semidenticles are 

homologues of the semidenticles of Rafinesquina or of 

the denticles of Eostropheodonta cannot be determined 

from these specimens.

A transverse to oblique groove occurs in the teeth of 

many species of Oepikina, for example, in 0. septata, 0. 

spedosa, 0. varia, and 0. minnesotensis. The groove accommodates the posterio-lateral socket ridge. The 

posterio-lateral socket ridge consequently functioned as 

a secondary tooth. Few other concavo-convex

strophomenaceans have such deeply grooved teeth, so 

this character permits differentiation of fragments of 

Oepikina from other concavo-convex genera such as 

Rafinesquina. Among resupinate species possessing 

prominent posterio-lateral socket ridges, the teeth are 

not grooved; rather, a pocket occurs between the dorsal 

surface of the tooth and the interarea (see Stropkomena 

vetusta (James) in Pope, 1976, p. 138, fig. 1, "ath"; and p. 

139, fig. 4, "aso").

Some specimens of Oepikina in the collections from 

Kentucky are not completely compatible in shape, ornament, or internal morphology with the definition of 0. 

minnesotensis. These unusual specimens are few, occur 

within populations of 0. minnesotensis, and, in some 

places, intergrade through other specimens into 0. minnesotensis. Consequently, these unusual specimens have 

not been identified as other species but are presumed to 

represent morphological extremes of 0. minnesotensis.

The specimen shown on plate 1, figure 3, is quite 

elongate, whereas the specimen shown on plate 1, figure 

9, is rather transverse. The specimen shown on plate 1, 

figure 13, is slightly nasute. The costellae of the 

specimen shown on plate 1, figure 7b are unusually 

uniform. The rugae of the specimen shown on plate 1, 

figure 10, are quite pronounced, and the radial wrinkles 

of the specimen shown on plate 3, figure 15 are unique. 

The large ventral valves shown on plate 2, figures 3-4 

have unusually low convexity. Additionally, the 

specimen of figure 4 has long dental plates, no semidenticles, an obscure diductor muscle field, and a curiously 

smooth internal surface. The dorsal valve shown on 

plate 3, figure 2, is quite large, and the myophores of the 

cardinal process are not as steeply inclined as those of 

other valves.

Polymorphism ofO. minnesotensis. -Variation of size, 

outline shape, and profile are considerable among the 

specimens of Oepikina from USGS Iocs. 5078-CO and 

7875-CO. Indeed, hasty inspection of these collections 

and comparison of morphologically extreme specimens 

within them may lead to the conclusion that several 

species occur, as implied in the previous section. 

However, the specimens of Oepikina from these two 

localities intergrade in size, outline shape, and profile, 

indicating that they are all members of a highly variable, 

that is, polymorphic, species. To depict the amount of 

variation within each collection and to compare the collections, histograms of length, width, height, and the 

45° diagonal radius, as well as scattergrams contrasting 

these dimensions are provided (text-figs. 1-9). Textfigure 10 summarizes these graphs.

Polymorphism has been shown to occur in 

strophomenacean species from other regions. For example, Alexander (1975) documented the polymorphism, 

which he called phenotypic plasticity, of Rafinesquina
L8 

18

CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

i n i i i i i

02468 

NUMBER OF 

INDIVIDUALS

10-1

2^4-^ D i

Z ? 9-J n n n

EXPLANATION

• 1 specimen

® 2 specimens

@) 3 specimens

Total number of 

specimens = 86

II fl I

10 12 14 16 

WIDTH, IN MILLIMETERS

18 20

FIGURE l.-Scattergram and regression line of length vs. width, and histograms of these measurements, for Oepikina minnesotensis from 

USGS loc. 5078-CO. Length was measured from center of hingeline (not from beak) to center of anterior margin to permit measurements 

from separated dorsal and ventral valves to be incorporated into this diagram. Additionally, measurement of length from hingeline to 

anterior margin permits data to be taken from specimens that have broken or abraded beaks. Width shown is maximum width exclusive of 

alae. Width of specimens that have one broken cardinal extremity was measured to midline of valve, and number was doubled to yield 

total width. Columns and tiers of points do not lie along whole-millimeter increments because specimens were measured optically 

magnified x 4.3, and these data were used to construct the scattergram.

"alternata" from the Upper Ordovician of the Cincinnati 

area. He related the phenotypic plasticity to variations 

in the sedimentologic regime. Bretsky and Bretsky 

(1975) documented considerable polymorphism, 

especially of characters describing profile of the valves, 

in populations of 0. minnesotensis and Stropkomena 

plattinensis Fenton from the Platteville Formation of

the northern Mississippi Valley region. Bretsky and 

Bretsky related the morphological variants and level of 

morphological heterogeneity within these species to the 

probable topography of the Plattville sea floor. They 

noted greater morphological uniformity in offshore 

populations and greater morphological variability within 

nearshore populations.
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L9

EXPLANATION 

• 1 specimen 

© 2 specimens

Total number of 

specimens = 42

HEIGHTEN MILLIMETERS

FIGURE 2.-Scattergram of length vs. height, and histogram of height, for ventral valves of Oepikina minnesotensis from 

USGS loc. 5078-CO. See definition of length in caption for figure 1. Height was measured to highest point on valve above 

plane of commissure. One anomalously high individual is not encircled.
L10 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

EXPLANATION 

• 1 specimen 

® 2 specimens

Total number of 

specimens = 86

1

0246 

NUMBER OF 

INDIVIDUALS

10 12 14 16 

WIDTH, IN MILLIMETERS

FIGURE 3.-Scattergram and regression line of 45° diagonal measurement vs. width, and histogram of 45° diagonal measurement, for 

Oepikina minnesotensis from USGS loc. 5078-CO. See definition of width in caption for figure 1. Diagonal measurement is from center of 

hingeline to lateral margin of valve along a line set at 45° to midline. Two anomalously subrectangular valves are not encircled. Otherwise, the scattergram shows that this population is consistent in outline shape.

Selection of individual specimens of 0. minnesotensis 

from both populations suggests extreme variation in 

outline shape, from transverse through equidimensional 

to quite elongate individuals. The scattergrams of 

length vs. width for each population (figs. 1 and 4) 

however, show a reasonable interdependence of these 

dimensions. Comparison of the length-width scattergram fields from both localities (fig. 7) shows considerable overlap but not total conformity of the lengthwidth fields. Figure 7 and the correlation coefficients of 

length-width in figure 10 show that the specimens from 

USGS loc. 7875-CO are more variable in length-width 

relationship than are those from 5078-CO.

Variation within the two collections is also observed 

among specimens that are subrectangular, subcircular, 

or subtriangular in outline. To test the importance of 

these different shapes, scattergrams were constructed 

to contrast the width of specimens against the distance 

from the center of the hingeline to the lateral margin 

along a line set at 45° to the midline (the 45° diagonal 

radius). This relationship for each collection is shown in 

figures 3 and 6, and the two collections are compared in

figure 9. Again, there is a surprising degree of interdependence of these dimensions, but specimens from 

7875-CO are more variable than are those from 

5078-CO. The individuals in the two collections do not 

seem to be divisible into several species on the basis of 

outline shape.

The specimens of 0. minnesotensis from Kentucky 

show greater variability in their height than in other 

dimensions plotted herein. The scattergrams of length 

vs. height, (figs. 2 and 5), which are compared in figure 

8, are rather broad and the correlation coefficients of 

L/H (fig. 10) are somewhat lower than the other correlation coefficients. This relationship corresponds to the 

relationship of dimensions found by Alexander (1975, p. 

611) for Rafinesquina "alternata," where the correlation 

coefficients of length vs. height have considerably lower 

values than those of length vs. width. Similarly, Bretsky 

and Bretsky (1975) found the amount of inflation of the 

valves of 0. minnesotensis from the northern Mississippi 

Valley region to be highly variable. Scattergrams contrasting total length against distance from the beak to 

the initiation of geniculation for 0. minnesotensis from
SILICCFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY Lll

I I I

0 2

I I I I I I I 

463

NUMBER OF 

INDIVIDUALS

I I I I I

10 12 14

< 12 ~ 

9 10- 

5

z 8H

4- 

2- 

0- flnH

EXPLANATION

• 1 specimen

® 2 specimens

"^) 3 specimens

Total number of 

specimens = 94

n n n n

12 14 16 18 

WIDTH, IN MILLIMETERS

20 22

FIGURE 4.-Scattergram and regression line of length vs. width, and histograms of these measurements, for Oepikina minnesotensis from 

USGS loc. 7875-CO. See definitions of length and width in caption for figure 1. One anomalously long specimen is not encircled.

Kentucky, not included herein, have even lower correlation coefficients than those of length vs. height.

In the past, the amount of inflation and the position of 

geniculation of strophomenacean brachiopods has been 

thought to be a diagnostic characteristic of species. The 

beak-to-geniculation dimension may be a diagnostic 

characteristic of angularly geniculate forms such asLeptaena, where other characters such as ornament, 

thickness of the shell matter, and presence of endospines differ on either side of the line of inflection.

Among the shield-shaped less angularly geniculate 

strophomenaceans such as Oepikina, Rafinesquina, 

Strophomena, and Tetrapkalerella, the height of the 

valves and the distance from the beak to the geniculation is variable and should not be relied upon exclusively 

to differentiate species.

The specimens of Oepikina from the two localities also 

show variation in qualitative, that is, subjectively appraised characteristics such as the nature of the 

costellae, size and shape of the cardinal process lobes,
L12 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

• 1 specimen

® 2 specimens

3 specimens

Total number of 

specimens = 41

T

4 6 

HEIGHT, IN MILLIMETERS

FIGURE 5.-Scattergram of length vs. height, and histogram of height, for ventral valves of Oepikina minnesotensis 

from USGS loc. 7875-CO. See definitions of length and height in captions for figures 1 and 2.
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L13

EXPLANATION 

• 1 specimen 

® 2 specimens

3 specimens

4 specimens

Total number of 

specimens = 95

I I I I I I 

6 8 10 12 12 

NUMBER OF INDIVIDUALS

14 16 

WIDTH, IN MILLIMETERS

FIGURE 6.-Scatter|yram and regression line of 45° diagonal measurement vs. width, and histogram of 45° diagonal measurement, 

for Oepikina minnesotensis from USGS loc. 7875-CO. See definitions of width and 45° diagonal measurement in captions for figures 1 

and 3.

height of the marginal rim, shape of the diductor muscle 

scars, and prominence of the dorsal trans-muscle ridges. 

Division of the collections into groups of specimens bearing extreme variations of the above characteristics, for 

example, those having unusually large cardinal-process 

lobes or unusually uniform costellae, does not 

automatically segregate individuals bearing extreme 

variations of outline, profile, or other subjectively appraised characters. Finally, if specimens possessing 

each extreme type of outline shape, profile, or ornament 

were placed in a separate species, at least six sympatric 

species would have to be recognized in the collections 

from USGS Iocs. 5078-CO and 7875-CO. This would be 

ecologically unlikely. Consequently, only one polymorphic species, Oepikina minnesotensis, is recognized in 

these collections.

Comparison.-0. minnesotensis from Kentucky is differentiated from some other species of Oepikina by size 

and length/width ratio (fig. 11, lower diagram). The field 

representing length vs. width for 0. minnesotensis from 

Kentucky (fig. 11, upper diagram) overlaps the plexus of 

points constructed from measurements taken from the 

illustrations of 0. minnesotensis by Bretsky and Bretsky 

(1975).

Several species of Oepikina-0. speciosa Cooper, 0. 

gregaria Cooper, 0. formosa Cooper, and 0. varia 

Cooper-seem generally to lie along the same 

length/width axis and to have approximately the same 

size as 0. minnesotensis. This necessitates differentiation of these species on qualitative characteristics.

0. speciosa is larger than 0. minnesotensis and has a 

more strongly defined notothyrial platform and dorsal 

medial ridge than does 0. minnesotensis. Cooper (1956, 

p. 920) differentiated 0. speciosa from 0. inquassa 

(Sardeson) on beak-to-geniculation distance. Cooper's illustrations of 0. speciosa (1956, pi. 238, figs. 6-7) have a 

strong resemblance to the syntype of 0. inquassa 

figured by Salmon (1942, pi. 87, fig. 14). In turn, these 

specimens resemble those of 0. minnesotensis shown on 

plate 3, figures 2 and 3 of this report. Winchell and 

Schuchert (1895) concluded that Strophomena inquassa 

Sardeson was a variety of Rafinesquina minnesotensis 

(Winchell). These three species might prove to intergrade if larger populations were studied. Regardless 

of how this matter eventually may be resolved, 0. inquassa as presently identified is larger and more subcircular than is 0. minnesotensis and has more conspicuous 

(?gerontic) internal features.
L14 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

14 16 18 

WIDTH, IN MILLIMETERS

20 22

FIGURE 7.-Combined outlines of scattergrams of length vs. width for Oepikina minnesotensis from USGS Iocs. 5078-CO and 7875-CO.

0. gregaria is smoother, has finer costellae, is more 

alate, has more delicate dorsal trans-muscle ridges, and 

has wider socket buttress ridges than does 0. minnesotensis. These species are probably distinct.

0. formosa is distinguished from 0. minnesotensis by 

its sharply defined, somewhat wavering costellae, wide 

socket buttress ridges, and a bifurcation or alveolus at 

the anterior end of the dorsal medial ridge.

0. varia has a small diductor muscle scar, elevated 

notothyrial platform and dorsal medial ridge, and thick, 

short dorsal trans-muscle ridges, which set it apart from 

0. minnesotensis.

0. transitionalis (Okulitch) presents a problem. The 

holotype, a deformed and incomplete ventral valve, does 

not contain enough information to permit recognition of 

the species. It is larger than any specimen of 0. minnesotensis from Kentucky. The plesiotype figured by 

Salmon (1942, pi. 87, fig. 18), a dorsal interior, is only 

slightly larger than the largest 0. minnesotensis and 

might lie within a reasonable extension of the length/

width scattergram of the Kentucky specimens. This 

plesiotype specimen differs from 0. minnesotensis from 

Kentucky by being slightly more subtriangular and alate 

and by having a thickened breviseptum and short thick 

anterio-medial trans-muscle ridges. The position and 

angle of geniculation and amount of alation, according 

to the descriptions of Salmon, should separate these 

species. I am not convinced that these are diagnostic 

characteristics; hence, lacking description of a population of O. transitionalis, I cannot draw a conclusion 

regarding the distinction of these species.

The Oepikina populations.-The collections of 0. minnesotensis from USGS Iocs. 5078-CO and 7875-CO seem 

to be samples of largely biocoenosic populations. In fact, 

the collections possibly represent samples of populations 

that began on the sea floor with one major influx of spat 

and then slowly diminished in numbers because of 

episodic mortality. This conclusion is based upon the 

considerable range of sizes among individuals in both 

populations, especially from loc. 5078-CO, survivorship
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L15

inDC

o

z

LLJ

4 6 

HEIGHT, IN MILLIMETERS

FIGURE 8.-Combined outlines of scattergrams of length vs. height for Oepikina minnesotensis from USGS Iocs.

5078-CO and 7875-CO.
L16 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

c/j 

cc

LU

LU

cc 

D 

C/J <LU

o

CD 

Q

o

in

10

10 12 14 16 18 

WIDTH, IN MILLIMETERS

FIGURE 9.-Combined outlines of scattergrams of 45° diagonal measurement vs. width for Oepikina minnesotensis from USGS Iocs.

5078-CO and 7875-CO.

curves, and what appears to be a repeated pattern of 

growth interruptions on many of the ventral valves.

Despite the fact that many of the specimens in both 

collections are disarticulated, articulated specimens of 

different sizes are found. Size-selective preservation or 

size sorting like that reported by Richards and Bambach 

(1975, p. 777) for Rafinesquina from the Richmondian 

Stage does not seem to have taken place. Simple disarticulation without fragmentation or size sorting of 

strophomenacean brachiopods is not necessarily indicative of long-range transport of the individuals. The 

strophomenacean hinge, with its wide delthyrial angle, 

deltidiodont tooth form (Jaanusson, 1971, p. 36), and 

trough-shaped sockets probably did not lock the valves 

together positively. This permitted the valves to disarticulate with but slight disturbance or overturning after 

death and decay of the adductor muscles. Currents on 

the sea floor where these Oepikina populations lived 

possibly were competent only to overturn the shells but

not to fragment them or to remove at least those in the 

9-18-mm-long size range. (Actually, valves smaller than 

9 mm long occur in both collections, but all these very 

small specimens are incomplete owing to lack of 

silicification of the thin margin of the shell or to fracture 

during or after etching of the shells from the limestone.)

Many of the ventral valves from USGS loc. 5078-CO 

bear a major growth interruption, which delineates a 

central shell region of about the same size (pi. 1, figs. 66, 

86, 96,10,116,126). This growth interruption commonly 

initiates geniculation. On many of the valves, this major 

growth interruption is followed a short distance toward 

the margin by a second, less pronounced interruption. 

These growth interruptions may record the same two 

adverse events in the growth of these individuals.

The histograms for length and width of 0. minnesotensis from 5078-CO (fig. 1) show a rather rhythmic rise 

and fall. These histograms resemble the histogram of 

length presented by Walker and Parker (1976, p. 196) in
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L17

U.S.G.S. loc.

5078-CO

7875-CO

Statistics

Mean 

Standard deviation

„ Variation . .. rioo s~l 1 -^- 1

Mean 

Standard deviation 

Variation f100 sl

L x J

Length

14.22 

2.48 

17.44

14.46 

1.16 

8.02

Width

16.43 

2.48

17.28

16.23 

1.85 

11.39

Height

4.81 

1.46 

30.35

5.06 

1.21 

23.91

45° Diagonal

11.08 

1.96 

17.68

11.55 

1.04 

9.00

U.S.G.S. loc.

5078-CO

7875-CO

Regression line

Slope 

Y intercept 

Correlation coefficient

Slope 

Y intercept 

Correlation coefficient

L/W

0.799 

1.09 

.916

0.422 

7.6 

.0671

L/H

1.05 

10.65 

.848

.616 

11.7 

.667

45°

0.646 

.45 

.936

0.433

4.51 

.768

Diagonal/W

FIGURE 10.-Summary of statistics for Oepikina minnesotensis from USGS Iocs. 5078-CO and 7875-CO. All measurements in millimeters.

their detailed analysis of Strophomena basilica Cooper 

from the Middle Ordovician of Tennessee. The several 

crests of the length and width histograms for 0. minnesotensis probably evidence episodic (seasonal?) mortality in this brachiopod population, just as they do on 

the length histogram for S. basilica.

Size-frequency distribution diagrams for the two 

populations show left-skewed distributions. Survivorship curves for both populations, constructed according 

to the method of Richards and Bambach (1975), are convex. These patterns suggest that both populations were 

subject to low infant mortality and increased mortality 

among ephebic and gerontic individuals. The crests of 

the histograms, thus, should not be interpreted as successive (annual) spatfalls in a population extinguished by 

one event, because such a scenario would yield a large 

proportion of small valves (right-skewed distribution 

diagrams and concave survivorship curves). The alternative model, tha.t of a single large spatfall, followed by

high infant survival, followed by episodic mortality, may 

have been the more likely history of these populations. 

Occurrence and specimens. - Silicified specimens of 0. 

minnesotensis have been recovered from four localities 

in Kentucky (table 1).

Family STROPHOMENIDAE King, 1846 

Subfamily FURCITELLINAE Williams, 1965

Genus FURCITELLA Cooper, 1956

1956. Furcitella Cooper, Smithsonian Misc. Colln., v. 127, pt. 1, p.

875-877. 

[pars] Strophomena, of authors.

Type species.-Furcitella plicata Cooper, 1956, p. 

877-878, by original designation.

Diagnosis.- Shells small; outline transversely semicircular to subrectangular. Profile unequally biconvex. 

Shell not prominently folded. Costellae not prominently 

alternate. Foramen open. Diductor muscle field 

subrhombic; muscle bounding ridge thin, incomplete. 

Medial ridge of dorsal valve bifurcate; trans-muscle 

ridges generally weak, abruptly bent.

TABLE I.-Localities from which silicified specimens of Oepikina minnesotensis were recorded in Kentucky

[USGS Iocs. 5078-CO and 78V5-CO are in the Camp Nelson Limestone near High Bridge, Ky. Loc. 7835-CO is in the Camp Nelson Limestone, along U.S. Route 27,1 mile north of the Kentucky 

River. The exact locality of one specimen is not known, but the specimen is from the High Bridge Group in Kentucky. Figured specimens on plates 1-3 are numbered USNM 245277 to 245318]

USGS loc.

5078-CO

7875-CO

7835-CO

Unknown

No. of ventral valves

78

74

2

0

No. of dorsal valves

57

67

2

0

No. of articulated 

specimens

3

5

1

1

Comments

Plus many fragments. Fine-grained, dense surface silicification.

Plus many fragments. All specimens coarsely silicified

Plus many fragments. All specimens poorly preserved

Coarsely silicified, no ornament
L18 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

EXPLANATION

O. minnesotensis 

(scattergram 

fields from 

5078-CO and 

7875-CO combined)

O. minnesotensis 

(measured from 

Bretsky and

Bretsky, 1975)

1 specimen

2 specimens

EXPLANATION

—— Outline of 5078-CO

—— Outline of 7875-CO

0. eximia 

- 0. formosa

— — — — 0. gregaria

—— _—— 0. tirata

— ———— 0. quadrata

—- — -—-— 0. speciosa

— • — •••— 0. xubplanodorsata

0. varia 

N 0. nasuta

10 12 14 16 18 20 22 24 26

WIDTH, IN MILLIMETERS

28 30 32 34 36

FIGURE II.-A, Comparison of combined scattergram fields of length vs. width for Oepikina minnesotensis from Kentucky 

(indicated by solid line) with measurements of length and width taken from published photographs (Bretsky and Bretsky, 

1975) of O. minnesotensis from the northern Mississippi Valley (Wisconsin, Illinois, Iowa, and Minnesota). B, Comparison of 

scattergram fields of length vs. width for O. minnesotensis from Kentucky with published length and width measurements 

(Cooper, 1956) of other species of Oepikina.
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L19

Description. - Shells small; outline transversely semicircular to subrectangular; cardinal extremities orthogonal. Profile unequally biconvex; dorsal valve more 

uniformly and strongly domed than ventral valve; ventral valve flattened or slightly concave near anterior 

margin. Anterior margin rectimarginate to weakly 

plicate. Ventral interarea moderately long; 

pseudodeltidium arched; chilidium small; foramen open. 

Costellae moderately fine, uniform in width and height; 

growth interruptions common. Surface of valves 

uneven, irregularly undulating. Pseduopuncta fine.

Teeth strong; dental plates short and vertical. Diductor muscle field subrhombic, bounded laterally by thin 

low ridges. Adductor muscle scars long, narrow, slightly 

elevated, and divided by low medial ridge.

Cardinal process lobes low and cupped; notothyrial 

platform short and high. Sockets short, straight, and 

widely divergent. Medial ridge of dorsal valve bifurcate; 

breviseptum faint. Trans-muscle ridges weak, abruptly 

bent.

Remarks. -Furcitella and Holtedahlina are closely 

related, as noted by Cooper (1956, p. 876). These genera 

are distinguished from other closely related genera such 

as Trigrammaria and Microtrypa by their biconvex profiles, open foramina, and uniform costellae, and from 

Murinella by the absence of a marginal flange within the 

dorsal valve. Furcitella and Holtedahlina are differentiated by the presence of a dorsal fold in adult specimens 

of Holtedahlina (pi. 7, figs. 11, 12) and a prominent 

bifurcation of the dorsal medial ridge of adult specimens 

of Furcitella (pi. 5, figs. 2b-d). In reality, immature 

specimens of Holtedahlina sulcata (de Verneuil), type 

species of HoltedcMina, conform to the diagnosis of 

Furcitella. The differences between these genera, consequently, must be regarded as late ontogenetic additions to Holtedahlina. The species of these genera may 

constitute a chronocline extending from the Middle Ordovician through the Upper Ordovician, but at present, 

a deficiency of species from the upper Middle Ordovician 

and lower Upper Ordovician interrupts the speculative 

sequence.

Small specimens of Holtedahlina sulcata do not have a 

dorsal fold and as a result resemble Furcitella in 

anterior view. The fold begins when specimens achieve 

about one-third adult length, becomes higher and 

sharper as size increases (pi. 7, figs. 11-12), and is 

especially pronounced in large individuals that occur in 

clusters. The strength of folding, thus, seems to be 

related to both ontogenetic stage and population density.

The dorsal medial ridge of immature specimens of H. 

sulcata is bifurcate (pi. 7, fig. 10), although the split ends 

are not as long as those of Furcitella (pi. 5, figs. 2b-d). 

The split ends of the medial ridge of H. sulcata are not

ridges set on either side of the anterior termination of 

the medial ridge, as interpreted by Cooper (1956, p. 

876). As shell size increases, the ends of the nieclial ridge 

of H. sulcata progressively enlarge to create a pair of 

closely spaced, rounded lobes (pi. 7, fig. 11) from which 

emerges the breviseptum.

Bifurcation of the medial ridge is not an exclusive attribute of the Furcitellinae; it occurs inconsistently in 

other genera of the Strophomenacea. For example, this 

character is found at least in some species of Dactylogonia, Bellimurina, Cyphomena, Microtrypa, 

Oepikina, Maakina, and Strophomena. The presence of 

the bifurcation seems to be related to the ontogenetic 

stage of specimens, being generally absent or obscure in 

quite small specimens and commonly submerged by shell 

material in unusually large specimens.

The pairs of trans-muscle ridges are not as evident in 

Furcitella as they are in Holtedahlina. Immature 

specimens of Holtedahlina sulcata have sharply defined 

posterio-lateral trans-muscle ridges and obscure 

anterio-medial trans-muscle ridges (pi. 7, fig. 10), the 

condition found in Furcitella. As shell size increases, the 

posterio-lateral trans-muscle ridges of Holtedahlina 

become submerged by shell matter and a lyre-shaped 

pair of anterio-medial trans-muscle ridges develops. The 

anterio-medial trans-muscle ridges arise from nodes adjacent to the lobate ends of the medial ridge (pi. 7, fig. 

11). This produces a transverse row of four nodes, a condition not observed in Furcitella.

Furcitella cf. F. scofieldi (Winchell and Schuchert) 

Plate 5, figures 1-6; plate 6, figures 3-6

1892. Stropkomena scofieldi Winchell, and Schuchert, Am. Geologist,

v. 9, p. 286-287. 

1895. S. scofieldi Winchell, and Schuchert, Minnesota Geol. and Nat.

History Survey, v. 3, pt. 1, Paleontology, ch. 5, p. 398-399, pi.

31, figs. 18-21. 

1956. Furcitella scofieldi Cooper, Smithsonian Misc. Colln., v. 127, pt.

1-2, p. 878, pi. 229, A, figs. 1-5; pi. 265, C, fig. 6, [? fig. 5].

Diagnosis.- Outline transversely subrectangular to 

semicircular. Profile unequally biconvex; ventral valve 

flattened to concave in central region. Anterior commissure weakly uniplicate to undulating. Costellae 

moderately fine, somewhat discontinuous; surface of 

valve irregularly wrinkled. Diductor muscle field oval to 

rhombic. Dorsal medial ridge relatively narrow; transmuscle ridges low, short, abruptly bent.

Description. - Shells small. Outline transversely 

subrectangular (pi. 6, fig. 5) to semicircular; cardinal extremities orthogonal to slightly obtuse and rounded, 

rarely acute. Profile unequally biconvex; dorsal valve 

planate toward posterior, strongly curved to anterior; 

ventral valve gently convex toward posterior, flattened 

to gently concave in central to anterior region. Anterior
L20 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

commissure rectimarginate to weakly uniplicate (pi. 5, 

fig. 3c) to gently undulating (pi. 6, figs. 3a, 56). Costellae 

moderately fine (15 to 16 per 5 mm), closely spaced, 

relatively uniform in height, but tending to be discontinuous and wavering in direction (pi. 5, figs. 2e, 5c; pi. 

6, fig. 3d). Growth interruptions and comae common (pi. 

5, fig. 2a; pi. 6, fig. 6a); surface of valves gently and irregularly wrinkled (pi. 5, fig. la). Pseudodeltidium short, 

gently arched (pi. 6, figs. 3c, 5e); foramen open, 

moderately large, apical (pi. 6, fig. 5d). Chilidium thin, 

protruding, folded into meso-cardinal cleft.

Teeth small but strong and blunt (pi. 6, fig. 5e); dental 

plates vertical to slightly flared, slightly receding (pi. 6, 

fig. 5cQ. Diductor muscle field oval (pi. 6, figs. 5c, 66) to 

rhombic (pi. 6, fig. 3c). Muscle-bounding ridge low, incomplete. Medial ridge of diductor muscle field low and 

short; adductor muscle scars elevated (pi. 6, fig. 3c).

Cardinal process lobes narrow, myophores deeply 

cupped (pi. 5, figs. Ic-e, 2c-d). Meso-cardinal ridge thin, 

low. Notothyrial platform short, high (pi. 5, fig. 16). 

Socket buttress ridges high, short, straight, with reflexed ends (pi. 5, figs. Ib, 26, 46). Medial ridge relatively narrow, short, high, with deeply cleft anterior end (pi. 

5, figs. 2b-d). Breviseptum long and faint. Paired transmuscle ridges low, abruptly bent (pi. 5, figs. 16, d-e). Internal surface of both valves finely papillose, margins 

finely striated.

Remarks.- These specimens from Kentucky differ 

from specimens from Minnesota by the somewhat 

discontinuous and hackly character of the costellae, by 

the irregular wrinkling of the surfaces of the valves, by 

the slightly greater convexity of the largest dorsal 

valve, and by the rhombic shape of the diductor muscle 

field of the largest ventral valve. The differences in 

costellae and the wrinkling of the valves may be preservational or environmental in origin. The greater convexity of the dorsal valve and the rhombic shape of the 

diductor muscle field may be the products of late ontogenetic change. I believe that these differences are 

not great enough to require the erection of a new 

species.

The identity of the specimen referred toF. scofieldi by 

Cooper (1956, pi. 265, C, fig. 5), is questionable. The 

similarity of the trans-muscle ridge system of this 

specimen to the trans-muscle ridges of Microtrypa 

noted by Williams (1962, p. 207) is indeed correct. The 

bifid ends of the medial ridge of this specimen are much 

longer than those found in Furcitella, and the adjacent 

pairs of trans-muscle ridges lack the abrupt bend found 

in Furcitella and Holtedahlina (see pi. 7, figs. 10-13). 

Additionally, the central region and trans-muscle ridges 

of this valve are coarsely papillose, a trait that has not 

been observed in other specimens of Furcitella.

Occurrence, measurements, and specimens. -All 

specimens are from USGS loc. 5078-CO, Camp Nelson 

Limestone near High Bridge, Ky. Specimens include 8 

ventral valves, 5 dorsal valves, 1 small articulated 

specimen, and fragments. The largest ventral valve, if 

complete, would measure about 19 mm wide x 15 mm 

long. A smaller complete ventral valve is 15V2 mm wide 

x 12 mm long. The largest dorsal valve, incomplete, is 

21V2 mm wide. Figured specimens are numbered USNM 

245327-245336.

Several specimens, numbered USNM 245369, from 

USGS loc. 5015-CO, Salvisa Bed of the Perryville 

Limestone Member of the Lexington Limestone near 

Perryville, Ky., superficially resemble F. cf.F. scofieldi. 

These specimens are steinkerns and eroded articulated 

valves preserved in coarse chalcedony (beekite) and consequently cannot be identified with certainty. Mixed 

with these are small resupinate articulated specimens 

referred to Strophomena s.s., numbered USNM 245370. 

These specimens bear traces of alternate costellae and 

fine, randomly arranged pseudopuncta which differentiate them from Tetraphalerella cf. T. costellata. These 

specimens are too poorly preserved to be identified.

SubfamHy STROPHOMENINAE King, 1846 

Genus TETRAPHALERELLA Wang, 1949

1949. Tetraphcderetta Wang, Geol. Soc. America Mem. 42, p. 28-29. 

[pars] Strophomena, of authors.

Type species.-Tetraphalerella cooperi Wang, Geol. 

Soc. America Mem. 42, p. 29-30, original designation.

Diagnosis. - Shells generally large, semicircular to 

subrectangular, resupinate. Parvicostellae fine and 

uniform. Ventral interarea long, apsacline, forming 

sharply acute angle with external surface. Pseudodeltidium long, narrow, smoothly arched to depressed. 

Pseudopuncta coarse, arranged in rows. Teeth slender, 

pointed; dental plates thin, laterally flared. Dorsal surface of teeth not strongly depressed below extension of 

plane of interarea. Diductor muscle bounding ridge inclined. Cardinal process stout, myophores cupped. 

Sockets short, gaping. Trans-muscle ridges obscure to 

absent.

Remarks and comparisons.-Tetraphalerella is differentiated from Trigrammaria, Microtrypa, and Actinomena by the possession of fine uniform costellae and 

the lack of prominent trans-muscle ridges. Additionally, 

Tetraphalerella generally lacks the subtriangular folded 

shape of Trigrammaria, is larger than Microtrypa, and 

is more highly domed than Actinomena.

Tetraphalerella and Strophomena tend to be 

homeomorphic. Wang (1949, p. 29) was correct in com-
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L21

menting that "Tetraphalerella embraces a large group 

of species that have been heretofore assigned to 

Strophomena on thei basis of their convexo-concave profile and other similarities." In fact, the concept of 

Strophomena still understood by many authors is that of 

Tetraphalerella. Fortunately, these genera are not difficult to separate if well-preserved specimens, particularly internal surfaces, are inspected carefully. The 

most conspicuous differences between these genera are 

found in their ventral interareas, teeth, diductor muscle 

bounding ridges, cardinal processes, trans-muscle 

ridges and psesudopuncta. No single character alone, 

perhaps with the exception of the pseudopuncta, 

satisfactorily differentiates these genera.

Any discussion of Strophomena must ultimately depend upon the attributes of S. planumbona (Hall), which 

is presumed to be the type species. Hall and Clarke 

(1892, p. 245-252), Miller (1897), and Nickles (1903, p. 

214-217) have provided detailed comments on the status 

of S. planumbona as type species of the genus. Succeeding authors have generally acknowledged S. 

planumbona as the type species.

Externally, Tetraphalerella and Strophomena are difficult to separate. A. subtle difference is found in the ventral interarea, which in Tetraphalerella is generally 

relatively longer than that of Strophomena and makes a 

more acute angle with the surface of the ventral valve. 

That is, the ventral posterior margin of Tetraphalerella 

often seems unusually sharp. This condition is exceptional in Strophomena, although present in S. vetusta 

(James). The pseudodeltidium of Tetraphalerella is 

generally narrower (left to right) than that of 

Strophomena, and the margins of the delthyrium of 

some species seem somewhat convexly curved, giving 

the pseudodeltidium a sharply pointed appearance (pi. 4, 

figs. 36, 4c£). The pseudodeltidium of Tetraphalerella is 

generally arched, and in some species carinate (pi. 4, fig. 

2a), but it may be flat, medially grooved, or even slightly 

concave.

The teeth of Tetraphalerella are unusual. The teeth of 

young and ephebic individuals, especially of 

stratigraphically older species, tend to be very slender. 

In some specimens, these teeth are no more than 

thickened ridges along the dorsal margins of the dental 

plates (pi. 4, fig. 2a; pi. 6, fig. Ic). The anterior termination of a tooth is marked by a notch in the edge of the 

dental plate. In some well-preserved specimens, a short 

spine projects anteriad from the notch. The dorsal edges 

of the teeth are depressed only slightly below an imaginary extension of the plane of the interarea, perhaps 

because the dorsal valve of Tetraphalerella generally 

lacks a prominent posterio-lateral socket ridge. In 

gerontic specimens, especially of stratigraphically 

younger species such as T. neglecta (James) and T.

cooperi Wang, the teeth are somewhat thicker. Additionally, the notch between the lateral edge of a tooth 

and the anterior edge of the palintrope may be filled 

with secondary shell matter to produce a tooth much like 

that of Rafinesquina. Commonly, the delicate teeth of 

immature specimens are missing because of fracture, 

and in gerontic specimens, the teeth may be dulled or 

obscured by deposits of secondary shell matter on their 

lateral and medial surfaces. The teeth of Tetraphalerella 

do not seem to be semidenticulate.

How these delicate teeth of Tetraphalerella afforded 

adequate articulatory contact or strength is difficult to 

understand, especially for large specimens of some 

species which may be as much as 6V2 cm wide and highly 

domed. Additionally, the delicacy of the tooth contrasts 

with the socket structure, which, although short, is 

generally stoutly constructed.

The teeth of Tetraphalerella are commonly difficult to 

discern in conventionally oriented photographs of the 

ventral interior, because the teeth may be almost as narrow as the dental plates and thus "lost" along the upper 

(dorsal) edges of the plates (contrast pi. 4, figs. 2a, d, 4d, 

e).

The teeth of Strophomena planumbona tend to be 

blocky, blunt, and wide in comparison with length. Their 

dorsal surfaces are depressed below the plane of the interarea and separated from the interarea by a 

transverse groove or a pocket to accommodate the 

posterio-lateral socket ridge. Well-preserved specimens 

bear many erratically shaped semidenticles. The dental 

plates of Strophomena recede, whereas those of 

Tetraphalerella, except for bearing a notch below the 

anterior termination of the tooth, blend into the muscle 

bounding ridge and thus seem to advance, as noted by 

Wang (1949, p. 29). The dental plates of Tetraphalerella 

tend to be somewhat thinner than those of 

Strophomena, but the dental plates of gerontic 

specimens of both genera are usually obscured by secondary deposits. Both genera may have a fold along the 

length of the dental plate to the apex of the delthyrial 

chamber (pi. 4, fig. 2d). This seems to mark the lateral 

margin of the adjuster muscle scar.

The muscle bounding ridges of both genera are so 

variable that generalization is difficult. The muscle 

bounding ridge of Strophomena tends to rise erectly 

from the floor of the valve, to be rather low, continuous, 

and wide (thick). The muscle bounding ridge of 

Tetraphalerella commonly seems to be pressed down 

against the surface of the valve; that is, the dorsal surface of the muscle bounding ridge lies at a low angle to 

the surface of the valve (pi. 7, figs. 3, 4, 6). The continuity of the muscle bounding ridge around the anterior 

margin of the diductor muscle field and the strength of 

the medial ridge of the diductor muscle field are incon-
L22 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

sistent, ontogenetically related characteristics. The ventral palintrope of both Strophomena and Tetraphalerella 

may be supported by a ridge, especially in gerontic individuals. This is a widespread strophomenacean 

characteristic, not peculiar to Tetraphalerella, as Wang 

(1949, p. 29) indicated.

Inside the dorsal valve, the cardinal-process lobes of 

Tetraphalerella are erect and have large, deeply cupped 

myophores facing posteriad (pi. 4, fig. 16; pi. 7, fig. 86). 

The cardinal-process lobes of Strophomena are lower, 

not so deeply cupped (except in some gerontic 

specimens) and have myophores that face more in the 

ventral direction than toward the posterior. The socket 

structures and chilidia of these genera are not strikingly 

different. The sockets of Tetraphalerella do not bear 

semidenticles, whereas the edges of the sockets of 

Strophomena may be prominently semidenticulate. 

Tetraphalerella has an inconspicuous medial ridge extending anteriad from the notothyrial platform (pi. 4, 

figs. 16, 56; Wang, 1949, pi. 8, fig. 4). Otherwise, transmuscle ridges in the dorsal valve are faint to absent. In 

Strophomena, juvenile specimens bear grooves where 

ridges will develop. Adult and gerontic specimens 

possess elaborate ridges, including a breviseptum, 

trans-muscle ridges and, in some species, adventitious 

ridges.

Finally, perhaps the most apparent difference between these genera is found in the pseudopuncta. The 

pseudopuncta of Tetraphalerella are coarse and widely 

spaced compared with those of Strophomena. Pope 

(1976, p. 206) has shown that Strophomena has about 

three times as many pseudopuncta per unit area of shell 

as has Tetraphalerella and that the diameter of the 

taleolae of Strophomena is about half the diameter of the 

taleolae of Tetraphalerella. Additionally, as Wang 

(1949, pi. 8, fig. 6) clearly showed, the pseudopuncta of 

Tetraphalerella are arranged in radial rows, whereas 

they are randomly distributed in Strophomena. Care 

must be exercised in observing the pseudopuncta. 

Either exfoliated or etched surfaces of the shell should 

be examined because interior surfaces of Strophomena 

may possess widely spaced endospines that do not truly 

reflect the densely packed pseudopuncta below the surface.

In summary, Tetraphalerella and Strophomena externally are homeomorphic. Their differences are of about 

the same nature and degree as those that separate 

Rafinesquina and Oepikina.

Another problem that cannot be solved at this time 

concerns the genus Tetraphalerella. In 1933, Bancroft 

erected the genus Longvillia based upon Orthis grandis 

J. de C Sowerby. Salmon (1942, p. 573) misdirected 

understanding of Longvillia (and misspelled the name, 

Longvilleia) by suggesting that some species of Rafinesquina of Cincinnatian age might belong to Longvillia. 

Williams (1963, p. 452) assigned Orthis grandis Sowerby to Strophomena, and in 1965 (p. H384) he placed 

Longvillia in synonymy with Strophomena.

Excellent molds attributed to Strophomena grandis 

from the "Wattsella unguis zone" of the Horderley 

District, East Shropshire, England, are in the collections of the U.S. National Museum (Natural History) 

under accession number 105890. Latex casts from these 

specimens conform in all major morphological features 

to Tetraphalerella. Rather coarse, crudely aligned 

papillae on the internal surfaces of the valves suggest 

the presence of coarse large pseudopuncta. If the shell 

matter of Strophomena grandis could be found and if 

this species is coarsely pseudopunctate, then 

Tetraphalerella must be regarded as a junior subjective 

synonym of Longvillia Bancroft, 1933, type species by 

original designation, Orthis grandis Sowerby.

Tetraphalerella cf. T. costellata (Cooper)

Plate 4, figures 2-6; plate 6, figures 1-2

1956. Strophomena costellata Cooper, Smithsonian Misc. Colln., v. 

127, pts. 1-2, p. 933-934, pi. 255, A, figs. 1-19.

Diagnosis. - Shells small; outline semicircular, widest 

at hingeline, slightly alate; convexity low. Posterior 

region of dorsal valve with a shallow short sulcus; 

posterior region of ventral valve with a low short fold. 

Pseudodeltidium arched, slightly carinate. Parvicostellae very fine, very uniform.

Description. - Shells small. Outline semicircular to 

slightly subrectangular or subtriangular; slightly alate, 

greatest width at hingeline. Anterior margin uniformly 

rounded; lateral margins slightly convergent; posterior 

margin pointed (pi. 4, figs. 3c, 46). Convexity low, 

posterior regions of both valves almost planate, greatest 

curvature near anterior margin. Posterior region of dorsal valve with a short shallow sulcus; posterior region of 

ventral valve with a short low fold (pi. 4, fig. 3). Dorsal 

interarea short; ventral interarea long, set at a sharply 

acute angle to external surface. Cardinal extremities 

bent in dorsal direction (pi. 4, fig. 3d). Pseudodeltidium 

long, narrow, subcarinate (pi. 4, figs. 2a, 3d). Foramen 

minute, round, apical.

Parvicostellae very fine, numbering 26 to 34 per 5 

mm; uniform in height or regularly alternating (pi. 4, 

figs. 4/, 5c). Varices very fine, sharply delineated.

Teeth very narrow, located on dorsal edge of dental 

plates (pi. 4, figs. 2a 4d; pi. 6, fig. Ic). Dental plates 

merge into low inclined muscle-bounding ridges (pi. 4, 

figs. 26, 4e). Dental plates slightly folded, fold extending 

to apex of delthyrial cavity (pi. 4, figs. 2a-d, kd-e). 

Anterior margin of diductor muscle scar obscure. Interior of dorsal valve smooth, lacking prominent ridges
SILIC1FIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L23

or septa (pi. 4, fig. 56). Small sharp endospines in ventral 

valve, aligned radially in paired rows.

Remarks. -This species is distinguished from all other 

species of Tetraphalerella (and Strophomena) by its low 

convexity, knife-sharp posterior edge on ventral valve, 

pointed posterior margin, low sulcus in the dorsal umbo 

and fold in the ventral umbo and by its exceedingly fine 

uniform costellae. Additionally, the rows of endospines 

are paired, a feature not observed in all species of 

Tetraphalerella.

These specimens from Kentucky are probably 

juvenile, which accounts for the incomplete musclebounding ridges, (compare pi. 4, fig. 4d, with Cooper, 

1956, pi. 255, fig. 11), obscure muscle scars, and thin 

dental plates. The lateral-anterior edges of the valves, 

which in topotypic specimens of T. costellata from the 

Bromide Formation of Oklahoma are ventrally flexed, 

are chipped, causing the valves to appear more subtriangular in shape than they may have been originally 

(pi. 4, figs. 3, 4). Finally, these specimens from Kentucky have a greater number of costellae per 5 mm 

along the anterior margin (26-34) than have topotypic 

specimens of T. costellata (Cooper), which have 17-20 

costellae per 5 mm.

T. cf. T. costellata resembles Strophomena platyumbonata Cooper (1956, pi. 254, C) from the Carters 

Limestone of Alabama in ornament and outline. S. 

platyumbonata, however, is conspicuously alate and has 

a rather narrow diductor muscle field. S. platyumbonata 

is a reasonable alternative identification for these 

specimens from Kentucky.

Measurements. -Largest ventral valve, 18 mm wide x 

15 mm long. Other ventral valves, 14 mm wide x 11 mm 

long; 13V4 mm wide; x 11 mm long.

Specimens and occurrence. - All studied specimens are 

composed of fine-grained dense silica. They include 5 

ventral valves, 1 incomplete dorsal valve, 1 fine articulated specimen, and several fragments. Specimens 

are from USGS loc. 5078-CO, Camp Nelson Limestone 

near High Bridge, Ky. Figured specimens are numbered 

USNM 245320-245326. Fragments resembling T. cf. T. 

costellata occur unsilicified in limestone recollected (by 

Miami University) from 7875-CO, Camp Nelson 

Limestone near High Bridge, Ky.

Tetraphalerella cf. T. musculosa (Fenton)

Plate 7, figures 1-9

1928. Strophomenamusculosa Fenton, Am. Midland Naturalist, v. 11,

nos. 3, 4, p. 153-154, pi. 8, figs. 1-7. 

1956. S. musculosa Cooper, Smithsonian Misc. Colln., v. 127, pt. 1, p.

942.

Diagnosis. -Shells large; outline semicircular, subrectangular, or subtriangular, obscurely nasute; alate. Dorsal valve strongly convex. Parvicostellate, alternation

irregular. Cardinal extremities deeply and coarsely 

rugose. Diductor muscle field wide, flabellate, radially 

ridged; muscle-bounding ridge scalloped. Cardinalia 

small relative to size of valve.

Description. -Valves large; outline long and subrectangular in small specimens to subrectangular, subtriangular, or transversely semicircular in large 

specimens (pi. 7, figs. 2, 3, 9a). Cardinal extremities 

slightly rounded to alate (pi. 7, fig. 5; Fenton, 1928, pi. 8, 

fig. 1), and dorsally flexed (pi. 7, fig. 96). Anterior 

margin slightly nasute (pi. 7, figs. 3, 9a). Valves strongly 

convexo-concave; umbos planate, greatest curvature 

just behind midvalve. Ventral interarea long, flat; dorsal 

interarea very short; pseudodeltidium arched and slightly carinate (pi. 7, fig. 4).

Parvicostellae coarse, irregularly alternating, with 

2-4 small costellae between larger costellae. Costellae 

number 11 per 5 mm at anterior margin of dorsal valve. 

Cardinal extremities of dorsal valve deeply rugose (pi. 7, 

fig. 1, left side; Fenton, 1928, pi. 8 , figs. 6-7); posterior 

margin of ventral valve weakly rugose.

Teeth narrow ridges along dorsal edges of dental 

plates (pi. 7, figs. 4, 7). Dental plates laterally flared, 

merge into muscle-bounding ridges. Diductor muscle 

scar large, broadly flabellate, radially ridged (pi. 7, figs. 

3, 4, 7). Muscle-bounding ridge weak (pi. 7, fig. 5) to high 

and thick (pi. 7, figs. 3, 4), with anterior-medial 

emargination. Outer edge of muscle-bounding ridge 

scalloped (Fenton, 1928, pi. 8, figs. 1, 2). Adductor muscle scar oval, slightly elevated (pi. 7, fig. 3). Marginal rim 

of ventral valve deeply grooved (Fenton, 1928, pi. 8, fig. 

1). Cardinalia small relative to size of valve. Cardinal 

process lobes tall, erect, deeply cupped (pi. 7, fig. 86); 

socket buttress ridges delicate, low, recurved (pi. 7, fig. 

8a; Fenton, 1928, pi. 8, fig. 5). Medial ridge low, broad; 

trans-muscle septa obscure (Fenton, 1928, pi. 8, fig. 5). 

Endospines coarse, radially arranged in paired rows.

Remarks.-These specimens are poorly preserved in 

friable saccharoidal silica, beekite (chalcedony), or 

fragile, dense silica with crystalline overgrowths. The 

thin margins of these shells and fine surface details are 

largely lacking, so the descriptions of costellae and 

outline shape are tentative. Referral of these specimens 

to T. musculosa is provisional but is the most appropriate assignment, considering the large size and 

considerable inflation of the valves, the large diductor 

muscle field, and the deeply wrinkled cardinal extremities of the largest dorsal valve.

Measurements and occurrence.-Total sample, 17 

specimens, most incomplete. The largest dorsal valve 

measures 36 mm wide x 30V2 mm long x 14% mm high; 

a smaller dorsal valve measures 28 mm wide x 23 mm 

long. The largest ventral valve measures 33 mm wide x 

approximately 29 mm long. Other ventral valves are: 34
L24 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

mm wide x 29 mm long; 22V2 mm wide x 19V2 mm long; 

and 18V2 mm wide x 16 mm long. Judging from the size 

of the muscle-bounding ridge of incomplete specimens, 

the maximum size should exceed the largest measured 

ventral valve by about 18 percent; that is, it should be 

about 44 mm wide.

Figured specimens are from USGS loc. 7784-CO, 

Curdsville Limestone Member, Lexington Limestone, 

near the crossing of U.S. Route 27 and the Kentucky 

River. Other fragmentary specimens are from Iocs. 

5083-CO, Curdsville Limestone Member of Lexington 

Limestone, near Blackburn Memorial Bridge on U.S. 

Route 62 over the Kentucky River; 7782-CO, same 

general location; and 7785-CO, Curdsville Limestone 

Member of Lexington Limestone, near U.S. Route 27 

bridge over the Kentucky River.

Tetraphalerella sp.

Plate 4, figure 1

Description. - Shell medium size; outline semicircular. 

Profile strongly convex, somewhat geniculate; almost 

planate in posterior third of valve, greatest curvature 

near midvalve. Ornament finely parvicostellate, distinctly alternate. Cardinalia strong; medial ridge narrow and low; trans-muscle septa obscure.

Discussion.-A unique complete dorsal valve unquestionably belonging to Tetraphalerella was found among 

specimens of T. cf. T. costellata and Furcitella cf. F. 

scofieldi from USGS loc. 5078-CO. This specimen is 

larger, more convex, and has more strongly alternating 

ornament than do T. costellata or T. platyumbonata 

(Cooper). The valve most closely resembles T. auburnensis nasuta (Cooper), which Cooper (1956, p. 106) 

reported from the Tyrone Limestone of Kentucky. The 

valve, however, is more convex than T. auburnensis 

nasuta and is not nasute. The valve is smaller, more 

finely costellate, and has relatively stronger cardinalia 

than does T. musculosa.

Measurements.-2l v/2 mm wide, 16% mm long, 6V2 

mm high. Costellae number 17-20 per 5 mm along 

anterior margin, with 2-4 smaller costellae per bundle.

Occurrence.-One complete, densely silicified dorsal 

valve from USGS loc. 5078-CO, Camp Nelson 

Limestone, near High Bridge, Ky. USNM number 

245319. Another coarsely silicified, incomplete, and 

unidentifiable specimen assigned to Tetraphalerella 

comes from USGS loc. 4964-CO, Grier Limestone 

Member, Lexington Limestone, near Frankfort, Ky.

Family LEPTAENIDAE Hall and Clarke, 1894 

Subfamily LEPTAENINAE Hall and Clarke, 1894

Genus LEPTAENA Dalman, 1828

1828. Leptaena Dalman, Svenska Vetensk. Akad. Handl., 1827, p. 93. 

1957. Leptaena, Spjeldnaes, Norsk Geol. Tidsskrift, v. 37, p. 171-174.

1967. Leptaena, Kelly, Palaeontology, v. 10, pt. 4, p. 590-594.

1968. Leptaena, Cocks, British Mus. (Nat. History) Bull., v. 15, no. 6, 

p. 299-302.

Type species. -Leptaena rugosa Dalman, 1828; subsequent designation of King, 1846, p. 28.

Diagnosis. - Shells transversely subrectangular to 

semielliptical; cardinal angles acute to alate. Profile 

with sharp dorsal geniculation; generally with narrow 

ridge on ventral valve along line of geniculation. 

Costellae uniform, crossed by prominent concentric 

rugae. Pseudodeltidium reduced; chilidium prominent; 

foramen open. Pseudopuncta coarse. Teeth strong, 

blunt; dental plates receding. Diductor muscle scar oval, 

impressed, with low muscle-bounding ridge. Cardinal 

process lobes tabulate. Notothyrial platform anchorshaped; medial ridge low, breviseptum narrow; transmuscle ridges obscure.

Remarks. -The synonymy of Leptaena shown above is 

necessarily abbreviated. It cites only the original 

description of this well-known genus, plus three contemporary studies in which additional information and 

references may be obtained.

Leptaena kentuckiana, n. sp.

Plate 8, figures 1-5

Diagnosis. -Large, thin-shelled leptaenid with free 

margin uniformly rounded. Cardinal angles orthogonal 

to alate. Geniculation at about 15 mm from beak, not 

preceded by a prominent depression or ridge. Costellae 

coarse and wavering; rugae discontinuous, moderate in 

number and height. Diductor muscle scar not bordered 

by a ridge.

Description. -Valves large, thin shelled. Outline 

transversely semielliptical, with slight truncation along 

anterio-central margin (pi. 8, fig. 4a). Cardinal extremities orthogonal (pi. 8, fig. 4a) to slightly alate. Ventral umbonal region gently convex (pi. 8, figs. 2a, 4c); 

central region of valve flat, undulating. Geniculation of 

ventral valve at 15 mm from beak, not preceded by 

prominent depression or ridge. Dorsal valve planate 

from beak to geniculation. Trail short, nonrugose, very 

thin; set at 55° to surface of valve. Hingeline gently 

curved in posterior view.

Costellae of disc coarse, wavering; separated by deep 

interspaces (pi. 8, fig. 16). Costellae of variable width, 

widest at crests of rugae (pi. 8, fig. 36), increasing in 

width toward margin of valve. Costellae number about 9 

per 5 mm in the lateral sectors of the valve, 10-14 per 5 

mm in the anterio-central region. Costellae on trail low, 

fine, uniform in width. Protegular region not costellate 

(pi. 8, fig. 36). Intercalation of costellae more common 

than bifurcation. Rugae moderately prominent, discontinuous, numbering 3-5 per 5 mm toward margin of disc.
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L25

Umbonal regions obscurely rugose. Valves irregularly 

deformed, possessing growth interruptions.

Interareas long, flat, striated (pi. 8, figs. Ic, 4e). 

Pseudodeltidium short, highly arched (pi. 8, figs. 2c, d). 

Foramen round, mesothyrid.

Teeth large, blunt; dental plates receding, laterally 

flared (pi. 8, figs. 4<2, e). Diductor muscle scar oval, impressed into shell, not surrounded by ridge (pi. 8, figs. 

4d, 4e). Adductor muscle scar and track narrow (pi. 8, 

fig. 4c£). Narrow adjuster muscle scar at base of dental 

plates. Interior of ventral valve corrugated by rugae, 

striated by costella,e (pi. 8, figs. Ic, 46). Endospines 

coarse and regularly positioned (pi. 8, figs. 3c, e).

Ontogeny.-The smaller figured specimens of L. kentuckiana are assumed to be juveniles of the single large 

ventral valve, the holotype; they are from the same collection. If this is true, the species shows some ontogenetic change in outline shape, profile, ornament, 

and diductor muscle scar. The outline shape of the 

juvenile valves is more transverse and alate (pi. 8, figs. 

16-36) than that of the adult valve. The convexity of the 

juvenile ventral valves is greater (pi. 8, figs. 16, 2a) than 

that of the disc of the adult valve. Costellae increase in 

width to the margin of the juvenile valves, whereas this 

trend is reversed in the anterio-central region and on 

the trail of the adult valve. Rugae are more prominent 

on the adult valve. Juvenile ventral valves show only a 

faint outline of the diductor muscle scar which in the 

adult shell is deeply impressed.

The dorsal valve of L. kentuckiana is known only from 

juvenile specimens. The juvenile dorsal valve is broadly 

transverse, alate, and planate to slightly concave (pi. 8, 

figs. 36-c, 5a-6). Rugae are weaker but more continuous than those of the ventral valve. The cardinal 

process lobes are divergent vertical blades; the sockets 

are short and shallow (pi. 8, figs. 3c-e), The chilidium is 

folded into the cleft between the cardinal process lobes 

(pi. 8, fig. 3e).

Comparison of species.-L. kentuckiana is distinct 

from all other known species of Leptaena from the Ordovician of North America by the combination of its size, 

shape, beak-to-genioulation distance, and ornament. L. 

kentuckiana most closely resembles L. ordovicica 

Cooper and L. richmondensis precursor Foerste. L. ordovicica, figured by Cooper (1956, pis. 208, 212, 228), 

has discontinuous rugae and, in some specimens from 

Linville Station, Va., has oval diductor muscle scars that 

lack bounding ridges. L. ordovicica, however, differs 

from L. kentuckiana by being smaller, more transverse 

in outline, more finely costellate, and by being much 

shorter from the beak to the initiation of geniculation. 

Additionally, many specimens of L. ordovicica have a 

prominently elevated rim posterior to the geniculation. 

L. richmondensis precursor Foerste resembles L. kentuckiana in possessing somewhat discontinuous low 

rugae and in lacking a depression or rim bordering the 

geniculation. L. richmondensis precursor, however, is 

rather small, possesses a long trail, and initiates 

geniculation at about 8 mm anterior to the beak.

Leptaena richmondensis richmondensis Foerste differs from L. kentuckiana by having much stronger and 

more continuous rugae, a longer trail bordered by a rim, 

generally a slight anterior emargination and alation of 

the cardinal extremities, and a shorter beak-togeniculation distance. L. tenuistriata(!) Sowerby, as 

figured by Foerste (1910, p. 45-46, pi. 5, fig. 9a-6), is 

smaller and more transverse than L. kentuckiana and 

does not bear as many rugae. Both L. gibbosa (James) 

and L. gibbosa invenusta Foerste are too finely 

costellate and too faintly rugose to be conspecific with 

L. kentuckiana. L. moniquensis Foerste (1924, p. 

116-117, pi. 14, figs. 2-3) has distinctly alternate ornament. L. kentuckiana cannot be identified as L. 

reticulata (Shaler), figured by Twenhofel (1927, pi. 22, 

fig. 19), because the rugae of the latter species are too 

numerous and anastomosing, and its geniculation is 

poorly defined.

Among Ordovician species of Leptaena described or 

redefined in western Europe, L. kentuckiana bears 

greatest resemblance to L. salopiensis Williams (1963) 

from the Actonian Stage of the Bala District, 

Merionethshire, Wales. This European species, 

however, is slightly larger and more transverse than L. 

kentuckiana yet has a shorter beak-to-geniculation 

dimension. Additionally, the diductor muscle scar of L. 

salopiensis is bordered by a modest ridge. L. rugosa 

Dalman, type species, differs conspicuously from!/, kentuckiana by the possesion of strong continuous rugae, a 

high rim marginal to the geniculation, and a long trail.

L. kentuckiana is not assigned to the genus 

Kiaeromena Spjeldnaes because of its abrupt geniculation, closely spaced rugae, and distinctly leptaenid 

juvenile dorsal valve.

Measurements. -USNM 245367, adult ventral valve: 

length 16.6 mm; width 23.5 mm; distance from beak to 

initiation of geniculation, 15.3 mm; approximate 

greatest height above plane of commissure, 4 mm.

Occurrence, specimens, and types. -USGS loc. 

5136-CO, Upper Ordovician, Reba Member, Ashlock 

Formation, Clara Wilham quarry, Dunnville, Ky. The 

collection contains 10 specimens, consisting of 1 adult 

ventral valve and 9 juveniles. The juvenile specimens include two well-preserved ventral valves and two wellpreserved dorsal valves; the others are poorly preserved 

or fragmentary. The adult ventral valve shown on pi. 8, 

fig. 4, is designated the holotype; it is USNM 245367. 

The four well-preserved juvenile valves shown on pi. 8,
L26 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

figs. 1-3, 5, are assigned USNM numbers 245363 to 

245366.

Subfamily MURINELLINAE Pope, 1976 

Genus MURINELLA Cooper, 1956

1956. Murinella Cooper, Smithsonian Misc. Colln., v. 127, p. 844-845.

Type species.-Murinella partita Cooper, 1956, p. 

847-848, original designation.

Diagnosis.- Outline subrectangular to semielliptical; 

profile biconvex to weakly concavo-convex. Parvicostellate, with major growth interruptions or comae 

common. Pseudodeltidium large, arched; foramen open. 

Teeth strong, blunt; dental plates short, widely flared, 

not advancing. Diductor muscle field oval, divided by 

medial ridge; muscle-bounding ridge low. Cardinal process lobes short, stout; myophores cupped. Socket buttress ridges thick. Dorsal medial ridge short, broad; 

trans-muscle ridges short, strongly bent; breviseptum 

long. Interior of dorsal valve with prominent marginal 

flange.

Murinella? sp.

Plate 5, figure 7

Description. - Known from one, incomplete, coarsely 

silicified dorsal valve. Valve subrectangular, wider than 

long, with rounded cardinal angles. Profile of valve 

gently sigmoidal; convex toward posterior, planate in 

central region, concave toward anterior, with a reflexed 

and thickened marginal rim. Radial ornament obscure. 

Chilidium poorly preserved; continuous around 

posterior ends of cardinal process lobes; merges into 

thin sharp ridge marginal to socket.

Cardinal process lobes stout, low, wider than long; 

myophores cupped, facing toward posterior, wider than 

shafts. Meso-cardinal ridge thin; posterior edge fused to 

chilidium. Sockets shallow; socket buttress ridges widely divergent and thick. Posterior margin of socket defined by an accessory ridge. Medial ridge wide, low, 

short, and unbranched; flanked by two pairs of indistinct 

low broad ridges or swellings in the adductor-musclefield region. Concentric rim thick, relatively high; corresponds to the reflexed margin of exterior, producing 

greatly thickened anterior and lateral margin on valve.

Discussion and comparison.-Unfortunately, this 

curiously shaped brachiopod is known from only one incomplete coarsely silicified valve. The silicification consists of rather coarse, weakly joined, "beekite" beads, 

which have not preserved details of external ornament, 

the internal surface texture of the valve, or, if originally 

present, the thin anterior and lateral margins of the 

valve.

The specimen was part of a collection that contained 

many incomplete valves and fragments of Oepikina 

minnesotensis (Winchell). Although about the same size

as the specimens of Oepikina and as coarsely silicified, 

Murinella! sp. is readily distinguished from Oepikina by 

its plan-shape profile, the external ridge around the 

anterior margin, the large, wide, but short cardinalprocess lobes and the long, widely divergent socket buttress ridges. The specimen superficially resembles 

Oepikina lirata Cooper in plan shape but is readily 

separated from that species by the above-mentioned 

features.

The general shape of this brachiopod superficially suggests relationship to species of Hesperinia, Dactylogonia, Cyphomena, Bellimurina, and Limbimurina 

(minus the trail). Relationship to all these genera is 

doubtful because of the larger cardinal-process lobes and 

the longer recurved socket buttress ridges of this 

specimen. Additionally, this specimen lacks the prominent paired lateral septa possessed by Dactylogonia and 

Cyphomena, the acute cardinal angles of Cyphomena, 

the distinctive ornament of Bellimurina and Limbimurina, and the elaborate trail of Limbimurina; also 

it is considerably younger than Hesperinia.

The most prominent and unusual feature of this 

specimen, its marginal rim, as well as other structures, 

suggests relationship to Murinella Cooper, especially to 

Murinella muralis Cooper (1956, p. 846-847, pi. 226, D, 

figs. 10-28). The specimen from Kentucky compares 

favorably in shape with the specimen of M. muralis 

shown by Cooper (1956) on his plate 226, fig. 25, and in 

size with the specimens shown in his figures 14, 15, 21, 

and 22. The socket buttress ridges resemble those 

shown in Cooper's figure 19, and the cardinal-process 

lobes and wide medial ridge resemble those borne by the 

specimens of his figures 27 and 23. Murinella muralis 

has somewhat more pronounced paired lateral septa 

than does this specimen and a much higher marginal 

rim. The presence of a marginal rim at all on the new 

specimen is cause for suspecting a relationship with 

Murinella. Moreover, Murinella muralis from the 

Wardell Formation of Cooper and Pronty (1943) of Tennessee is compatible in age with this specimen from the 

Camp Nelson Limestone of Kentucky.

Measurements. -Measurements have been taken from 

accurately calibrated photographs because the specimen 

is too delicate to withstand calipers. Length, 11.7 mm; 

width, 16 mm; greatest thickness, at anterior margin, 

2.8 mm.

Occurrence. -USGS loc. 7875-CO, Camp Nelson 

Limestone; High Bridge, Ky. USNM 245337.

Superfamily DAVIDSONIACEA King, 1850

Family FARDENIIDAE Williams, 1965 

(nom. transl. Cooper and Grant, 1974, p. 256)

Genus PIONOMENA Cooper, 1956

1956. Pivnomena Cooper, Smithsonian Misc. Colln., v. 127, pt. 1, p. 

901.
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L27

Type species. -Pionomena neumani Cooper, 1956, p. 

901, 902-903, original designation.

Diagnosis. - Shells small, semicircular, unequally biconvex; cardinal extremities orthogonal to rounded. Ornament multicostellate to weakly fascicostellate. 

Pseudodeltidium short, arched; foramen open, small, 

apical; chilidium complete to bilobed. Impunctate. Teeth 

moderately strong, pointed; dental plates short to slightly advancing. Cardinal process lobes minute, beadlike, 

closely spaced. Dentifers triangular, fixed to valve along 

posterior margin, not fused to floor of valve. Notothyrial 

platform obscure; medial ridge broad, very low.

Remarks.-Cooper (1956), Williams (1965), and Pope 

(1976) assigned Pionomena to the Superfamily 

Strophomenacea. The presence of perideltidial areas on 

P. recens, as well as the impunctate shell matter and 

shape of the cardinalia, require reassignment of 

Pionomena to the Davidsoniacea. The triangular suspended dentifers of Pionomena resemble those of 

Gacella Williams. In contrast, the sockets of Fardenia 

Lament and Coolinia Bancroft are excavated into the 

shell and are bordered by a rodlike brachiophore. 

Pionomena is retained here provisionally within the 

Fardeniidae pending comprehensive restudy of the 

early davidsoniaceans. The structure of the socket may 

provide a means for subdividing the family.

Pionomena recens Neuman, 1967

Plate 7, figures 16-31; text-figure 12

1967. Pionomena recens Neuman, U.S. Geol. Survey, Prof. Paper 

583-A, p. A12-A13, pi. 2, figs. 21-36.

Diagnosis.- Multicostellate. Pseudodeltidium uniformly arched, not carinate. Ventral valve smoothly convex, not folded. Dental plates short; diductor muscle 

scar not bordered by long thin plates.

Morphological addendum and remarks.-The detailed 

description of this species by Neuman (1967, p. 

A12-A13) does not need to be restated here. Some additional morphological attributes of P. recens, however, 

need to be described and considered.

Some specimens of P. recens possess a faint but unmistakable perideltidial area (pi. 7, figs. 206 (scanning 

electron microscope (SEM) photograph), 20c, 216, 226, 

266; Neuman, 1967, pi. 2, fig. 28). Strangely, not every 

ventral valve bears a distinct perideltidium, the ratio 

being about one valve in six that does so.

The perideltidium consists of a triangular region on 

each side of the ventral interarea immediately lateral to 

the pseudodeltidium or lateral to the trace of the tooth 

along the margin of the pseudodeltidium. The surface of 

the perideltidium of P. recens is elevated above the surface of the interarea and is flatter than the surface of the 

interarea, which is gently curved along an axis parallel 

to the hingeline. The thin sheet of shell material that

forms the perideltidium seems, after SEM observation, 

to have originally extended from the lateral margin of 

the pseudodeltidium. On some specimens, subsequent 

erosion or nonpreservation has permitted the trace of 

the tooth adjacent to the pseudodeltidium to show 

through the perideltidium (pi. 7, fig. 20c, left side of 

photograph). The surface of the perideltidium bears 

weak striae (pi. 7, fig. 206) approximately parallel to the 

hingeline. These striae are set at a slight angle to striae 

of the interarea and are somewhat more widely spaced 

than are those of the interarea. Transverse striae of the 

perideltidium, thus, have not simply been pressed up 

through the thin perideltidial sheet from the interarea 

beneath. The perideltidia of two specimens bear still 

fainter, more closely spaced, sagittal striae, not illustrated. These are on eroded areas and seem to reflect 

structures below the surface of the perideltidium. Unfortunately, a distinct perideltidium is not evident on the 

interarea of P. neumani, type species of Pionomena, 

shown by Cooper (1956, pi. 265, fig. 8); what appears to 

be a perideltidium is in fact a collapsed section of the interarea.

A small node or rod occurs on some dorsal valves immediately anterior to and below the cleft between the 

cardinal-process lobes (pi. 7, fig. 246, 286, 296, 30, 31). 

This medial node is on only about one out of seven dorsal 

valves studied. The medial node varies considerably in 

form, from a short angular spine to a rounded bead to a 

rod. The medial node of one specimen (pi. 7, fig. 24a, 6) is 

drawn out into a spike that extends almost as far to the 

anterior as the anterior ends of the dentifers. Careful 

examination of the base of this spike in the SEM shows 

that the process is firmly welded into the shell matter, 

confluent with the shell, and has the same surface texture and apparent porosity as the shell; that is, the spike 

is probably not a foreign fossil fragment lodged between 

the cardinal-process lobes.

The medial node is rarely symmetrical with respect to 

the cardinal-process lobes but generally is set slightly to 

the right of the plane of symmetry. This is not surprising 

because asymmetry of the cardinal-process lobes is observed sporadically throughout the Strophomenida. 

Where asymmetry is evident, it is generally the right 

lobe that departs in shape from the norm. This deformation perhaps resulted from some asymmetry of the soft 

tissues in that part of the animal.

The medial node is of unknown function. Although a 

medial node is not found on all species of davidsoniaceans (sensu Williams, 1965), its occurrence is sufficiently widespread, that to find it so infrequently noted 

is surprising. For example, a medial node is present on 

some but not all specimens of Coolinia subplana (Conrad), as shown on plate 7, figures 14-15. It has been 

shown to occur on Tapajotia tapajotensis Dresser (1954,
L28 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

pi. 4, fig. 8); on Iridistrophia umbella (Barrande), by 

Havlicek (1967, p. 194, pi. 41, figs. 11-12); on Derbyia 

deercreekensis and Derbyoides nebrascensis, by Dunbar 

and Condra (1932, pi. 6, fig. 3 and pi. 14, figs. 3-4); and 

on species of Derbyoides, Hypopsia, and Goniarina, by 

Cooper and Grant (1974, pis. 26, 31, 34, 41 and 43). The 

widespread occurrence of this structure suggests that it 

is not an accidental or pathological deformity of the cardinalia. Additionally, the absence of a medial node from 

the Strophomenacea (s.s.) and its occurrence in species 

of the Davidsoniacea and Orthotetidina (sensu Cooper 

and Grant, 1974) supports the concept of the close relationship of the last two groups.

With regard to the description of P. recens by 

Neuman, it must be made clear that the dorsal "cardinal 

apparatus," specifically, the dentifers in the descriptive 

terminology of Cooper and Grant (1974, p. 258), is suspended above the internal surface ("shell floor") of the 

valve. The dentifers are attached to the shell only along 

their posterior margins. The junction beneath the dentifers is smoothed and perhaps reinforced by a fillet of 

secondary shell matter in larger specimens but is rather 

angular in some thin-shelled juveniles. The dentifers of 

P. recens, thus, differ distinctly from the rodlike 

"brachiophores" of Fardenia and Coolinia, which are 

united to the floor of the valve by a thin vertical partition. The cardinalia of two specimens of Coolinia subplana (Conrad) are shown on plate 7, figures 14-15, for 

comparison. The "brachiophores" on the right side of 

each specimen are complete, but the left "brachiophores" of both specimens are broken, revealing the thin 

supporting partition. If this vertical partition were 

rotated approximately 90° so as to bridge the gap between the lower surface of the "brachiophore" and the 

posterior margin of the shell, a structure much like the 

dentifer of Pionomena would be formed.

Pionomena recens does indeed seem to be impunctate. 

Several dozen specimens examined optically and in the 

SEM fail to show pores, papillae, or endospines that 

might indicate the presence of puncta or pseudopuncta. 

My assignment of Pionomena to the Family Rafinesquinidae (Pope, 1976, p. 151) was based upon the 

association of a fragment of shell bearing endospines 

with specimens of P. neumani, an association that now 

is clearly spurious.

Comparison of species. -In addition to the differences 

between P. neumani Cooper and P. recens noted by 

Neuman (1967, p. A13) there are differences in the form 

of the pseudodeltidia and dental plates of these species.

The pseudodeltidium of P. recens is smoothly arched, 

whereas that of P. neumani is longer, narrower, and 

somewhat carinate along its midline. The dental plates 

of P. neumani extend somewhat farther to the anterior 

than those of P. recens, which although hidden beneath 

the teeth, cannot be described as receding or obsolescent, contrary to the diagnosis by Williams (1965, p. 

H388).

Specimens attributed to Strophomena billingsi Winchell and Schuchert and S. emaciata Winchell and 

Schuchert (nos. 6-6196, 6-6272, and 6116 in the collections of the University of Iowa, both species from the 

Decorah Shale of Iowa) bear a resemblance to P. recens. 

Both species from Iowa possess unmistakable perideltidial areas and seem to lack pseudopuncta. Both 

species may be referred provisionally to Pionomena, but 

this assignment cannot be determined with certainty until suitable internal views are available.

Measurements, specimens, and occurrence. — Figure 12 

is only an approximation of the length-width relationship of the dorsal valves of P. recens. The collections 

contain so few complete and unbroken valves, that 

valves having ragged margins that could be completed 

with reasonable assurance by a thin line also were 

measured. Valves missing a cardinal extremity were 

measured from one lateral extremity to the midline, and 

the total width was obtained by doubling the number.

Numbers of complete specimens and identifiable 

fragments are as follows:

USGS loc.

4879-CO

4880-CO

5015-CO

5016-CO

Ventral valves

1

14

87

1

Dorsal valves

1

23

189

2

Articulated valves

0o26

0

The larger number of dorsal valves present in these 

collections does not indicate current sorting because 

many minute specimens are included. Rather, the 

smaller number of ventral valves reflects their very 

fragile character. Apparently the valves were easily disarticulated; most of the articulated specimens show 

some displacement of the valves.

Specimens illustrated herein bear USNM numbers 

245347 to 245362.

USGS Iocs. 4879-CO and 4880-CO are in the Grier 

Limestone Member of the Lexington Limestone, 

Jessamine County, Ky. Locs. 5015-CO and 5016-CO are 

in the Salvisa Bed, Perryville Limestone Member, Lexington Limestone, near Perryville, Ky.
SILICIFIED STROPHOMENACEAN BRACHIOPODS FROM THE ORDOVICIAN OF KENTUCKY L29

10

DC

LJJ

LJJ

• • • •

•® 

-» • , •—

• •

• • 

•®

®

®

+ 

•

+ A 

A +

EXPLANATION

• Specimen from 5015-CO

® 2 specimens (from 5015-CO) 

on same point

A Specimen from 4880-CO

+ Neuman's measurements 

(1967, p. A13), maximum 

width

Total number of points = 74

5 10

MAXIMUM WIDTH, IN MILLIMETERS

15

FIGURE 12. - Scattergram of the length vs. maximum width of dorsal valves ofPionomena recens Neuman. The columns and tiers of 

points do not lie along whole-millimeter increments because specimens were measured optically magnified x 4.4375, and these 

data were used to construct the diagram. Points representing some of Neuman's (1967, p. A13) published measurements are high in 

the plexus of points because they are from ventral valves and consequently include the additional length of the ventral beak.

REFERENCES CITED

Alexander, R. R., 1975, Phenotypic lability of the brachiopod Rafinesquina alternata (Ordo'/ician) and its correlation with the sedimentologic regime: Journal of Paleontology, v. 49, no. 4, p. 607-618, 2

pis. 

Bancroft, B. B., 1933, Correlation tables of the stages CostonianOnnian in England and Wales: Gloucestershire, England, Nibley

House, Blakeney, 4 p., 3 charts (private pub.). 

Bretsky, P. W., and Bretsky, S. S., 1975, Phenetic variation in some

middle Ordovician strophomenid brachiopods: Geological Society

of America Memoir 142, p. 3-36, 4 pis. 

Cocks, L. R. M., 1968, Some strophomenacean brachiopods from the

British lower Silurian: British Museum (Natural History) Bulletin,

Geology, v. 15, no. 6, p. 283-324, 14 pis.

Cooper, B. N., and Prouty, C. E., 1943, Stratigraphy of the lower 

Middle Ordovician of Tazewell County, Virginia: Geological Society of America Bulletin, v. 54, no. 6, p. 819-886.

Cooper, G. A., 1956, Chazyan and related brachiopods: Smithsonian 

Miscellaneous Collections, v. 127, pt. 1 (text), p. 1-1024; pt. 2 

(plates), p. 1025-1245, 269 pis.

Cooper, G. A., and Grant, R. E., 1974, Permian brachiopods of West 

Texas, II: Smithsonian Contributions to Paleobiology, No. 15, 793 

p., 191 pis.

Dalman, J. W., 1828, Uppstallning och Beskrivning af de i Sverige 

funne Terebratuliter: Svenska Vetenskaps Akademiens Handlingar, 1827, p. 85-155, pis. 1-6.

Dresser, Hugh, 1954, Notes on some brachiopods from the Itaituba 

Formation (Pennsylvanian) of the Tapajos River, Brazil: Bulletins 

of American Paleontology, v. 35, no. 149, p. 15-68, 8 pis.
L30 CONTRIBUTIONS TO THE ORDOVICIAN PALEONTOLOGY OF KENTUCKY AND NEARBY STATES

Dunbar, C. 0., and Condra, G. E., 1932, Brachiopoda of the Pennsylvanian System in Nebraska: Nebraska Geological Survey, 2d ser.,

Bulletin 5, 377 p., 44 pis. 

Fenton, C. L., 1928, Forms of Strophomena from Black River and

Richmond Formations: American Midland Naturalist, v. 11, nos.

3-4, p. 144-159, pis. 8-10. 

Foerste, A. F., 1910, Preliminary notes on Cincinnatian and Lexington

fossils of Ohio, Indiana, Kentucky, and Tennessee: Denison

University Scientific Laboratories Bulletin, v. 16, p. 17-100, 6 pis. 

——— 1924, Upper Ordovician faunas of Ontario and Quebec: Canada

Geological Survey Memoir 138, 255 p., 46 pis. 

Hall, James, and Clarke, J. M., 1892, An introduction to the study of

the genera of Paleozoic Brachiopoda: New York Geological

Survey, Paleontology, v. 8, pt. 1, 367 p., 20 pis. [1893]. 

Havlicek, Vladimir, 1967, Brachiopoda of the suborder

Strophomenidina in Czechoslovakia: Czechoslovakia Ustredni

Ustav Geologicky Rozpravy, v. 33, 235 p., 52 pis. 

Jaanusson, Valdar, 1971, Evolution of the brachiopod hinge: Smithsonian Contributions to Paleobiology, No. 3, p. 33-46, 2 pis., 6

figs. 

Kelly, F. B., 1967, Silurian leptaenids (Brachiopoda): Palaeontology, v.

10, pt. 4, p. 590-602, pi. 8-9. 

King, William, 1846, Remarks on certain genera belonging to the Class

Palliobranchiata: Annals and Magazine of Natural History, v. 18,

p. 26-42, 83-94. 

Miller, S. A., 1897, Strophomena and the type of the genus: Natural

Science Journal [New Bedford, Mass.], v. 1, no. 2, p. 29-35. 

Neuman, R. B., 1967, Some silicified Middle Ordovician brachiopods

from Kentucky: U.S. Geological Survey Professional Paper

583-A, p. A1-A14, 2 pis. 

Nickles, J. M., 1903, The Richmond Group in Ohio and Indiana and its

subdivisions, with a note on the genus Strophomena and its type:

American Geologist, v. 32, p. 202-218. 

Parsley, R. L., 1981, Echinoderms from Middle and Upper Ordovician

rocks of Kentucky: U.S. Geological Survey Professional Paper

1066-K, 9 p. 

Pojeta, John, Jr., 1979, The Ordovician paleontology of Kentucky and

nearby States-Introduction: U.S. Geological Survey Professional

Paper 1066-A, 48 p.

Pope, J. K., 1976, Comparative morphology and shell histology of the 

Ordovician Strophomenacea (Brachiopoda): Palaeontographica 

Americana, v. 8, no. 49, p. 129-213, 31 figs.

Richards, R. P., and Bambach, R. K., 1975, Population dynamics of 

some Paleozoic brachiopods and their paleoecological significance: 

Journal of Paleontology, v. 49, no. 5, p. 775-798, 19 figs.

Salmon, E. S., 1942, Mohawkian Rafinesquinae: Journal of Paleontology, v. 16, no. 5, p. 564-603, pis. 85-87, 8 figs.; correction, v. 17, 

no. 3, p. 309, 1943.

Spjeldnaes, Nils, 1957, The Middle Ordovician of the Oslo Region, 

Norway; 8. Brachiopods of the Suborder Strophomenida: Norsk 

Geologisk Tidsskrift, v. 37, no. 1, p. 1-214, 14 pis.

Twenhofel, W. H., 1927, Geology of Anticosti Island: Canada Geological Survey Memoir 154, 481 p., 160 pis.

Walker, K. R., and Parker, W. C., 1976, Population structure of a pioneer and a later stage species in an Ordovician ecological succession: Paleobiology, v. 2, no. 3, p. 191-201, 8 figs.

Wang, Yii, 1949, Maquoketa Brachiopoda of Iowa: Geological Society 

of America Memoir 42, 55 p., 12 pis.

Williams, Alwyn, 1962, The Barr and lower Ardmillan series (Caradoc) 

of the Girvan district, south-west Ayrshire, with descriptions of 

the Brachiopoda: Geological Society of London Memoir 3, 267 p., 

25 pis.

——— 1963, The Caradocian brachiopod faunas of the Bala district, 

Merionethshire: British Museum (Natural History) Bulletin, 

Geology, v. 8, no. 7, p. 327-471, 16 pis.

1965, Suborder Strophomenidina, in Williams, Alwyn, and

others, 1965, Brachiopoda, pt. H o/Moore, R. C., ed., Treatise on 

invertebrate paleontology: New York and Lawrence, Kans., 

Geological Society of America and University of Kansas Press, v. 

1, p. H362-H412.

Winchell, N. H., 1881, New Brachiopoda from the Trenton and Hudson 

River Formations in Minnesota: Minnesota Geological and Natural 

History Survey, Annual Report 9 for 1880, p. 115-124.

Winchell, N. H., and Schuchert, Charles, 1892, Preliminary descriptions of new Brachiopoda from the Trenton and Hudson River 

Groups of Minnesota: American Geologist, v. 9, p. 284-294.

——— 1895, The Lower Silurian Brachiopoda of Minnesota: Minnesota Geological and Natural History Survey, Final Report, v. 3, 

pt. 1, p. 333-474, pis. 29-34.
PLATES 1-8

Contact photographs of the plates in this report are available, at cost, from the U.S. Geological 

Survey Library, Federal Center, Denver, CO 80225.
PLATE 1

FIGURES 1-14. Oepikina minnesotensis (Winchell) (p. L6). Exterior of ventral valves. Figs. 1, 3-5 from USGS loc. 7875-CO; figs. 2, 6-14 from 

USGS loc. 5078-CO.

1. Highly inflated specimen, a, Stereophotographs, x 1. 6, x 2. c, Profile, x 2. USNM 245277.

2. Specimen with normal outline and profile, and strongly alternate costellae. Ornament magnified on pi. 2, fig. 12. 

a, Stereophotographs, x 1. 6, x 2. USNM 245291.

3. Elongated specimen, a, x 1. 6, x 2. USNM 245278.

4. Highly inflated specimen, a, x 1. 6, x 2. c, Profile, x 2. USNM 245279.

5. Specimen with moderate curvature, a, Stereophotographs, x 1. 6, x 2. c, Profile, x 2. USNM 245280.

6. Slightly nasute specimen, a, Stereophotographs, x 1. 6, x 2. USNM 245292.

7. Specimen with low profile and sharp uniform costellae. Ornament magnified on pi. 2, fig. 11. a, x 1. 6, x 2. USNM 245293.

8. Sharply geniculate specimen, a, x 1. 6, x 2. USNM 245294.

9. Transverse, sharply geniculate specimen with angular cardinal extremities, a, x 1. 6, x 2. USNM 245295.

10. Rugose specimen, x 2. USNM 245296.

11. Flat specimen with growth interruption and injury, a, x 1. 6, x 2. USNM 245297.

12. Flat specimen with growth interruption, a, x 1. 6, x 2. USNM 245298.

13. Nasute specimen, x 1. USNM 245299.

14. Small flat specimen, a, x 1. 6, x 2. USNM 245300.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L PLATE 1

OEPIKINA
PLATE 2

FIGURES 1-12. Oepikina minnesotensis (Winchell) (p. L6). Interior of ventral valves and ornament. Figs. 1-4, 7-12 from USGS loc. 

5078-CO; figs. 5-6 from USGS loc. 7875-CO.

1. Large, highly inflated specimen, a, Stereophotographs, x 1. b, x 2. c, Ventral structures, x 4. d, Grooved tooth with 

semidenticles, pedicle callist, x 6. USNM 245301.

2. Specimen with normal convexity, a, Stereophotographs, x 1. b, x 2. USNM 245302.

3. Specimen with low convexity, a, x 1. b, x 2. USNM 245303.

4. Abraded specimen with moderate convexity. Hole in beak is caused by lack of preservation of pseudodeltidium. a, x 2. 

b, Grooved teeth and pedicle callist, x 4. c, Stereophotographs, x 1. USNM 245304.

5. Highly inflated, transverse specimens, x 2. USNM 245281.

6. Highly inflated specimen, x 2. USNM 245282.

7. Small specimen, a, x 1. b, x 2. USNM 245305.

8. Small subtriangular specimen, a, x 1. b, x 2. USNM 245306.

9. Specimen with low convexity, a, x 1. b, x 2. USNM 245307.

10. Ornament, dorsal valve. Specimen shown on pi. 3, fig. 19. x 4. USNM 245308.

11. Ornament, ventral valve. Specimen shown on pi. 1, fig. 7. x 4. USNM 245293.

12. Ornament, ventral valve. Specimen shown on pi. 1, fig. 2. x 4. USNM 245291.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L PLATE 2

OEPIKINA
PLATE 3

FIGURES 1-19. Oepikina minnesotensis (Winchell) (p. L6). Interior and exterior of dorsal valves. Figs. 1-8 from USGS loc. 7875-CO; figs. 

9-19 from USGS loc. 5078-CO.

1. Subcircular specimen, x 2. USNM 245283.

2. Large specimen with inclined cardinal process lobes, x 2. USNM 245284.

3. Transverse specimen with deep round adductor muscle scars and short transmuscle ridges, x 2. USNM 245285.

4. Flat specimen, x 2. USNM 245286.

5. Large specimen without prominent marginal rim, x 2. USNM 245287.

6. Deformed subrectangular specimen, x 2. USNM 245288.

7. Subtriangular specimen, x 2. USNM 245289.

8. Specimen with prominent transmuscle ridges, x 2. USNM 245290.

9. Specimen with well-defined cardinalia. a, Stereophotographs, x 2. b, Specimen inclined to show cardinalia. Note semidenticles in sockets and lack of silicification of core of cardinal process lobes, x 4. USNM 245309.

10. Young transverse specimen with weakly defined transmuscle ridges, x 2. USNM 245310.

11. Large specimen with circular marginal rim, x 2. USNM 245311.

12. Small flat deformed specimen. Note pronounced posterior-lateral transmuscle ridges and long socket buttress ridges, x 2. 

USNM 245312.

13. Specimen with well-defined cardinalia. a, x 2. b, Inclined view, x 4. USNM 245313.

14. Small flat specimen showing the early development of the posterior-lateral transmuscle ridges, x 2. USNM 245314.

15. Small flat specimen with radial wrinkles, x 2. USNM 245315.

16. Subtriangular specimen, incomplete, a, x 2. b, Inclined view; note semidenticles in sockets, x 4. USNM 245316.

17. Dorsal exterior, Stereophotographs, x 2. USNM 245317.

18. Dorsal exterior with slight rugation along hingeline, x 2. USNM 245318.

19. Dorsal exterior. Magnified view shown on pi. 2, fig. 10. x 2. USNM 245308.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L PLATE 3

OEPIKINA
PLATE 4

FIGURE 1. Tetraphalerella sp. (p. L20). Stereophotographs, exterior and interior of highly inflated dorsal valve. USGS loc. 5078-CO.

a-b, x 2. USNM 245319. 

FIGURES 2-6. Tetraphalerella cf. T. costellata (Cooper) (p. L22). USGS loc. 5078-CO.

2. Posterior region of a large, incomplete ventral valve, a-d, x 3. USNM 245320.

3. Complete specimen, a, x 1. b, Stereophotographs, dorsal valve, x 2. c, Stereophotographs, ventral valve, x 2. d, Dorsal 

valve inclined to show growth interruption and ventral interarea, x 2. USNM 245321.

4. Exterior and interior of ventral valve, a, x 1. b, Stereophotographs, exterior, x 2. c, Stereophotographs, interior, x 2. d-e, 

Two views of posterior region, x 3. /, Ornament, x 6. USNM 245322.

5. Incomplete dorsal valve, a, Stereophotographs, x 2. b, Interior, x 2. c, Ornament, x 6. USNM 245323.

6. Exterior and interior of juvenile ventral valve, a-b, x 3. USNM 245324.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066—L PLATE 4

TETRAPHALERELLA
PLATE 5

FIGURES 1-6. Furcitetta cf. F. scofieldi (Winchell and Schuchert) (p. L19). USGS loc. 5078-CO.

1. Large incomplete dorsal valve, a-b, Stereophotographs, exterior, interior, x 2. c-e, Cardinalia, x 3. USNM 245327.

2. Small incomplete dorsal valve, a-b, Stereophotographs, x 2. c-d, Cardinalia, x 3. e, Ornament, x 5. USNM 245328.

3. Small complete specimen. Note faint dorsal fold, a, x 1. b, Rotated to show ornament, fold, and interarea, x 3. c-d, 

Stereophotographs, dorsal valve, ventral valve, x 2. USNM 245329.

4. Poorly preserved dorsal valve, a-b, Stereophotographs, exterior, interior, x 2. USNM 245330.

5. Small dorsal valve, a, Exterior, x 2. b, Interior, x 2. c, Ornament, x 5. USNM 245331.

6. Small, poorly preserved dorsal valve, a, Exterior, x 2. b, Interior, x 2. USNM 245332.

FIGURE 7. MurinelM sp. (p. L26). Poorly preserved dorsal valve. USGS loc. 7875-CO. a, Stereophotographs, interior, x 2. b, Exterior, 

x 2. USNM 245337.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L PLATE 5

FURCITELLA AND MURINELLA ?
PLATE 6

FIGURES 1-2. Tetraphalerella cf. T. costellata (Cooper) (p. L22). USGS loc. 5078-CO.

1. Large ventral valve, a-b, Stereophotographs, exterior, interior, x 2. c, Posterior region, x 3. d, Ornament, x 6. USNM 

245325.

2. Small ventral valve, a-b, Exterior, interior, x 2. USNM 245326. 

FIGURES 3-6. Furcitella cf. F. scofieldi (Winchell and Schuchert) (p. L19). USGS loc. 5078-CO.

3. Large ventral valve with faint sulcus and marginal plicae, a-b, Stereophotographs, exterior, interior, x 2. c, Posterior 

region inclined, x 3. d, Ornament, x 5. USNM 245333.

4. Small ventral valve, a-b, Exterior, interior, x 2. USNM 245334.

5. Ventral valve, a, x 1. b-c, Stereophotographs, exterior, interior, x 2. d-e, Posterior region, x 3. USNM 245335.

6. Ventral valve with coma, a-b, Stereophotographs, exterior, interior, x 2. c, Ornament, x 5. USNM 245336.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L PLATE 6

TETRAPHALERELLA AND FURCITELLA
PLATE 7

FIGURES 1-9. Tetraphalerella cf. T. museulosa (Fenton) <p. L23). USGS loc. 7784-CO.

1. Large dorsal valve, center exfoliated. Note wrinkle in left cardinal extremity, x 1. USNM 245338.

2. Exterior of poorly preserved, large ventral valve, x 1. USNM 245339.

3. Interior, ventral valve, x 1. USNM 245340.

4. Teeth, pseudodeltidium, and muscle scar of large incomplete ventral valve, x 2. USNM 245341.

5. Small ventral valve, x IVa. USNM 245342.

6. Small ventral valve, x IVa. USNM 245343.

7. Interior, incomplete ventral valve, x 1. USNM 245344.

8. Interior, small transverse dorsal valve, a, Interior filled with debris, x 1. 6, Cardinal process lobes, x 2. USNM 245345.

9. Small, complete, poorly preserved specimen with transverse outline, a, x 1.6, Inclined to show pseudodeltidium, x IVa.

USNM 245346.

FIGURES 10-13. Holtedahlina sulcata (de Verneuil) (p. L20). Introduced for comparison to Furcitella cf. F. scofieldi (Winchell and Schuchert) 

(pi. 5, figs. 1-6, and pi. 6, figs. 3-6).

10. Immature dorsal valve. Note cleft medial ridge and sharp posterior-lateral transmuscle ridges, x 2. Whitewater Formation, Morning Sun, Preble County, Ohio. MU-220T.

11. Interior, large dorsal valve, x 2. Whitewater Formation, McDill's Mill, on Four Mile Creek in Preble County, 9 mi. 

north of Oxford, Ohio. MU-221T.

12. Interior of dorsal valve, x 2. Whitewater Formation, Beasley's Creek, north of Camden, Preble County, Ohio. MU-222T.

13. Interior of small ventral valve, x 2. Whitewater Formation, near Oxford, Butler County, Ohio. MU-223T.

FIGURES 14-15. Coolinia subplana (Conrad) (p. L27, L28). Introduced for comparison to Pionomena recens Neuman (figs. 16-31). Note 

medial node.

14. Cardinalia, large specimen, left brachiophore broken, x 2. Waldron Shale, Hartsville, Bartholomew County, Ind. 

MU-224T.

15. Cardinalia, left brachiophore broken, x 2. Waldron Shale, Sandusky, Decatur County, Ind. MU-225T. 

FIGURES 16-31. Pionomena recens Neuman (p. L27). Figs. 16-27, 31, from USGS loc. 5015-CO: figs. 28-30 from USGS loc. 4880-CO.

16. Interior, large dorsal valve, x 2Vz. USNM 245347.

17. Interior, small ventral valve, x 2Va. USNM 245348.

18. Exterior, small ventral valve, x 2V2. USNM 245349.

19. Interior, dorsal valve, x 2V2 . USNM 245350.

20. Interior, ventral valve, a, x 2V2. 6, S.E.M. photograph of right interarea and pseudodeltidium, showing perideltidium, 

x about 12. c, Interarea, teeth, and pseudodeltidium, x 4. USNM 245351.

21. Interior ventral valve, a, x 2x/2. 6, Pseudodeltidium and interarea with perideltidia, x 4. USNM 245352.

22. Interior ventral valve, a, x 2V2. 6, Interarea, pseudodeltidium, and perideltidia, x 4. USNM 245353.

23. Interior dorsal valve, x 2V2 . USNM 245354.

24. Interior dorsal valve, a, x 2Vz. 6, Cardinalia, note medial spine, x 4. USNM 245355.

25. Exterior dorsal valve, x 2V2 . USNM 245356.

26. Exterior dorsal valve, a, x 2V2. 6, Interarea, chilidium, and pseudodeltidium, x 4. USNM 245357.

27. Interior dorsal valve, x 2V2. USNM 245358.

28. Interior dorsal valve, a, x 2V2. 6, Cardinalia and medial node, x 4. USNM 245360.

29. Interior dorsal valve, a, x 2%. 6, Cardinalia and medial node, x 4. USNM 245361.

30. Cardinalia, x 4. USNM 245362.

.31. Cardinalia and medial node, x 4. USNM 245359.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066-L PLATE 7

TETRAPHALERELLA, HOLTEDAHLINA, COOLINIA, AND PIONOMENA
PLATE 8

FIGURES 1-5. Leptaena kentuckiana n. sp. (p. L24). USGS loc. 5136-CO.

1. Paratype, juvenile ventral valve, a, Exterior, x 1. b-c, Stereophotographs, exterior, interior, x 3. d-e, Delthyrial chamber, 

interarea, and teeth, x 4. USNM 245363.

2. Paratype, juvenile ventral valve, a-b, Exterior, interior, x 3. c-d, Pseudodeltidium, delthyrial chamber, and teeth, x 4. 

USNM 245364.

3. Paratype, juvenile dorsal valve, a, x 1. b-c, Stereophotographs, exterior, interior, x 3. d-e, Cardinalia, cardinal process, 

chilidium, sockets, and endospines, x 4. USNM 245365.

4. Holotype, adult ventral valve, a-b, Stereophotographs, exterior, interior, x IVa. c, Enlargement of urnbonal region for 

comparison with figs. 16 and 2a, x 3. d-e, Delthyrial chamber, muscle scars, and teeth, x 2. USNM 245367.

5. Paratype, juvenile dorsal valve, a-b, Exterior, interior, x 3. c, Cardinalia, x 4. USNM 245366.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 1066 -L PLATE

LEPTAENA