THE FOSSIL FRESHWATER EMYDID TURTLES
OF FLORIDA

By

DALE ROBERT JACKSON

A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA
1977

ACKNOWLEDGMENTS

Walter Auffenberg introduced me to fossil turtles and David Webb
increased my interests in paleontology. To both of these men, for their
subsequent time and encouragement, I am deeply indebted. I am very
grateful to the many people who reviewed parts of this paper or who shared
their ideas and knowledge with me: Dennis Bramble, H. Kelly Brooks,
Archie Carr, Stephen Christman, Richard Franz, Carter Gilbert, John
Iverson, Howard Kochman, Carmine Lanciani, Frank Nordlie, Thomas Patton,
Francis Rose, Roger Sanderson, Sylvia Scudder, Graig Shaak, Ernest
Williams, and George Zug.

For their generosity in providing fossils and comparative material
I thank Walter Auffenberg, Walter Dalquest, James Dobie, Harold Dundee,
J. Alan Holman, Farrish Jenkins, Curtis McKinney, Thomas Patton, Robert
Purdy, John Waldrop, David Webb, and Stephen Windham. I am indebted to
Nancy Halliday for instruction and assistance in preparing the illustrations
and to Kay Purinton for the photographs. Lisa Megahee prepared the
figures for Chapter IV and Kenneth Campbell the photographs for Figure
17. Mike Frazier and Greg McDonald were especially conscientious in
collecting and calling pertinent fossils to my attention, and I thank
them for their efforts.

To all others in the Florida State Museum and Department of Zoology
who provided assistance and facilities, I extend my gratitude.

TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ii

TABLE OF CONTENTS iii

ABSTRACT v

INTRODUCTION 1

CHAPTER

I A PLEISTOCENE GMPTEMYS (REPTILIA: TESTUDINES) FROM

THE SANTA FE RIVER OF FLORIDA k

Description of Fossil Sites 4

Description of Fossil Elements 5

Discussion 8

II EVOLUTION AND FOSSIL RECORD OF THE CHICKEN TURTLE

DEIROCHELYS V/ITH A REEVALUATION OF THE GENUS 17

Materials and Methods 18

Fossil Localities 20

Systematic Descriptions 20

Discussion 37

Relationships 39

Distribution and Paleoecology k]

III THE STATUS OF THE PLIOCENE TURTLES CHRYSEMYS CAELATA (HAY)

AND CHRYSEMYS CARET ROSE AND WEAVER 68

Taxonomic Considerations 69

Relationships 72

Discussion 7^

IV A REEXAMINATION OF THE CHRYSEMYS SCRIPTA GROUP BASED

ON FOSSIL EVIDENCE 83

Trachemus in the Pleistocene 85

Tvachemys in the Upper PI iocene 88

Systemat ics 88

Paleoecology 96

Systematic Conclusions 98

Further Problems 101

CHAPTER

V PRE-PLIOCENE RECORDS OF THE GENUS CHEYSEMYS 105

Materials and Methods 1 05

Site Records for Chrysemys IO6

1-75 : : : io6

Seaboard Air Line Railroad Company, Switchyard B . . . 1 06

Thomas Farm 106

Discussion j 09

APPENDIX- FOSSIL LOCALITIES CONTAI N I NG .Z)^//?^^^^!^ 112

LITERATURE CITED 118

BIOGRAPHICAL SKETCH 128

Abstract of Dissertation Presented to the Graduate Council

of the University of Florida in Partial Fulfillment of the Requirements

for the Degree of Doctor of Philosophy

THE FOSSIL FRESHWATER EMYDID TURTLES
OF FLORIDA

By

Dale Robert Jackson
August, 1977

Chairman: Walter Auffenberg
Major Department: Zoology

Limited fossil evidence shows that a turtle of the genus Graptemys
lived in peninsular Florida in the Santa Fe River during the Pleistocene.
The small sample of available material, including elements of both
Ranchol abrean and Blancan periods, indicates that this turtle occupied the
river throughout most of the Pleistocene before becoming extinct in that
drainage. The apparent affinities of this turtle with Recent G.
barbouri of the Apalachicola River system bring up several geologic and
zoogeograph ic considerations.

Prior evidence of the fossil history of the monotypic genus
Deirochelys is limited to a single Upper Pleistocene fragment and a number
of Subrecent elements from Florida. On the basis of several morphological
adaptations unusual among emydine turtles (e.g., neural bone width and rib
structure), fossils from twenty Florida sites, ranging from Miocene to
Subrecent in age, are referred to the genus Deirochelys . Evidence of the
gradual evolution of a suite of characters associated with a gape-and-suck
method of feeding is presented. The Middle Pliocene representative of the

genus is recognized as a distinct species which, like the Miocene fossils,
is intermediate between modern D. retioularia and less specialized
emydines such as Chrysemys.

Reexamination of type and referred materials indicates that C.
carri Rose and Weaver is indistinguishable from Chrysemys oaelata (Hay).
Chrysemys oaelata is a characteristic member of Hemphillian faunas of
Florida and appears to be immediately ancestral to C. nelson-i.

Fossil members of the Chrysemys soripta group (subgenus Trachemys)
in Florida are reexamined and compared to fossil Chrysemys from other
parts of North America. Designation of the Rancholabrean subspecies
C. s. petrolei is confusing and biologically unrealistic. Cranial material
of C. platymarginata affirms the Trachemys affinities of this Blancan
turtle described from Florida. However, a morphological comparison of
C. platymarginata with C. idahoensis , described from the Upper Pliocene
of Idaho, reveals that the two may be conspecific. Additional material
from the Great Plains supports this hypothesis. The phylogeny proposed
in 1967 by Weaver and Rose, in which the C. soripta group is believed
to be more closely related to the C. rvbriventris series than either is
to the C. floridana series, is rejected in favor of that proposed by
McDowell in 196^4, in which the last two series are more closely related
to each other than either is to the C. soripta group.

All pre-Pl iocene records of the genus Chrysemys are reexamined.
Patton's 1969 report of Chrysemys from a nonmarine Oligocene deposit in
Florida cannot be confirmed. Fragments assigned to the genus by Olsen
from a Miocene deposit in the Florida panhandle actually represent a
sea turtle and land tortoise. Chrysemys is present in the Thomas Farm

Miocene fauna, although some material previously assigned to the genus
may represent Deiroohelys.

INTRODUCTION

The family Emydidae, including nearly 30 living genera and 80
species, is the largest of all turtle families. Its essent ial 1 y circum-
global distribution (excluding Australia and subsaharan Africa) makes
it the most widely distributed of all nonmarine turtle families.
Emydids are especially well-represented in southeastern Asia and the
southeastern United States and are the dominant family of turtles in
North America (Auffenberg, 197^; Mount, 1975).

A major step in understanding evolution of the modern chelonian
fauna lies with clarification of the relationships and evolutionary
processes that have occurred within the Emydidae. Although in the last
two decades considerable significant comparative work in this field has
been accomplished through the techniques of serology {e.g., McKown,
1972; Merkle, 1975), cytogenetics {e.g., McKown, 1972; Bickham, 1975;
Bickham and Baker, 1976), and comparative morphology {e.g., McDowell,
196A; Waagen, 1972; Bramble, 197^*), inadequate attention has been paid
to the direct evidence provided by the fossil record.

Freshwater emydid turtles in the southeastern United States, and
especially those in Florida, are wel 1 -represented in vertebrate fossil
deposits. This paper attempts to reevaluate, expand, and coordinate
our knowledge of these turtles as reflected by their fossil record.
In addition to systematic and evolutionary cons iderat ions, ecolog ic
and biogeographic implications are discussed. The geographic domain
of this paper is Florida, although the relationships of turtles from

this area cannot be meaningfully discussed without comparisons to
turtles from other regions of North and Central America.

Although probably originating in the Late Mesozoic, the Emydidae
are unknown as fossils before the Tertiary. The family Is well-repre-
sented in several Eocene formations in Western North America, primarily
by the presumably extinct genus Eohmatemys. Most modern genera remain
unknown as fossils until the Miocene or later. The geologic youth of
Florida restricts the present work to Oligocene and younger strata;
hence, early evolutionary paths within the family will not be found
here.

By far the most important early thrust in chelonian paleontology
was Oliver Perry Hay's (1908) "Fossil turtles of North America," in
which he discussed extensive Pleistocene and older material from
Florida. Since then, little work was done in Florida until the late
1950*5 and 1960's, when there occurred a resurgence of interest in
fossil emydids. Most significant are the works of Weaver and Rose
(1967) and Weaver and Robertson (1967), which deal with the genus
Chrysemys, and a series of papers by Mil stead and Auffenberg (Milstead,
1956, 1967, 1969; Auffenberg, 1958; Milstead and Tinkle, I967) on box
turtles (Terrapene) . As the latter have been thoroughly studied, I
shall not deal further with Terrapene.

The following work consists of five sections each dealing with
a distinct taxonomic unit. The first section, details the first known
occurrence of Gvaptemys harbouri in the fossil record and the first
fossil record of the genus in Florida. The second section describes
a remarkable collection of fossils that clearly outline the direction
of evolution in the previously poorly known genus, Deirochelys. The

third revises the relationships of two Middle Pliocene turtles of the
genus Chnjsemys. The fourth presents a new interpretation of the
Chryserrys scripta complex based on a comparison of fossils from Florida
with those from the midcont inent , and the fifth reexamines the Miocene
and Oligocene fossils previously assigned to the genus Chryserrys.

As elements of the shell are by far the most frequently found and
readily recognizable turtle fossils, it is primarily with these that I
have worked. Many adaptive characters are reflected by shell morphology.
Cranial material is used when available, although it is unfortunately
scarce in most fossil deposits. Chelonian limb elements are generally
of little systematic value at the specific level and are very rarely
found in association with shells in Florida deposits.

CHAPTER I
A PLEISTOCENE GRAPTEMYS (REPTILIA: TESTUDINES)
FROM THE SANTA FE RIVER OF FLORIDA

Prior to this study the genus Graptemys has not been reported in
the southeastern United States east of the Apalachicola River system
in western Georgia and the Florida panhandle. All valid records indi-
cate that the eastern-most species, G. barbouri , is presently endemic
to the Apalachicola drainage (Cagle, 1952; Carr, 1952; Dobie, 1972;
Wharton et al . , 1973). Fossil elements from the Santa Fe River in
northern peninsular Florida now prove that a turtle of this genus did
occur there during the PI io-Pl ei stocene. The close alliance of this
turtle with modern G. barbouri suggests the importance of Pleistocene
physiographic changes to the distribution of these animals. The
discovery of this fossil form adds to our limited knowledge of the
fossil history of the genus, previously summarized by McKown (1972).

Description of Fossil Sites

The Santa Fe River in northern peninsular Florida has previously
been described by Hellier (1967); it is presently one of the major
tributaries of the Suwannee River. All fossils were obtained from two
adjacent sites in the Santa Fe at the Columbia/Gilchrist county line
(29°50'N, 82°42'W), well downstream from the subterranean portion of
the stream's course. Both sites are bottom deposits with reworked
bone. Santa Fe I is a heterochron i c deposit containing material from
both the Rancholabrean (late Pleistocene) and Blancan (Upper Pliocene)

periods; it normally lies under 6 to 8 m of water. Fossils representing
the two ages from this site may generally be distinguished by their
state of preservation; Blancan elements are often a glossy black in
contrast to the coarse brown Rancholabrean material. Santa Fe II , which
lies in 2.5 to 3 m of water approximately 100 m downstream from Santa
Fe I, contains only Rancholabrean material. Site ages have been well-
established on the basis of their mammalian faunas (Hibbard ,et .a!.,
1965; Webb, 197^).

Description of Fossil Elements

Three elements positively representing the genus Graptemys are
available: a third neural, a nearly-complete nuchal bone, and the major
portion of a mandible (Fig. 1). A right hyoplastron representing either
a Graptemys or a small Chrysemys concinna is also described. All
specimens are in the Florida State Museum (UF) and the Timberlane
Research Organization (TRO).

Nuchal bone. A nearly-complete nuchal bone (UF 10572) from Santa
Fe I was collected by B. Waller and R. Allen in 1963. The very broad,
short nuchal scute is characteristic of Graptemys. Although the dorsal
midline of the bone is conspicuously elevated, the distinct keel usually
present in G. barbouri is lacking. However, Roger Sanderson (pers.
comm. ) , after examining several hundred G. barbouri , believes this
character to be of little taxonomic significance. Dimensions of the
fossil are width of anterior border--approx. 35-6 mm; max width--
approx. 69.8 mm; length of anterolateral border--8.1 mm; max length--
47.8 mm; length of nuchal scute — 3.6 mm. Estimates based on these
measurements place the fossil turtle between 210 mm and 230 mm cara-

pace length (CL), corresponding to a plastron length (PL) of 180 mm

to 197 mm; carapace width (CW) is estimated at roughly 190 mm to 200

mm. These dimensions correspond to those of Recent adult female

G. barbouri although the carapacial width is relatively greater.

State of preservation indicates that this turtle is probably Blancan in

age.

Neural bone. A large Graptemys neural bone (TRO 100) was found
in 1961 at Santa Fe 11 by J. Waldrop and D. Bell. The distinct keel
ending abruptly in a blunt knob midway back along the midline of the
neural indicates that this is the third neural of a G. barbouri-] \ke
turtle. Dimensions of the bone are max length--30.6 mm, max width
(anterior margin, lateral border) --30. 5 mm; min width (posterior margin,
lateral border)-- 18. 0 mm; max thickness, lateral border--10.0 mm.
Except for the more rapid tapering from anterior to posterior borders,
the neural appears to be that of a very large G. barbouri (estimated
CL = 270 mm to 280 mm; PL = 230 mm to 240 mm).

Mandible. The only available data for the partial lower jaw
(US 19161) is the collection site, Santa Fe II. The broad alveolar
surfaces as well as the size of the jaw indicate that this turtle had
an extremely large head modified for crushing hard food such as mollusks.
This structure and habit is characteristic of females of the sexually-
dimorphic extant forms, G. barbouri and G. pulohra. The fossil mandible
appears almost identical to that of a Recent adult female G. barbouri,
except that the alveolar surfaces of the fossil are less expanded
posteriorly (possibly a function of ontogenetic change), and the two
halves of the jaw meet at a slightly wider angle than in the Recent

form. Dimensions of the fossil elements are approx. max width
(excluding articulating surface) --5'^ mm; max width of alveolar surface--
18.6 mm. Comparison with Recent G. hai'bour'-i yields an estimated
carapace length for this individual of 230 mm to 290 mm (assuming
skull rshell ratios to be approximately the same in Pleistocene and
Recent forms) .

Hypopl astron . The only data for the right hypoplastron (UF 192^46)
is Santa Fe 1. The thin, flat nature of the piece, the very narrow zone
of scute overlap on the dorsal surface, and the straight anterior
border {i.e., the absence of an obvious concavity into which the ento-
plastron fits, as in most Chrysemys) Indicate that this element may be
from Grapteniys . However, l:ypoplastra of some individuals of Chrysemys
eoYicinria, a common turtle of both the Pleistocene and present in the
Santa Fe River, also fit this description, and the element may belong
to a small Individual of that species. The dimensions of the bone are:
max length--62.7 mm; width from midline to anterior, ventral edge of
axillary notch--A8.5 mm; max thick^-iess along hyo-hypopl astral suture--
k.k mm. State of preservation Indicates a probable Blancan age.

Based on available material it is concluded that the Santa Fe
Grcwtemys vjas a sexually-dimorphic form (or forms) very similar to G.
harhouvi in both structure and habits. Maximum adult body size was
probably slightly greater than that attained by modern G. barbouri.
The shell may have been somewhat broader and the keel less pronounced
than in extant G. barbouri . Pending acquisition of further material
which inay show the Blancan, Ranchol abrean , and Recent forms to represent
two or even three distinct forms, all the Santa Fe Graptetnys are

tentatively referred to Graptemys cf. G. harbouri Carr and Marchand.
Erecting further names for these allochronic forms is presently un-
warranted.

Di scussion

Accounting for the presence of G. harbouri in the Suwanee drainage
during the Pleistocene requires consideration of several geologic and
zoogeographic phenomena. Mainly because Graptemys rarely if ever travels
on land (McKown, 1972), endemism to a single river system is character-
istic of several species of the genus--G. versa, G. ooulifera, G.
flavimaculata, and for all intents and purposes, G. nigrinoda (Cagle,
195/4; Folkerts and Mount, 1969; Conant, 1975). Since Dobie (1972)
eliminated Cagle's (1952) apparently-erroneous record for the Escambia
River in western Florida, all remaining records indicate that G.
barbouri likewise developed as an endemic species in the Apalachicola
River system. The presence of a Pleistocene turtle, here believed to
be conspecific with Recent G. barhouri (although the problem remains
essentially the same even if it were later shown to be a distinct
species of common ancestry), in a drainage system which empties into the
Gulf of Mexico approximately I85 km from the mouth of the Apalachicola
requires comment. Several explanations are suggested.

The eustatic changes in Pi io-Pl ei stocene sea levels, corresponding
to the formation and melting of the Ice Age glaciers, are well-known
phenomena. During glacial periods the retreating sea exposed a much
larger expanse of the Floridian Plateau (that portion of the continental
shelf surrounding Florida and extending far out into the Gulf-Cooke,
191,5) than is now above sea level. Frey (1965) has stated that this

eustatic lowering of the sea level reached a maximum of 120 m below
present sea level, and during the Wisconsinan glacial episode some
20,000-18,000 years ago exposed up to a 210 km wide stretch of con-
tinental shelf (Fig. 2). Donn et al. (1962) have calculated that
minimum sea level came even earlier, in the lllinoian glacial period,
when the sea dropped to between ]hO m and 1 60 m below its present
level. Conceivably such a drop in sea level could bring about the
confluence of many rivers which now empty directly into the Gulf. Con-
tinuation of the Apalachicola and Suwannee Rivers beyond their present
mouths would create a hypothetical junction between them (Swift, 1970)
near the expected western-most coastline of Pleistocene central
peninsular Florida. However, the absence of large numbers of fish
species common to both rivers as well as intervening drainages discredits
this idea. Nevertheless, even if convergence of the two rivers did not
occur, a lowland marsh between the two could have allowed turtles to
migrate from one stream to the other. If this were the case the
occurrence of a G. barbouvi- \\ ke. turtle in two presently widely sep-
arated rivers could thus be explained. Furthermore, if the present
absence of Graptemys fossils from the Suwannee north of its junction
with the Santa Fe reflects a real situation, then it may be that the
ancestral (upper) Suwannee was captured by a stream (the present lower
Suwannee, including the Santa Fe) eroding eastward from the Gulf of
Mexico during the PI io-Pl ei stocene (Vernon, 1951; Brooks, 1966).
Whether this stream was confluent at one time with the Apalachicola is
not presently known. Evidence shows that prior to this time the
ancestral Suwannee likely emptied into the Gulf south of its present

10

mouth via connection with the present-day Waccasassa River (Vernon,
1951 ; White, 1970).

A second possible migratory route which may have been followed by
the ancestral G. barbouri involves the upper reaches of these rivers.
Although Graptemys rarely wanders overland it is conceivable that under
some conditions (e.g., flooding) a few individuals may move to an
adjacent stream. Figure 2 reveals the proximity of the Flint River, a
major tributary of the Apalachicola in which G. barbouri is known to
occur (Cagle, 1952; Wharton et al., 1973; R. Franz, pers. comm.), to the
upper reaches of the Wi thl acoochee and Alapaha Rivers, both of which
empty into the Suwannee. The distances may have been even less during
the Pleistocene had the waters been significantly higher or the courses
of the rivers different than they are now; the latter possibility is
especially likely in this area of sand- 1 imestone substrate. Further-
more, certain fishes common to the two drainages suggest direct
communication at some time in the past between the upper reaches of
these two rivers (C. Gilbert, pers. comm.). Yerger and Relyea (I968)
explain the distribution of laixzlurus serracanthus --knovjn only from
the Apalachicola, Ochlockonee, and Suwannee drainages — by stream piracy
following closure of the Suwannee Straits (Pl io-Plei stocene) . They
suggest that stream capture between tributaries of the Ochlockonee
(until relatively recently a part of the Apalachicola drainage) and
the upper Suwannee may have accounted for a westward migration of this
fish from the Suwannee into the Apalachicola. It is likely that stream
capture between tributaries of these same rivers or between the Flint
and upper Suwannee may account for the occurrence of G. barbouri in
these two drainages. Its apparent absence (both Pleistocene and Recent)

11

from the upper Suwannee and Ochlockonee may reflect inadequate collect-
ing or unsuitable habitat.

A third possibility, not necessarily exclusive of either of the
preceding two, is that G. harbouri has not always been restricted to
one or two widely separated rivers but was more widespread than pre-
viously thought. The long period of relatively stable environmental
conditions during the Blancan may have been conducive to the expansion
of G. barbouri' s range throughout much of the seemingly favorable
limestone-underlain habitat between the two rivers. Thus it is postu-
lated that at various times G. barbouri occurred (though perhaps in
relatively low densities) in most or all rivers between the Apalachicola
and Suwannee. In addition to explaining the presence of this turtle in
two widely separated rivers as simply its occurrence at the ends of a
nearly-continuous range, the idea also seems compatible with the dis-
tribution of the remaining southeastern members of the genus. The
occurrence of G. kohni in the rivers of eastern Texas and Louisiana
(Conant, 1975), G. pulchra from the Pearl River to the Escambia and
Yellow Rivers in western Florida (Dobie, 1972), and G. barbouri from
the Apalachicola to the Suwannee River, would provide a nearly-
continuous range of large, ; --ixual ly-d imorphic Graptemys of the wide-
headed female line (Cagle, 1953; McKown, 1972) in the river systems
draining the entire northern shore of the Gulf of Mexico. The only
apparent gap is the Choctawhatchee River System between the ranges of
G. pulchra and G. barbouri (Dobie, 1972) (Fig. 2).

Ultimately the solution to this question may lie with the collec-
tion of further fossil evidence and with detailed studies of the dis-

12

tributions of other lotic organisms. Current investigations on fish
and snail faunas of these and other river systems in the southeastern
United States may help provide an answer.

The reasons for extinction of the Santa Fe Graptemys remain
speculative. At present the river seems sufficiently similar to Carr
and Marchand's (19^2) description of ideal G. barbouri habitat to support
a population of these turtles; this seems to be further indicated by
the fact that lotalurus serraaanthus , which also seems to prefer rocky,
clear streams with moderate flow, still inhabits the Santa Fe today
(Yerger and Relyea, I968). From the paucity of fossil material Graptemys
was apparently never common in the Santa Fe. In comparison to the few
Graptemys fossils over 500 elements of Chrysemys aonainna, C. nelsoni,
and C. scripta have been collected from the same sites. Even though
C. oonoinna is abundant in the Santa Fe today its habits are sufficiently
distinct (and presumably were in the Pleistocene) from those of G.
barbouri that significant competition between the two turtles would
have been unlikely. More probably, climatic changes or physical changes
in the topography of the land or in the river itself made the habitat
unsuitable at some time in the past for the small population of Graptemys,
or possibly for the mollusks upon which the females presumably fed.

Figure 1. Fossil Graptemys elements from the Santa Fe River,

Florida. (A) nuchal; (B) mandible; (C) , (D) third neural
dorsal and lateral aspects.

14

Figure 2. Southeastern United States and Gulf of Mexico, showing
range of Graptemys pulahra and G. barbouri . Diagonal
hatching, approximate range of G. pulahra (northern
boundary indefinite); horizontal hatching, reported range
of G. bavbouvi; triangle, Santa Fe River sites I and II;
dotted line, 120 - meter contour showing approximate
coastline during maximum eustatic lowering of sea level
in the Quaternary (after Frey, I965); rivers mentioned
in text:

1- Pearl 6. Apalachicola 10. Alapaha

2. Escambia 7. Ochlockonee 11. Suwannee

3- Yellow 8. Fl int 12. Santa Fe

h. Choctawhatchee 9. Wi thlacoochee I3. Waccasassa

5. Chipola

]6

n

CHAPTER I I
EVOLUTION AND FOSSIL RECORD OF THE CHICKEN TURTLE
DEIEOCHELYS WITH A REEVALUATION OF THE GENUS

The evolutionary history of the monotypic genus Deiroahelys is
one of the more enigmatic chapters in our knowledge of North American
emydine turtles. Previous workers (Carr, 1952; Loveridge and Williams,
1957; McDowell, 196^) have generally agreed that Deiroahelys is a highly
specialized derivative of the genus Chrysemys (sensu McDowell, 196^*).
Furthermore, Baur's (I889) suggestion of a close phylogenetic relation-
ship between Deiroahelys and another North American monotypic emydine
genus, Emydoidea, has been supported by most subsequent workers
(Loveridge and Williams, 1957; Jackson, 1959; McDowell, 1964; Zug and
Schwartz, 1971). Recently Waagen (1972) and Bramble (1974) have cast
doubt on this idea based on their respective studies of musk glands and
shel 1 mechan ics .

The fossil record has been of no help in these matters to date.
Prior knowledge of the fossil history of the genus Deiroahelys is
limited to description of one partial nuchal bone from the Upper
Pleistocene of Florida (Jackson, 1964, 1974a) and to mention of the
presence of D. reticularia in a Subrecent Florida site (Hirschfeld,
1968). Jackson (1974a) suggested that the Pleistocene element
representsa turtle which is conspecific with modern D. reticularia.
All other fossils assigned to the genus, i.e. Deiroahelys floridana
Hay and Trachemys jarmani Hay (Hay, I908; Weaver and Robertson, I967),
actually represent the genus Chrysemys (Jackson, 1964, 1974a).

17

This paper examines material referable to the genus Deirochelys
from one Miocene, five Pliocene, twelve PI ei stocene, and two Sub recent sites,
all in Florida. The Miocene fossils are the oldest known representatives
of the genus. Two species of Deirochelys, one new, are recognized as
fossils. As will be shown the major course of evolution within Deiro-
chelys has been the extreme elongation of the head and neck, a condition
achieved by only one other emydine genus [Emydoidea) and presumably
developed as a trophic specialization. The accompanying cervical
musculature hypertrophy has necessitated further structural modifications
of the shell and vertebral column. It is for this reason that in trac-
ing the evolution of the genus I dwell primarily upon this cervico-
cranial elongation and associated morphological modifications (e.g.,
changes in neural bone width and rib and vertebral structures), to
which I collectively refer hereafter as a single "character suite."

Materials and Methods

All fossil specimens except those from Waccasassa River and a few
from Thomas Farm are part of the vertebrate paleontology collection of
the Florida State Museum (UF) ; the Waccasassa River I specimens are
from the Timberlane Research Organization (TRO) , Lake Wales, Florida,
while some of the Thomas Farm fossils are from the collections of the
Museum of Comparative Zoology, Harvard University (MCZ) . Comparative
skeletal material was examined from the herpetology collection of the
Florida State Museum (UF), the National Museum of Natural History
(USNM), and my personal collection (DRJ). Extant specimens examined
were Deirochelys reticularia : DRJ 264, 266, 270, 27^4, 278-280, UF

19

li»20, llkk, \hlkk, USNM 11610, 11615, 29^77, 29584, 62219, 80965,
95789; Emydoidea hlandingii: UF 1^42^*9, 18931; Chelydra serpentina:
DRJ 253; Chelys fimbriata: UF 21977-

A shell thickness index (STI) was determined for most fossils.
Thicknesses of fossil shell elements were measured and divided by
corresponding measurements of a series (N = 10) of Recent adult D.
retioularia of corresponding size, or by linear extrapolations to pro-
duce such if no modern turtle of sufficient size could be found. As
the relationship between shell thickness and body length may be
asymptotic rather than strictly linear, the STI values given for the
largest fossils may actually be underestimates. There was little
individual STI variation among the Recent turtles when corrected for
differences in body length. More medial elements (neural bones and
proximal ends of pleural bones) generally yielded slightly higher STI
values than peripheral elements (peripheral, pygal , and nuchal bones),
indicating that increase in shell thickness is not necessarily pro-
portional for all parts of the same shell. Medial edges of peripheral
elements were measured to reduce this discrepancy.

An index of free rib length (width of rib canal) was determined
by dividing the stra ight- 1 ine distance from the proximal tip of the
pleural bone to its union with the rib by the width of the pleural bone
at the level of the union. The fragmented condition of most of the
fossils necessitated the use of pleural bone width rather than length.
In comparing neural and pleural bones of fossil Deiroohelys with
those of Recent turtles, it is necessary to determine which of the
eight neural or pleural bones the fossils represent. The presence

20

and position of scute sulci as well as the relative proportions of the
anterolateral and posterolateral borders of the bones usually make this
possible. Because of the relatively great width and frequent anomalies
of the posterior neural bones of most emydine turtles, these bones are
of little taxonomic value.

All measurements are maximum and given in mm.

Fossi 1 Loca 1 i t ies

The appendix provides an annotated list of Florida localities that
have yielded fossil Deivochelys mentioned in this paper. Reference is
made to other publications in which stratigraphy, pa 1 eoecology , and
correlative age of each of these deposits is described in detail.
Figure 3 shows the geographic distribution of these sites.

Systematic Descriptions

All past descriptions of the genus Beivochelys (Agassiz, 1857;
Baur, 1889; White, 1929; Schwartz, I956; Jackson, 1959; McDowell, 196^1;
Zug and Schwartz, 1971) have necessarily been drawn solely from the
single extant species, D. reticularia. Hence, many characters which '
would have been more appropriately designated as specific characters,
particularly those involving color pattern, have been incorporated
into the definition of the genus. Therefore, in order to accommodate
the fossil members of the genus it is necessary to relegate many of
the generic characters, including all references to color pattern, to
specific level. Additionally, an examination of osteological char-
acters through time reveals phylogenetic changes within the genus that

21

may be used to distinguish certain allochronic forms. For these reasons
I find it necessary to give a brief systematic reevaluation of the genus
as a prelude to a formal description of the fossil forms. The present
chronologically-expanded definition of the genus, like those of Baur
(1889), White (1929), Jackson (1959) and McDowell (1964), is based
solely on osteological characters. As fossil skull material is unknown,
all skull characters are drawn from modern Z). retioularia. Schwartz
(1957) gives a brief but adequate account of the taxonomic history of
the genus.

Fami 1y Emyd idae

Subfamily Emydinae

Genus Deiroahetys Agassfz

To the generic synonymy given by Zug and Schwartz (1971) should
be added the following entry:

Hiroohelys Beyer, 1900: k5-

Type. Testudo reticularia Latreille.

Referred species. Beivochely s ret-iculax'ia , the only extant
species, presently distributed throughout the southeastern United
States and known from the Pleistocene of Florida; Deiroohelys carvi ,
n. sp.. Pliocene Alachua clays of Florida, Hemphill ian age.

Def ini t ion. Shell elongate to subovate in adults; carapace
elliptical or cuneiform in outline and usually sculptured with fine
parallel ridges or scales (Fig. k) ; anterior edge of nuchal bone
generally truncate and acuminate; lateral sulci of nuchal scute
usually parallel above and below; nuchal scute usually two to three

22

times longer than wide above, approximately as wide as long below;
nuchal bone overlapped only by small corner of first costal scute or
not at all; vertebral scutes as wide as long; neural bones hexagonal,
short-sided in front; first neural bone circular to subovate in out-
line; other neural bones generally as wide or wider than long (Fig. k) ;
peripheral bones unnotched; pygal bone approximately paral 1 el -s ided
with a shallow mesial notch; ribs dorsally free from pleural bones
well below proximal ends of pleurals, their free portions slender and
bowed ventral ly (Fig. 5) accommodating the enlarged trunk vertebral
muscle complex (Shah, 1963).

Plastron usually considerably narrower than carapace, akinetic,
and firmly united to carapace by a high bony bridge and plastral
buttresses; inguinal scutes large [contrary to Holman's (1967) state-
ment that they are absent]; plastron smooth ventral ly or with traces
of sculpturing similar to but less pronounced than that of carapace;
entoplastron usually anterior to humeropectoral sulcus and overlapped
by gular scutes for approximately one third of length.

Skull and second through seventh cervical vertebrae elongate;
neural spines of anterior thoracic vertebrae laterally compressed as
vertical sheets (Fig. 6); triturating surfaces of maxilla and mandible
narrow, without ridges; beak never hooked; interorbital width very
narrow, less than one-half diameter of orbit; palate decidedly flat;
posterior palatine foramina much larger than foramina orbi to-nasal e
(Gaffney, 1972) (= anterior palatine foramina of Hoffman, I89O);
temporal arcade complete; quadrate nearly enclosing stapes; hyoid
apparatus strongly developed, lateral horn length at least as great as
skull width; cervical musculature as described by Shah (1963).

23

A specialization of the genus almost certainly related to the
elongate neck and hypertrophied vertebral musculature is the modification
of the spinal column. The differences between DeivochBlys and more
primitive emydines {Chrysemys, Echmatemys) , summarized in Table 1 and
Figure 6, are most conspicuous in the first four thoracic vertebrae.
In both forms ribs attach intercentral 1 y and the thoracic vertebrae
are united by their neural spines to the overlying neural bones. The
net effect of these modifications in Deiroahelys has been to move the
rib attachment ventral ly (away from the carapace), allowing for the
hypertrophied trunk vertebral musculature without changing the distance
of the spinal cord from the ventral surface of the carapace.

Deiroehelys reticularia (Latreille)
Chicken Turtle

The only addition to the species synonymy listed by Zug and
Schwartz (1971) is:

Hirochelys reticulata Beyer, 1900:^45.

Type: The type was formerly in the collection of the French
Museum National d'Histoire Naturelle but is now considered lost
(Schwartz, 1956). Schwartz (1956) described a neotype^ and neoallo-
type from the vicinity of the original type locality.

Type local i ty. Restricted by Harper (19^0) to the vicinity of
Charleston, South Carolina.

Diagnos i s : A Dei-vochelys characterized by relatively low length:
width ratios for third through fifth neural bones (means, 0.6 to 0.7;

2k

Table 1. Comparison of the thoracic vertebrae of

Deiroahelys and Chrysemys .

Character

Chrysemys

Neural spines low and robust

Deirochetys

laterally compressed as
vertical sheets

Centra

narrowest ventral ly;
not compressed

narrowest dorsal ly;
dorsoventral ly compressed
ventral surfaceswide and
f 1 attened

S i te of rib
attachment
to vertebra

expanded dorsal
region of
centra

expanded ventral region
of centra

25

Fig. 7) and relatively great length of free portions of dorsal ribs
(Fig. 8); coloration as described by Schwartz (1956) with notation
that the yellow forelimb band is usually but not always wide; neck
nearly as long as plastron; usual pattern of cervical central
articulation (perhaps a generic character): (2( (3( (4) )5) )6) )7(
(8) (Williams, 1950; Jackson, I97^b).

Description of fossil material. The following fossils, listed in
reversed chronologic order by site, are here assigned to D. ret-Loularia,

Nichoi's Hammock: contains more D. ret-icularia than any other post-
Pliocene site; 75 carapacial elements (UF 20892), a cervical vertebra
(UF 209OA), and a supraocci p i tal crest (UF 20905) represent 12 to 20
individuals ranging from 65 mm to 195 mm carapace length (CL) ; many
additional elements from this deposit, particularly plastral and
peripheral bones which lack diagnostic features, probably represent
D. reticutaria as well; fossils from the site are indistinguishable
from modern D. retioularia, their shallow rugosity probably reflect-
ing their relatively small size; STI 0.95 to I.05.

Warm Mineral Springs: To date, 35 elements - one nuchal, seven neural,
one suprapygal, six pleural, 13 peripheral, and five plastral bones,
plus a scapula and broken femur - all assigned field number WMS 19352
and representing five to ten individuals of CL 1 38 to 18^4, have been
removed from this site. The bones are similar to those from Nichoi's
Hammock and have an average ST! of 1.15-

Vero: A large number of plastral and carapacial elements, including
at least two nuchal, two neural and two pleural bones (all recently

26

acquired by the Florida State Museum as part of the former Florida
Geological Survey collection and as yet uncatalogued) are virtually
indistinguishable from modern D. reticularia; ST! O.85-O.95.

Waccasassa River I: Two second neural bones (TRO 101, 102) and a third
neural bone (TRO 103), representing three individuals of I30 to 210 CL
(Fig. 9); STI 1.1 to 1.3-

Waccasassa River V: A lightly-sculptured nuchal bone, UF I627I (Fig.
9): greatest length 30.5, greatest width 35-5, estimated CL 135;
proximal end of a pleural bone, UF 16275; STI 1.1.

Waccasassa River VI: A distinctly grooved nuchal bone, UF 2I906:
greatest length 39-8, greatest width 42.3, estimated CL 170; STI 1.1.

Reddick IIC: A first neural bone (UF 21955) from an adult turtle
(estimated CL I80) and the proximal end of a fourth pleural bone from
a juveni le; STI 1.1.

Coleman IMC: Four elements (UF I5I86E) representing at least three
individuals: a longitudinally rugose, relatively deeply notched pygal
bone (length 21.5); a left epiplastron ( interep i plast ral suture length
13.6); a characteristically rugose left xi ph i pi ast ron missing its distal
portion (hypo-xiphiplastral suture length ^40. 7); and a distinctly
sculptured right hypoplastron ( interhypoplast ral suture length 58.4);
STI 1.3.

St. Petersburg, Catalina Gardens: Lower two thirds of a right fifth
pleural bone (UF 19248): greatest width 30.0, estimated length 60,
estimated CL 220; STI 1 .3.

27

Seminole Field: A deeply sculptured fragment of a right second pleural
bone (UF 9927) with rib attachment - width at rib level 28.0, thickness
at rib level 5-9, estimated CL 210; fragment of a left hypoplastron
(UF 9927) with deep longitudinal grooves on ventral surface, estimated
CL 210; STl 1 A.

Bradenton 5!st Street: A characteristically sculptured fragment of a
nuchal bone (UF 2482): estimated CL 210, STl 1.25.

Kendrick lA: A sixth neural bone (UF 19250) with a pronounced, scale-
like sculpturing and a low, rounded keel - greatest length 19.3, greatest
width 33.2, greatest thickness 6.0, estimated CL 250, ST! 1.3; a deeply
grooved partial nuchal bone (UF 9292) possibly from the same individual
and described previously by Jackson (1964): estimated CL 250, STl l.I
to 1.6; (Fig. 10).

Wall Company Pit: Proximal halves of two broken pleural bones (UF 5026):
a second left (estimated CL 175, STl 1.6) and a deeply rugose fourth
right (estimated CL 220, STl I.5) with rib distance: pleural width
ratios of 0.84 and O.8O, respectively.

Haiie XVI: 38 elements representing at least 15 individuals of CL 116
to 240: a nuchal bone (UF 20896) , length 40.0, estimated CL 182; a
second neural bone contiguous with the second and third right pleural
bones (UF 20888; Fig. 11), and the first left and second right periph-
eral bones (UF 20889) almost certainly from the same individual,
estimated CL 230; fifteen fragmentary pleural bones (UF 20895; UF 20898)
and seven peripheral bones (UF 21970); a hypoplastron (UF 2I969) and

28

partial hypoplastron (UF 21968); contiguous second, third and fourth
neural bones (UF 20893) from a turtle of 227 CL; and the third
(UF 20897), fourth (UF 21971), two fifth (UF 20894 and UF 20898) , and
sixth (UF 20898) neural bones from five turtles with CL of 240, ]kO,
225, 160 and 220, respectively. Neural length: width and rib distance:
pleural width ratios are included in Figs. 7 and 8; STI of neural
bones 2.0 to 2.2.

Haile XV: A fifth neural bone (UF 192^9), the dorsal surface of which
is extremely flat but moderately sculptured: greatest length 20.2,
greatest width 32.0, estimated CL 210; an anterior fragment of a nuchal
bone (UF 19168), estimated CL 230; STI 1.5; (Fig. 12).

Discussion of fossil material. All of the Ranchol abrean and
Subrecent material is clearly referable to D. retiaularia. With the
exception of shell thickness, relative dimensions of individual fossils
show no significant differences from corresponding measurements of extant
turtles. The Blancan and Irvingtonian material, as well as the Kendrick
nuchal, indicate that this species reached a slightly larger maximum
size during the Late Pliocene and Pleistocene than at present. The
blunt median keel on the Kendrick neural, although not typical of most
extant D. reticulavia, occurs posteriorly in a few individuals. Though
tending to be more pronounced in the Pleistocene, shell rugosity
patterns are within the range of variation of modern B. veticularia.

The single consistent difference between Pleistocene and Recent
D. veticularia is that of shell thickness. The STI of Pleistocene D.
veticularia is I.l to 2.2 times that of Recent turtles. The trend

29

towards shell thickness reduction appears roughly chronoclinal since
at least the Irvingtonian (Table 2), though the absence of material
from some glacial and interglacial periods may conceal unseen fluctua-
tions. Similar trends in post-Pliocene shell thickness reduction have
been suggested, though less well supported by a t ime-t ransgress i ve
series of fossils, for Chvysemys (Preston, I966, 1971), Emydoidea
(Taylor, 19^3), Graptemys (Chapter l)^ Kinosteimon (Fichter, 1 969),
Trionyx (Wood and Patterson, 1973) and Geochelone (Auffenberg, 1963b).
Although shell thickness alone is inadequate as a basis for taxonomic
separation, it is not a simple function of turtle size as Auffenberg
(1958) states for Terrapene. From Middle Pleistocene to the present,
the shell of D. reticularia has become progressively thinner. Gaps
in the STI-time curve may reflect our incomplete sampling of the
fossil record. Nevertheless, the possibility of sexual and ontogenetic
polymorphism in this character, as well as hidden fluctuations in the
curve, could complicate the matter. Unfortunately, sample sizes from
most fossil sites are inadequate for a thorough treatment of the data.

The Irvingtonian (Haile XVI) fossils differ from younger material
in two additional ways: a higher length: width ratio for the second and
third neural bones (Fig. 7) and a slightly more proximal site of rib
juncture with the second and third pleural bones (Fig. 8). These
characters do not exhibit allometry in Recent adult turtles, and there
is thus no reason to suspect it in Pleistocene populations. In these
respects Irvingtonian Deivochelys are morphologically intermediate
between the later Pleistocene and the Middle Pliocene turtles discussed
below. The near identity of the Blancan neural (UF 192^9) with that of

30

Table 2. Shell thickness index (STI) of fossil Deirochelys
from 16 Florida sites listed chronologically by
faunal periods.

Age and Site

STI

Age and Site

STI

Ari kareean

Rancholabrean, cont.

Thomas Farm

1.9

Bradenton

1.25

Hemp hi 1 1 ian

Kendrick

1.3

Love

1.6-2.1

Semi nol e Field

\.h

Mixson

1.8

Catal ina Gardens

1.3

Haile VI

1.9

Coleman IMC

1.3

Blancan

Waccasassa 1

1.1-1.3

Haile XV

1.5

Waccasassa V

1.1

1 rvington ian

Subrecent

Haile XVI

2.0-2.2

Warm Mineral Spring

1.15

Rancholabrean

N ichol ' s Hammock

0.95-1.05

Wal 1 Co. Pit

1.5-1.6

31

an Irvingtonian one (UF lOSSk) suggests that little shell evolution was
experienced between these periods.

The differences between modern and Upper Pliocene to Middle Pleisto-
cene Deiroohelys are real and might justify taxonomic distinction were
it not for the intermediate Ranchol abrean material. Such time-related
changes are, however, to be expected within a chronocllnal lineage,
as shown previously by Mil stead (I967) with Tevrapene. The modern
subspecies of D. veticulavia are distinguished by coloration and shell
shape (Schwartz, 1956) and consequently can not be compared to these
fossils. Furthermore, D. retioularia likely varied geographically
during the Pleistocene as it does now. For these reasons I refrain from
erecting subspecific epithets for any of the Pleistocene or Upper Plio-
cene fossils and simply refer them all to the species Deirochelys
retiaularia.

The existence of certain morphological differences, reflected in
carapacial osteology, of specimens referred above to D. veticulavia and
all earlier representatives of the genus (Figs. 7 and 8) is accentuated
by the absence of Late Hemphill ian fossils. This gap in a gradually
evolving lineage creates a convenient (though admittedly artificial)
point of division between morphologically distinct forms. I therefore
designate the turtle represented by the Middle Pliocene fossils as

Deivochelys cavvi new species

Etymology. Named in honor of Archie F. Carr for his extensive
contributions to our knowledge of Recent turtles and to herpetology in
general .

32

Holotype. UF 20908, a fragmented but nearly complete carapace
lacking only the nuchal bone, first neural bone, and anterior peripheral
bones (Fig. 13A); a partial plastron consisting of the left hyoplastron,
hypoplastron, and x iphi pi ast ron apparently represents the same individua:
(Fig. 13B).

Type locality and horizon. Alachua Clay, Love Bone Bed, near
Archer, Alachua County, Florida, Early Hemphill ian. Middle Pliocene.

Referred material . All from four Florida sites producing
Hemph i 1 1 ian faunas :

Mixson's Bone Bed: a fourth neural bone, UF 20890 (formerly Florida
Geological Survey V-2599) , assigned previously by 0. P. Hay (1916) to
Chvysemys aaelata: estimated CL 290, STI 1.8.

McGehee Farm: a complete (UF 1920^) and two partial (UF 2089I and UF
20903) nuchal bones - measurements of UF 19204: length 57.1, width
60.8, corresponding to a CL of approximately 263; right hypoplastron,
ninth right peripheral bone, and left and right x i ph i pi astral fragments
(UF 20899).

Haile VI: contiguous second neural bone fragment and proximal portion
of left second pleural bone, (UF 20887); estimated CL 253, STI 1.9;
contiguous pygal bone and eleventh left peripheral bone, (UF 6485a);
anterior end of third cervical vertebra (lacking zygapophyses) , UF
6485b (Fig. 14); five peripheral bones, UF 6485c; first neural bone,
(UF 6485d); seventeen pleural bone fragments, (UF 6485e) ; many other

33

elements and fragments from this site may represent either D. carri or
Chrysemys caelata (Chapter ill).

Love Bone Bed: Although excavation is incomplete, this deposit is already
the richest source of fossil deimohelijs known. At the time of this
writing over ^400 carapacial elements and half as many plastral elements
of Beivochelys have been removed. Other than the holotype, only two
sets of associated carapacial bones have been found (UF 2^100 and UF
20900, Fig. 15). The less water-worn carapacial elements display the
distinct scale-like sculpturing characteristic of the genus (Fig. 16).
Many elements represent turtles of exceptionally large size for Beivo-
chelys: the largest nuchal bone (UF 20906) measures 59.8 (length) x
61.8 (width). The average STI range is 1.6 to 2.1.

Diagnosis. Deivochelys aavri differs from D. veticularia in having
relatively narrower neural bones (mean length: width ratio of third
through fifth neural bones 0.8 to 0.9; Figs. 7, 13A) and a more proximal
site of emergence of the ribs from the pleural bones (Figs. 8, 15).
Elongation of cervical vertebrae and patterns of shell rugosity are
similar in these species, but the carapace of D. carri appears to be
relatively broader.

Shell rugosity and width of first vertebral scute of D. carri
are like those of Chrysemys caelata and C. williamsi , respectively, also
from the Florida Pliocene (Chapter III); nevertheless, other generic
characters distinguish these species from Z). carri. Neural bones of
B. carri are similar in shape to those of the Florida Pliocene Chrysemys
inflata (Weaver and Robertson, 1967), yet distinguished from them by

31^

absence of the pronounced keel and deeply excavated surface of the
latter.

Description. With the exception of the less developed character
suite previously alluded to, D. cavvi is, in most respects, similar to
B. veticulccpia. Nevertheless, many of the fossils indicate that the
former reached a greater size than B. reticulavia, perhaps as large as
320 mm CL, compared to approximately 250 mm CL today (Carr, 1952). The
shell of D. carri is about twice as thick as that of extant D. retioularia
but not unlike that of Blancan and Irvingtonian representatives of the
modern species (Table 2). Additionally, the reconstructed holotype
shell is relatively broad and flat compared to Recent chicken turtles.
In this respect, as well as in the flaring of the posterior peripheral
bones, D. carri is reminiscent of some members of the genus Chrysemys
and appears to have been more streamlined than D. reticularia. One
fairly constant difference between D. reticularia and D. carri is that
the anterior edge of the fourth vertebral scute (incised at the fifth
neural bone) of D. reticularia projects forward to form a sharp
anteriorly-directed V, whereas that of D. carri projects forward only
slightly (and more bluntly) or not at all (Fig. 1 3A) . The plastron of
V. carri, like that of D. reticularia, is narrow. The anal notch in the
plastron associated with the holotype of D. carri is twice as deep as
that of D. reticularia. There is no significant morphological variation
among D. carri from the four sites. Measurements and qualitative obser-
vations of all material from Halle VI, McGehee Farm, and Mixson's Bone
Bed fall within the range of variation of elements from the Love Bone
Bed.

35

Discussion. Veirochelys oarri is similar in most respects to its
presumed descendant D. veticulavia . The major differences are modifi-
cations associated with the further development of the specialized
elongate neck and head in D. reticularia. In this respect both D.
cavvi and B. veticulavia surely represent segments of a single chrono-
clinal lineage. The neural spines and dorsal rib heads of B. cavvi
are typical of the genus and only slightly more robust than those of
D. veticulavia. The single cervical vertebra (UF 6^85b) referable to
D. cavvi (Fig. U) is likewise slightly more robust than the correspond-
ing vertebra of D. veticulavia; additionally the posterolateral flanges
on the modern centrum, which must serve as muscle attachment surfaces,
are lacking in the fossil (the possibility of wear is unlikely).
Although it is impossible to determine accurately the length of the
Pliocene vertebra from the Haile VI fragment, it appears that the
characteristic cervical elongation and development of associated
modifications in Deivochelys had already approached present levels by
Middle Pliocene. Nevertheless, D. cavvV s narrower neural bones and
more proximal rib union with the pleural bones relative to D. veticulavia
imply a shorter free rib between the pleurals and vertebral column and
a correspondingly less developed set of cervical extensor muscles in
the former. A slightly shorter or less powerful neck in the Pliocene
species therefore seems likely. Certainly any future finds of Deivo-
chelys skull and cervical material in the Love Bone Bed would be
particularly valuable.

Although the Love Bone Bed provides us with an exceptionally
fine series of Deivochelys fossils, far older than any previously known

36

for the genus, we can trace the evolutionary record of this turtle back
still one step further - to the Miocene.

The Thomas Farm Deivochelys

The only emydine turtle previously recognized from the Florida
Miocene (Thomas Farm) is a species Chrysemys of uncertain status (Williams,
1953; Rose and Weaver, I966). In an effort to determine the relation-
ships of this turtle, I examined the holdings of the Flroida State
Museum for additional material. Among the elements retrieved were a
faintly sculptured neural bone (UF 219^+9) only slightly narrower than
those of D. carri , and the proximal fragment of a pleural bone (UF
21950) with a rib juncture scar too low for that of Chrysemys (Fig.
17)- Comparisons with Recent and fossil Deivochelys and Chrysemys ,
including "typical" Chrysemys elements from Thomas Farm, leave no doubt
that the two fossils represent Deiroohelys. Curvature of the scute
sulcus, relative length of the anterolateral borders, and extreme
lowness of the neural spine all indicate that the neural bone is a
fifth, while the relative proportions of the medial borders of the
pleural bone in addition to the position of the sulcus indicate that
it is probably the second pleural bone from the left side. As with
the Pliocene Deiroohelys , the shell is relatively thick (STI, 1.9).

In addition to the two fossils described above, I tentatively
refer to Deiroohelys the following elements from Thomas Farm: one
complete epiplastron (UF 21932) and the medial half of another (UF
21939), the posterior part of a right x i phi pi astron (UF 219^6), the
major part of an entoplastron (UF 219^2), and the proximal end of a

37

pleural bone (UF 21951). Additionally, one complete and two fragmentary
nuchal bones (MCZ 3^32; see Fig. 4 in Williams, 1953, and Fig. 2B in
Rose and Weaver, 1966), although probably representing Chrysemijs, may be
Deiroohelys. The width of the first vertebral scute and shape of the
nuchal scute are like those of both Deiroahelys and CJirysemys ovnata.

Both the shape of the neural bone (length: width ratio, 0.94,
Fig. 7) and the point of juncture of the rib with the pleural bone
(rib distance: pleural bone width ratio, Q.k], Fig. 8) indicate that, in
terms of cervical hypertrophy, the Thomas Farm Deiroahelys was even more
primitive (less specialized) than D. cavvi. Remains of the very low
neural spine fused to the neural bone confirm this. Hence, I believe
that the limited Thomas Farm material represents a turtle distinct from
B. cavvi. However, any taxonomic assignment of the Thomas Farm fossils
other than to genus must await additional and preferably associated
material. More important at present is that in the Thomas Farm Miocene
we find an important link in the gradual evolutionary sequence from a
generalized emydine ancestor (cf. Chvysemys) into the more specialized
d. cavvi and its highly specialized descendant, d. vetioulavia.

D i scuss ion

The material now available shows that the genus Deivochelys,
instead of being an evolutionary enigma, possesses possibly the most
complete evolutionary record of any modern turtle genus. Evolution of
Deivochelys has been by specialization of a generalized emydine stock
(presumably Chvysemys). The earliest fossils are, in fact, difficult
to distinguish from Chvysemys. We may estimate by extrapolation at

what point the two genera would be no longer d i st inct-- i . e. , the time
at which a generalized turtle began its Initial shift to a new adaptive
zone in response to selective pressure. The elongated neck (and pre-
sumably skull) as well as associated muscular (Shah, I963) and osteo-
logical modifications of Deivoohelys had already developed by Middle
Pliocene. This character suite is already conspicuous In hatchl ing
D. veticularia, so that phylogenetic recapitulation must occur very
early during ontogenetic development if It occurs at all. The divergence
from a more generalized aquatic emydine stock (moderately short neck,
long neural bones, weak hyoid apparatus, robust ribs emerging from very
near the proximal ends of pleural bones, limited trunk vertebral
musculature, and a relatively broad shell, as In the genus Chvysemys Br^A
some members of the Eocene genus Echmatemys) had certainly begun by the
Miocene. Extrapolations based on an average rate of evolution from such
a generalized ancestor suggest an 01 igocene origin of the genus (Fig.
18). This character suite almost certainly evolved as a peculiar
trophic structure; Deivoohelys utilizes a "pharyngeal" method of feed-
ing (Bramble, 1973) for capturing prey capable of quick movements (pri-
marily aquatic arthropods). Arguments such as those of Webb and
Johnson (1972), In which cervical elongation Is held to represent a
thermoregulatory device, seem at most of secondary significance in
this case, particularly in light of the hypoertrophi ed hyold skeleton.

The thick shell of D. cavvi and the Thomas Farm deivoohelys, as
well as of Blancan and Irvingtonian B. vetioulavia (Table 2), suggests
that until Late ?\&\stoc&n&, Deivoohelys was a moderately thick-shelled
turtle. Pleistocene reduction in weight and volume of the shell may

39

have allowed faster pursuit and increased maneuverability necessary for
capturing fast-moving prey (author's unpublished data) on which Deiro-
ohelys had come to specialize. Loss of armor (if the thick shell served
this purpose) may have been offset by crypsis and behavioral immobility
(unpublished observations). In addition to changes in shell thickness,
general reduction in body size, accompanied by relative elongation and
heightening of the shell, seems to have occurred from at least Hemphillian
to Rancholabrean times.

Rel at ionshi ps

Baur (1889) was the first to hypothesize a close relationship be-
tween Emydoidea and Deirochelys on the basis of similar skull and rib
specialization. Although Carr (1952) believed the similarity between
Emys (= Emydoidea) hlandingii and D. veticularia to be "purely
fortuitous," most subsequent workers supported Baur's idea. Bramble
(197^) summarizes the situation:

Williams (in Loveridge and Williams, 1957) presented a
forceful case for a relationship between Emydoidea and
Deirochelys. Although DeivooheZys possesses no plastral
hinge and on many points of shell morphology closely
approaches certain members of the genus Chrysemys
(McDowell, 196^), it does, as Williams noted, share with
Emydoidea a number of specializations of the skull,
cervical vertebrae and neck musculature. On these
grounds Williams suggested that Emydoidea was a derivative
of Deirochelys and only convergent with Emys. This view
has been widely adopted by later workers (Tinkle, 1962;
McDowell, 1964; Zug, I966; Pritchard, 1967; Milstead,
1969; Ernst and Barbour, 1972), some of whom (Tinkle,
1962; Zug, 1966) have presented additional evidence In
support of it. McDowell (1964: 275) found no 'signifi-
cant cranial differences between Deirochelys and Emydoidea^
and accordingly placed both genera in a Deirochelys Complex
within the Emydinae. (p. 12h)

ko

However, Bramble's (197^) study of shell kinesis and other osteological
and myological characters indicates instead that Emydoidea is a "close
phyletic associate of 5'mys and Tepi^opene" as well as of Clenmys (the
four genera comprising the Ctemmys Complex), and that these genera may
be distinguished as a group from Deivochelys and McDowell's (1964)
Chrysemys Complex. Waagen (1972) formed an identical opinion from
his analysis of musk glands in Recent turtles. On the basis of fossils
discussed in this paper I agree with the conclusions of Waagen (1972)
and Bramble (197^) that Deiroahelys shares a close relationship with
the genus Chrysemys, and that similarities hetvieen Emydoidea and Deiro-
ahelys are "undoubtedly the result of convergent feeding system"
(Bramble, 197't). In fact, most of the modifications used to
substantiate a close relationship between Deivochelys and Emydoidea
(elongated ventre 1 1 y-bowed free ribs, widened neural bones, elongated
cervical vertebrae, and a greatly hypertrophied cervical musculature)
are also present in the totally unrelated (at least at the familial
level) cryptodire genus Chelydra as well as the pleurodire genus
Chelys. They are, moreover, all modifications associated with the
pharyngeal method of feeding (Bramble, 1973) employed by these turtles.
Hence, the taxonomic use of this particular character suite, so clearly
convergent among members of three distinct families, should be treated
cautiously in attempts to determine i ntrafami 1 ia 1 relationships. This
paper has presented evidence of the gradual development of these
adaptations as a unit of functional morphology (Wilson, 1975) within
one of these phyletic lines.

Pleistocene and Late Pliocene fossils of Emydoidea, which are
clearly referable to the modern species E. blandingii (Taylor, 19^*3;

^1

Preston and McCoy, 1970, show no special resemblances to Late Tertiary
Deirochelys , other than the convergent character set already discussed,
and hence do not support a theory of their divergent evolution. Neither
the fossil records nor the present distributions (Carr, 1952; Preston
and McCoy, 1971; Zug and Schwartz, 1971; McCoy, 1973; Jackson and Kaye,
197^) give any indication that the two genera were ever sympatric,
although the southern extension of the range of Emydoidea in the Late
Pleistocene (Jackson and Kaye, 197^*) closely approaches the present
northern limit of Deirochelys in Mississippi. Further ecological
studies might help to determine if this allopatric relationship reflects
a Gause-type competitive relationship or a difference in thermal re-
qu i rements .

Distribution and Paleoecology

The genus Deirochelys is endemic to the southeastern United
States, and it is therefore not surprising that the first extensive
evidence of its fossil history should be from Florida. All vertebrate
fossil sites known to contain Deirochelys (Fig. 3) occur within the
range of the modern subspecies D. reticularia chrysea or its zone of
intergradat ion with D. r. reticularia (Schwartz, 1956; Zug and
Schwartz, 1971).

Deirochelys reticularia usually inhabits quiet, shallow bodies
of freshwater throughout its range although it occasionally enters the
quieter portions of streams (Pope^ 1939; R- Webb, 1950; Carr, 1952;
Schwartz, 1956; Campbell, I969) and perhaps rarely saltwater (Neill,
19^*8; Martof, I963). Personal observations in north-central Florida

k2

indicate that the densest populations of Deivochelys occur in shallow
(less than one meter) ponds with abundant basking logs, emergent bushes
(e.g., Cephalanthus), and an extensive Lenma-Wolffiella surface mat.
From a structural standpoint, the relatively short limbs, long nuchal
scute underlap, and absence of streamlining (as compared to a lotic
form such as Chrysemys conoinna) reflect its evolution as a quiet-
water form. The turtle also shows a proclivity for overland wanderinc
(Neill, 19^*8; Carr, 1952; Gibbons, I969, 1970). Its typical association
with the Southeastern Coastal Plain (Mount, 1972; Mount and Folkerts,
1968) implies adaptation to a warm temperate climate. The presence of
Deivochelys and associated fauna {he-pisosteus, Amia, Alligator, Chry-
semys aaelata {Chapter III), Trionyx cf. T. ferox] in Hemphillian sites
thus indicates the existence of quiet freshwater (e.g., sinkhole
ponds or sluggish streams) and a warm, equable climate in the Florida
Midd 1 e PI iocene.

Even In the most favorable habitats Deivochelys today rarely
reaches densities comparable to those of sympatric emydine turtles (e.g.,
Chrysemys nelsoni, C. flovidana, C. scvipta) . This relationship appears
to hold also in the Pliocene; in the only Pliocene deposit containing
large numbers of Deivochelys (Love Bone Bed), Chrysemys caelata elements
outnumber those of D. carri approximately four to one. In what presumably
was a suboptimal habitat for Deirochelys at McGehee Farm the ratio is
even more disparate. This indicates that populations of Deirochelys
may be more restricted by limiting factors than are other emydines.

All fossil records for Deirochelys from sites near the present
coastline of Florida (Fig. 3) are either Subrecent or Late Ranchol abrean.

^3

All other sites except those in the Waccassassa River are in presently
wel 1 -drained localities 21 to 37 m above present sea level; these in-
clude all sites assigned to the Hemphillian, I rv ington ian , Blancan,
and early Rancholabrean periods.

Webb and Tessman (I968) have presented vertebrate faunal evidence
supporting conclusions based on physiographic evidence (Alt and Brooks,
196^; Alt, 1967) that sea level dropped and rose again as much as 30
meters during Hemphillian (middle Pliocene) time. McGehee Farm (early
Hemphillian) was thus very near the Pliocene coastal shoreline during
its time of deposition and its fauna clearly reflects an estuarine
influence, although nearby Mixson's Bone Bed, which occurs at the same
elevation, does not (Webb, 1964; Webb and Tessman, I968). Additionally,
the Late Pliocene and Middle Pleistocene interglacial deposits contain-
ing Deivochelys were much nearer to coastal shorelines during deposition
than they are today. It seems probable that since at least the Plio-
cene Deivochelys has been associated primarily with lowland habitat,
as was the Pleistocene box turtle subspecies Tevrapene cavolitia putnami
in Florida (Auffenberg, 1958). Distribution of these turtles in the
Florida peninsula and along the Gulf coast must have fluctuated with
the advance and retreat of the Pleistocene sea. The proclivity of the
genus for overland wandering has probably been instrumental in maintain-
ing or reestablishing inland populations at higher elevations in the
abundant "perched" lakes (bodies of water which are completely above
the piezometric surface and sometimes subject to spontaneous drainage)
common throughout much of the peninsula today. The present inland
populations may be relicts of higher sea levels or terrestrially-
reestablished populations.

Figure 3- Fossil sites in peninsular Florida containing Deiroohelys.
Site ages are given in Appendix.

9. Semi nole Field

1 0. Catal i na Gardens

1 1 . Bradenton

12. Warm Mineral Springs

13- NIchol's Hammock

]k. Reddick I IC

15. Thomas Farm

16. Vero

1

McGehee Farm

2

Ha i le si tes

3

Love Bone Bed

h

Wal 1 Company P i t

5

Mixson's Bone Bed

6

Kendrick lA

7

Waccasassa River sites

8

Col eman IMC

'f5

Figure k. Third neural bones of Chrysemys floridana (A) and

Deivoahelys vetiaularia (B) ; note greater width and
characteristic sculpturing of latter.

Figure 5- Frontal aspects of third pleural bones of Chvysemys

aoncinna (A) and Deivoahelys vetiaularia (B) , showing
dorsal ribs.

if?

/

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Figure 7. Length: width ratios of second through sixth neural

bones of Recent (closed circles), Irvingtonian (stars),
Hemphillian (triangles - Love; square - Haile VI;
asterisk - Mixson's), and Arikareean (open circle)
Deiroohelys. Dice - Leraas diagrams depict mean,
range, and two standard errors; numbers above and below
bars represent sample sizes.

51

1.0-1

10

10

1
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X

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I—
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NEURAL NUMBER

Figure 8. Rib distance: pleural bone width ratios for Recent,
Pleistocene, and Pliocene Deiroahelys; all symbols
as in Fig. 7-

53

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X

a .8

<

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3 4 5

PLEURAL NUMBER

6

Figure 9. Nuchal (UF 16271) and three neural bones (TRO 101-103)

of Rancholabrean Deivoohelys reticularia from Waccasassa
River V and I, respectively.

Figure 10. Distinctly sculptured nuchal bone (UF 9292) and sixth
neural bone (UF 19250) of Deirochelys reticularia
from Kendrick lA.

55

^^^^R^, «Pp

w

Figure 11. Dorsal (A) and ventral (B) surfaces of carapace fragment
(UF 20888) of Irvingtonian Deirochelys retiaularia
(Haile XVl). Note sculpturing, neural bone width,
and rib junctures.

Figure 12. Fifth neural bone (A, UF 192^9) and nuchal bone fragment
(B, UF 19168), of Blancan Deirochelys retiaularia (Haile
XV), showing broad nuchal scute underlap.

57

• s.

%■

V^'

•f\

Figure 13A. Beirochelys carri holotype, UF 20908, dorsal aspect
of carapace. Hatched areas missing from fossil.

59

Figure 13B. Deivochelys oarvi holotype, UF 20908, ventral aspect of
plastron. Hatched areas missing from fossil.

61

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63

Figure 16. A distinctly sculptured nuchal bone (A) and posterior
peripheral bone (B) of Deiroohelys oarri from the
Love Bone Bed (x 1.15).

Figure 17. Beirochelys fossils from the Thomas Farm Miocene
(X 2.25). (A) Neural bone, (B) visceral surface
of pleural bone fragment showing rib juncture scar.

65

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CHAPTER I I I
THE STATUS OF THE PLIOCENE TURTLES

CHRYSEMYS CAELATA (HAY) AND CHRYSEMYS CARRI ROSE AND WEAVER

Three non- Trachemys species of Chrysemys (sensu McDowell, 196^)
have been described from the Pliocene ofRorida. Hay (I908) described
C. caelata, largely on the basis of shell sculpturing, from MLxson's
Bone Bed," Levy County. Hay considered this site Pleistocene in age
although it had previously been recognized as Pliocene (Dall and Harris,
1892; Leidy and Lucas, I896) and was so reassigned by Simpson in I929.
Rose and Weaver (I966) examined shells of Chrysemys from McGehee Farm
in adjacent Alachua County and described both a smooth-shelled species
{C. williamsi) and a rugose species {C. carri) yet made no reference to
C. caelata. Both sites are Pliocene deposits within the Alachua
Formation (Simpson, 1929a; Rose and Weaver, I966; Hirschfeld and Webb,
1968). The occurrence of two rough-shelled species in approximately
equivalent strata only 3k km apart prompted me to investigate their
taxonomic status. All specimens are in the collections of the U.S.
National Museum (USNM) , Florida State Museum (UF), and Florida
Geological Survey (FGS).

"Uncertainty surrounds Hay's designation of the type locality of C.
caelata, as it does much of the early Mixson material (Simpson, 1929a).
In conjunction with the original description. Hay (I908) gave the
locality as '"Mason's bone bed,' somewhere in Levy County, Florida,"
but later (I9I6) referred the site only to "somewhere in Levy County
Florida," The data with the USNM specimens read "Levy County, Florida
1885, L. C. Johnson." As this is the period when Johnson and other
representatives of the U.S. Geological Survey were originally
investigating Mixson's Bone Bed (Simpson, 1929a), and as the material
exhibits the same condition of preservation as known Mixson material
I suggest that "Mason's" is a liberal orthographic interpretation of
Mixson' s."

68

69

Taxonomic Considerations

Chrysemys caelata was described by Hay (1908) on the basis of 11
unassociated elements; of these he considered 10 (USNM 2508) as probably
representing one large individual and a single pleural (USNM 6064) a
smaller specimen. The nuchal bone was designated as the type. My
examination of this material reveals that probably no more than two bones
represent any single individual. However, the entire series appears to
represent one species. The two posterior peripherals to which Hay
(1908) referred are a tenth and eleventh from the right side. In his
original description (I908) he wrongly referred to the seventh right
peripheral as a third left, but corrected this error in 1916. As Hay
gives adequate measurements and detailed accounts of the sculpturing on
most of the bones, a redescript ion of the material is unnecessary.

Hay (1908) placed great emphasis on the characteristic sculpturing
of the shell of C. caelata, which he said "resembles that of Traahemys
saripta" (= Chrysemys) . The sculpturing bears an even stronger
resemblance to that of C. nelsoni, which, 1 i l<e saripta, occurs in
Florida today. Having only limited material from which to describe
the sculpturing. Hay did not appreciate the range of i ntraspeci f ic
variation to which this character is subject. Other specified diagnostic
characters include a wel 1 -developed epiplastral lip and absence of
nothces along the posterior carapace edge.

Rose and Weaver (1966) described Chrysemys oarri from a series of
incomplete shells (holotype UF 9^27 and nine paratypes). They diagnosed
it as "a species of Chrysemys with a rugose carapace and plastron, a
slight median posterior keel, long nuchal scute underlap..., moderate

70

gular scute overlap..., un-notched peripherals," large epiplastral lip,
"and a clearly notched and rectangular pygal bone."

I have examined and compared the type series of both C. oarri
(except UF 1 1 083 which could not be located) and C. caelata. Patterns of
surface rugosity and scutellation of the individual elements of C. caelata
are well within the range of and often virtually identical to sculpturing
and scutellation patterns of corresponding elements of C. oarri (Figs. I9
and 20). Measurements of the type nuchal bones show no significant
differences in proportions (Table 3). The long nuchal scute underlap
of C. carri, which distinguishes this turtle from C. williaxnsi and C.
concinna (Rose and Weaver, I966), is also evident in the type of C.
caelata (Fig. I9, D and E) . Examination of more than 100 nuchal bones
of C. oarri reveals that the length/width ratio of the nuchal scute
underlap varies from 1.0 to 2.3- The ratio for the type of C. caelata
is 1.0, within the limits of variation in the McGehee series. Sulci on
the dorsal surface of the caelata nuchal are aberrant (Fig. I9A); these
measurements are of little value. The moderate gular scute overlap of
C. oarri, a character stressed by Rose and Weaver (I966) as highly
diagnostic, is not significantly different from that on the type
epiplastron of C. caelata (Fig. 20, A and C). The epiplastral lip is
pronounced in both C. oarri and C. caelata (Fig. 20), although within
the large McGehee series the shape and size of this lip are clearly
variable. In both C. caelata and C. oarri the peripherals, and hence
the carapacial margins, are un-notched. Furthermore, in both descriptions
the authors characterize the posterior peripherals as horizontally
flared (i.e., with a concave upper surface). Finally, all of the

71

Table 3- Maximum measurements (mm) of holotype
nuchal bones of Chrysemys caelata and
C. oarvi.

caelata cavvi-

length A6.6 hh.k

width 53.3 52.0

r'r'°' 23.3 23.0

border

72

elements assigned to C. oaelata represent turtles within the size range

of C. carri (largest plastron in McGehee series, 295 mm; estimated carapace

1 ength, 338 mm) .

I am unable to compare the remaining diagnostic characters of C.
oarri--the slight median posterior keel and the notched rectangular pygal
bone--with C. caelata as Hay's (1908) type series includes neither neurals
nor pygal. Hay (1916) later erroneously assigned the neural (FGS \/-2599 =
olf 3^25) of a Deirochelys to C. caelata; the impact of this error was
discussed in Chapter II.

There appear to be no significant morphological differences between
C. oaelata and C. oavri. Furthermore, considering the geographic proximity
of the type localities (3^ km) and the approximate strat igraphi c
equivalence (Webb, \%k\ Hirschfeld and Webb, 1968) of the horizons, the
names undoubtedly refer to the same species. Chvysemys carri Rose and
Weaver is therefore a synonym of Chrysemys caelata (Hay).

Rel at ionships

Patterns of shell sculpture, scutellation and shell morphology of
C. caelata are similar to those of C. nelsoni; the two species are surely
closely related if not synonymous. Nevertheless, they may usually be
distinguished by the shapes of the entoplastron and first suprapygal
(Fig. 21). In addition differences in the ratios of maximum gular scute
length/epiplastral lip width {oaelata x, 0.66; nelsoni x, 0.80) and
posterior width of first suprapygal /greatest width of second suprapygal
{oaelata x, 0.63; nelsoni x, Q.kk) are significant (Student's t-test,
p < 0.025). Also, the pygal bone of C. caelata is more truncate, less

73

deeply notched, and usually less deeply overlapped by the fifth vertebral
scute than that of C. netsoni.

Rose and Weaver (I966) assigned two mandibles (UF II086 and UF IIO95)
from McGehee Farm to C. oaelata. Based on its flattened verntral surface,
which is nearly continuous with the scar marking the insertion on the
dentary of the M. occ ip i to-squamoso-maxi 1 lar i s [(= Temporalis of
Wiedemann, and M. temporalis of Bojanus, Stannius, Cuvier, and Owen)
Hoffman, I89O], mandible UF 11095 is similar to that of C. nelsoni and
hence may represent C. aaelata. There are no indications of the serrated
cutting edge, bicuspid notching, or broad alveolar surface characteristic
of jaws of C. nelsoni. However, mandible UF IIO86 is less flattened
ventral ly, the muscle scar does not come close to reaching the ventral
surface, and the entire jaw is foreshortened (hence, wider) relative to
C. nelsoni; these conditions are similar to those of C. ooncinna (as well
as C. floridana) and the jaw likely represents its predecessor, C.
williamsi. For the present, as no skull material positively referable to
C. oaelata is known, this species must be considered specifically distinct
from C. nelsoni.

Further study is also needed to clarify the relationship of C.
oaelata with other Pliocene and Early Pleistocene Chrysemys, particularly
C. idahoensis from Blancan beds in Idaho (Gilmore, I933; Rose and Weaver,
1966) and C. hilUiof the Kansas Lower Pliocene. The latter has been
associated by most authors with the Traohemys line (Cope, I878; Hay,
1908; Adler, 1968; F. Rose, pers. comm.), and certain characters (e.g.,
notching of pyga 1 and peripheral bones) would seem to distinguish it
from C. oaelata.

Ih

Discussion

Chrysemys oaelata is now known from a large series of nearly complete
shells from McGehee Farm in addition to the few original elements from
Mixson's Bone Bed. The characteristics described by Rose and Weaver
(1966) may be added to those listed by Hay (I908) to give us an improved
definition of this species. Other than these two descriptions, C. caelata
has been mentioned few times in the literature. Of the 12 additional
Mixson elements Hay (1916) assigned to this species, at least the neural
and probably the epiplastron represent De-iroahelys . Four of these,
including the epiplastron (which, however, is pictured), must tentatively
be considered lost. I have examined the remainder and, except for the
neural, agree with Hay's assignment (although the peripheral he refers to
as the second left is actually a first left). Gilmore's recognition of
C. caelata from Melbourne, Florida (Hay, 1923, 1927), which Hay believed
to be Aftonian (Late Blancan) but now generally considered Rancholabrean
(Hibbard et al., I966; Webb, 197^), is extremely doubtful. I have seen
only C. soripta from this site. All other references to C. caelata
(Auffenberg, 1955, 1963; Coin and Auffenberg, I955) refer to a series
of elements from Ha i 1 e Vl, another Florida Pliocene site only 3 i<m
east of McGehee Farm. Many of these elements (a neural and the proximal
ends of several pleurals) actually represent the genus Deivoohelys
(Chapter 11). Allocation of the remaining fragments (mostly peripherals
and distal ends of pleurals) is difficult; tentatively I consider at
least some of them to represent C. caelata. Recent excavation of a
newly discovered Pliocene site (Love Bone Bed) at Archer, Alachua County,
Florida (29°33'N, 82°3rW; sec. 9, TllS, RI8E) has yielded large quantities

75

of turtle material, much of which can be definitely assigned to C. caelata;
to date, two partial shells (UF20869 and 20870) as well as numerous
unassociated elements representing this species have been removed.

Ckrysermjs caelata, then, is a rugose Chrysemys presently known from
four PI iocene sites ;encompassing a total area of only kl square kilometers
in adjacent Alachua and Levy Counties, Florida. Recent workers (Auffenberg,
1963; Hirschfeld and Webb, 1 968 ; Webb, I969 and pers. comm.) have
assigned all four sites to the Alachua Formation. Although the "formation"
is time-transgressive, including sediments ranging in age from early
Miocene through Recent, fossils representing distinct faunas within it
are often unmixed (Simpson, 1930; Cooke, 19^5; Vernon, I95I; Auffenberg,
1963; Puri and Vernon, 1964; Hirschfeld and Webb, I968). I therefore
conclude that Chrysemys caelata is indicative of eiarly Hemphill ian
faunas (Hirschfeld and Webb, I968; Webb, I969) of the Alachua Formation.
Morphologically, C. caelata appears to be ancestral to C. nelsoni,
a relatively common turtle of both Pleistocene and Recent Florida. Like
nelsoni, caelata was probably characteristic of still or slow-moving
water. Likewise, caelata' s coeval at McGehee Farm, C. williamsi (Rose
and Weaver, I966), appears, on the basis of shell morphology, to be the
Pliocene forerunner of C. concinna, a stream- i nhab i tant (Crenshaw, 1955)
of Pleistocene and Recent Florida. These two lines [floridana- concinna
species group and rubriventris species group, including C. nelsoni)
within the subgenus Pseudemys (sensu McDowell, 1964) were therefore
distinct in north peninsular Florida by Middle Pliocene. Nevertheless,
Crenshaw(l955, 1965) indicates that in rare instances in the southeastern
United States reproductive isolation of the two groups has either

76

partially broken down or not yet fully developed. That C. caelata and
C. williamsi were found in separate concentrations within the McGehee
deposit (Rose and Weaver, I966) suggests that although sympatric they
may have been predominantly allotopic (as are C. nelsoni and C. conainna
today in this region). Sed imentology and associated faunas in the sa
deposits (Webb. 1964; Hirschfeld and Webb. I968) support this hypoth

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Figure 21. Ventral surfaces of entoplastra (A, C) and dorsal
surfaces of suprapygal bones (B, D) of Chrysemys
nelsoni (A, B) and C. oaelata (C, D) .

82

B

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D

\

CHAPTER IV

A REEXAMINATION OF THE CERYSEMYS SCRIPTA GROUP BASED ON

FOSSIL EVIDENCE

The systematic status and relationships of Chvysemys soripta and
its close relatives have been a major center of controversy among turtle
evolutionists. Most early workers (Agassiz, 1857; Gray, I87O; Hay, I908;
Gilmore, 1933) assigned the C. scripta complex full generic standing as
the genus Trachemys , although Boulenger (I889) included it in Chrysemys.
Subsequent workers (Carr, 1952; Williams, 1956; Loveridge and Williams,
1957) incorporated the group into the genus Pseudemys (as had Cope, I878)
but made few statements about intrageneric relationships above the
species level. It was not until 1964 when McDowell considered Pseudemys
and Chrysemys {sensu striata) congeneric that subgenera were formally
recognized. The subgenus Trachemys included all members of the C. scripta
complex; the subgenus Pseudemys included two series of turtles--the
floridana series (C. floridana and C. conainna) and the rubriventris
series (C. rubriventris, C. alahamensis and C. nelsoni) --both more
closely related to each other than either is to Trachemys; finally, the
type species of the genus, C. picta, was considered a third distinct
subgenus, Chrysemys.

Weaver and Rose (1967) examined the ideas of McDowell (1964) using
fossil and extant material and concluded that his subgenera were invalid.
They developed a new phylogeny for the genus in which they cons idered the
North American C. scripta group to be more closely related to the C.
rubriventris complex, and the West Indian, Mexican, Central and South

83

8^

American turtles previously considered races of C. scripta to be more
closely related to C. ftoridana and C. concinna. Their failure to
recognize the importance of convergence of specific adaptations, as well
as the false premises on which they delineated "ancestral characters,"
leave their conclusions suspect.

One of the major drawbacks to a vertical study of the C. scripta
complex has been the absence of skulls of extinct forms; in fact, only
two fossil emydid skulls from all of North America have been previously
reported (Hay, 1 908 ; Gilmore, 1933), and the identities of these are
ambiguous. McDowell's (1964) conclusions, drawn almost entirely from
cranial characters, have therefore been nearly impossible to apply to
fossil forms, the taxonomy of which has necessarily been based almost
exclusively on shell osteology. In this paper I report previously
unrecognized skull material from the Florida Pliocene which casts new
light on some of these problems. Furthermore, only very limited attempts
have been made to relate fossils from Florida to those from the Great
Plains; this must be done if pal eontolog ical species are to have
biological meaning. My purpose, therefore, is not to revise the genus
again, but to analyze all available fossils to point out problems with
some of the earlier schemes, and to reinterpret intrageneric relationships
accordingly. Of primary interest here is the relationship of the C.
scripta complex to other members of the genus. The term "North American
C. scri-pta,*' as used in this paper, includes only those turtles occurring
in the continental United States. All fossils, unless otherwise noted,
are in the vertebrate paleontology collection of the Florida State
Museum (UF) .

85

Tvachemiis In the Pleistocene

Probably due to their abundance in the Pleistocene of Florida and
Texas and the ease with which they may be recognized, fossils of the C.
scripta group (i.e., Traohemys) have been known longer and studied more
extensively than those of most other southeastern emydid turtles. Hay
(1908, I9I6) recognized eight extinct species from Pleistocene deposits
in Florida and Texas that he assigned to this group: Traohemys euglypha
(Leidy), T. saulpta Hay I908, T. ? jarmani Hay I9O8, T. petrolei
(Leidy), T. bisomata (Cope), T. tvulla Hay I908, T. ? delioata Hay
1916 and T. ? nuohooarinata Hay I9I6. Weaver and Robertson (I967)
correctly placed six of these names in synonymy with C. saripta and
incorporated them, as well as other Florida Rancholabrean material, in
their new combination C. s. petrolei. The remaining two names represent

fossils incorrectly assigned to Traohemys: T. nuohooarinata = Terrapene

Carolina (Auffenberg, 1958) and Traohemys jarmani = C. nelsoni (Chapter
II). The only other Traohemys recognized by Hay was T. hillii (Cope)

from the Pliocene Loup Fork beds of Kansas; it is discussed further

below.

Because of intraspeci f ic variation within Recent, Rancholabrean,
and irvingtonian C. soripta, the utility of C. s. petrolei as a reliable
stratigraphic tool in Florida is meager. Justification for giving the
Rancholabrean fossils separate taxonomic status must be questioned.
Weaver and Robertson (I967) distinguish C. s. petrolei from all other
C. soripta by only two characters: its larger average size and greater
carapacial rugosity. They admit, however, that these are "minor
distinctions." They also state that "the extensive rugosity and

sculpturing of the RanchoJabrean fossils is often present in large, extant
specimens of C. s. saripta." Furthermore, they add that "an additional
series of fossils from Ichatuckenee Springs" shows "a size gradation from
typically large Rancholabrean nuchals to smaller ones which, in the absence
of mineralization, are indistinguishable from those of extant C. s.
scripta" (italics mine).

Neither of the two characters used to diagnose C. s. petrolei is
reliable. Although the shells of Rancholabrean C. saripta are often
more rugose than their modern counterparts, the character is subject to
extreme variability in both temporal groups. It is not uncommon to find,
in peninsular Florida, living C. saripta whose shells are more rugose and
more deeply insculpted than those of many fossil C. saripta.

The second and chief character by which Weaver and Robertson (196?)
define C. s. petrolei- \arger average size than extant C. saHptaseems
to me insufficient to serve alone as the basis for a separate taxon.
The larger average size of turtles in the Pleistocene versus those today
is not unique to C. saripta. It can be documented not only in other
species of Chrysemys in Florida but also in most other genera; e.g.,
Deiroahelys (Chapter II). Graptemys (Chapter I), and Terrapene (Auffenberg.
1958). Many reasons can be speculated to account for larger size in the
Pleistocene: climatic differences as they affect heat loss and retention
by poikilotherms; size-selective predation by man or other predators; and,
nutritional differences in diet, etc. Body size is a complex phenomenon
and should not be used as the sole criterion for establishing additional
taxa.

The designation of a temporal subspecies must be made with extreme
caution (see Mayr, I969). Although the concepts of temporal and geographic

87

subspecies are not necessarily equivalent, they must nonetheless be
compatible when applied to one species. The designation of a temporal
subspecies that might in itself encompass more than one geographic
subspecies is more apt to cause confusion than to increase understanding.
This is precisely the case with C. s. petrolei, as pointed out previously
by Preston (1971). Two distinct subspecies occupy the purported range
of C. s. petrolei (Florida to Atascosa County, Texas) today: C. s.
elegans in the west and C. s. saripta in the east. The possibility
certainly exists that more than one race of C. saripta occupied this
region during late Pleistocene, so that C. s. petrolei in Texas may have
been subspeci f ical ly distinct from C. s. petrolei in Florida. Essentially
the same problem arose when Preston (I966, 1971) recognized C. s.
hisornata (by which he meant C. s. elegans-] ike turtles from the
Irvingtonian mammalian age) from both Florida and Texas.

It is unfortunate that the diagnoses of the modern subspecies of
C. scripta rely almost entirely upon color pattern, as they thus cannot
be compared directly with the fossils. The osteological characters used
by Preston (1966) to distinguish these forms have some val ue--part icular ly
the development of the middorsal i<eel and the relief of the nuchal
lamina--though i ntrasubspec i f ic variation is too great to consider them
infal i bl e.

Interestingly, C. scripta from Irvingtonian deposits in Florida
and Texas appear to differ osteolog ical ly in the same way that the
subspecies C. s. saripta and C. s. elegans differ in these regions today.
Thus, a nearly complete shell (MUVP 45^6) from the early Irvingtonian
Seymour Formation, Burnette Ranch, Knox County, Texas, lacks a pronounced

middorsal keel and has a relatively flat nuchal scute and low profile.
A partial shell (UF 2l802) from Coleman MA, Sumter County, and a series
of elements from Haile XV I , Alachu£< County--both Irvingtonian deposits in
Flor ida--d i spl ay the raised nuchal scute, pronounced middorsal keel, and
slightly higher profile characteristic of C. s. scripta. It appears,
therefore, that these two modern subspecies became established no later
than early Pleistocene. Any scheme that assigns these fossils subspecific
standing distinct from modern forms seems to me biologically unrealistic
and an artifact of choosing one's own lifetime as a significant point of
reference in geologic time.

I suggest, as implied by Preston (1971), that until we achieve a
better understanding of the C. saripta group (possibly through the
discovery of more fossils), the recognition of fossil subspecies is
unwarranted and can only lead to further confusion. Fossils resembling
C. s. elegans or C. s. scripta should be referred to the species and their
apparent affinities with modern subspecies discussed, but assignment of
temporal subspecific names is presently premature.

Pleistocene fossils of C. saripta provide us with information on
the species' former distribution and the occurrence of subspecies.
However, for knowledge of the evolution of Trachemys we must look back
to at least the Pliocene.

Trachemys in the Upper Pliocene

Systemat ics

Weaver and Robertson (1967) described Chrysemys platymarginata as
a member of the Trachemys group from Haile XVA, Alachua County, Florida.

Although the fauna of this site was then thought to be Irvingtonian
(Pleistocene), Robertson (1976) has since reinterpreted it as Blancan
(latest Pliocene). Other peninsular Florida sites of Blancan age also
contain C. pZatymarginata (Weaver and Robertson, 1967). Based on shell
morphology (doubly- toothed peripheral bones, extensive gular scute
overlap and nuchal scute underlap, highly sculptured nuchal bone, and
well developed median keel on the carapace), Weaver and Robertson
properly assigned C. pZatymarginata to the C. scripta complex (subgenus
Traohemys) . They believed no skull material of C. pZatymarginata was
available. However, a small box of cranial fragments from Haile XVA,
collected in 1964 by S. D. Webb, J. Robertson, and R. Allen, contains
parts of the skulls of this species, and a chelydrid and trionychid.
The fragmentary materia] was reassembled and compared to literature
descriptions (Hay, I908; Gilmore, 1933; McDowell, 1964; Weaver and
Robertson, I967) and Recent specimens. Much of the cranial anatomy of
the fossil emydid can be observed from three partial skulls (UF 21888,
21892, and 21963); UF 21888 includes both dentaries as well. Unassociated
fragments (UF23920 and 23921) from several other skulls are also
available. Since other emydids (e.g., Chrysemys ooncinna and DeivooheZys)
are also present in the Haile XVA fauna, the emydid skull fragments must
be examined closely before specific assignment is made.

McDowell (1964) diagnoses the genus Chrysemys by the following
cranial characters: "triturating surface of maxilla with sharply defined
middle ridge; anterior edge of inferior process of parietal thin;
posterior end of pterygoid usually not in contact with exocc i p i tal ."
Examination of the Haile XVA skulls confirms their identity as Chrysemys
as defined by McDowell (1964).

90

Additionally, according to the criteria set forth by McDowell (196^.)
and modified by Weaver and Rose (I967). the skulls are clearly associated
with the Tvaahenys line within the genus. McDowell characterizes the
subgenus as follows: ventral surfaces of dentary relatively rounded,
middle ridge of upper triturating surface lacking an anterior cusp,
maxilla not sutured to quadratojugal (= McDowell's squamosal), pterygoid
extending back near the exoccipital, and crista praetemporal is heavier
than in other Chrysemys. The Ha i 1 e XVA skulls are clearly assignable
to the TTaohemys line within the genus Chvysemys and may thus be confidently
referred to C. platymarginata , the shell of which also reflects its
Trachemys affinities. Two other cranial characters that I find consistent
with extant Trachemys are the recessed vomer, which does not participate
in the alveolar surface (unlike the C. rubriventris complex), and the
broad pterygoids (O.3I to 0.32 times skull width, as compared to 0.23 to
0.28 for species of the C. rubriventris group and 0.32 to O.38 for C.
soripta; Fig. 22A. A symphysial ridge on the mandibular alveolar surface

appears to be consistently absent or inconspicuous in all living and
fossil Trachemys. Finally, the posterolateral region of the dentary of

C. platymarginata, as in C. scripta, rises abruptly to meet a relatively

higher coronoid bone than is present in either the C. rubriventris or C.

floridana series.

In the above, as well as most other characters, the skull of C.

platymarginata differs little from that of its presumed descendant, C.

scripta. Certain differences, presumably adaptive, do exist, however.

Most obvious are the much broader maxillary surfaces of C. platymarginata

(Fig. 22B); this is principally due to expansion of the posterior part .,

91

of the alveolar surface medial to the longitudinal maxillary ridge.
Alveolar expansion is present in all Ha i 1 e XVA maxillae but seems most
highly developed in the largest individuals. The alveolar surface
incorporates a lateral projection of the palatine bone as it does in
extant members of the scripta, floridana and rubriventris groups. The.
supraoccipital of C. platymarginata appears slightly larger than in Recent
C. scripta, though C. platymavginata cranial material is insufficient to
test this statistically. This feature, coupled with greater lateral
expansion of the parietal roof in C. platymarginata, would provide
additional surface area for attachment of the adductor mandibulae
externus musculature (Gaffney, 1972).

Most of these morphological features indicate adaptation to coarser
or harder foods than those eaten by the omnivourous C. scripta. In
particular, they suggest a turtle with feeding habits similar to modern
C. nelsoni (unpublished data show post-hatchl ing C. nelsoni to be entirely
herbivorous). The broad pterygoids indicate that animal food may still
make up a significant part of the diet, however.

With knowledge of the skull of Chrysemys platymarginata, its
relationships to other species in the genus can now be studied. Other
than Rogers' (1976) report of C. scripta from Texas, the only Blancan
turtle known which may be a member of the C. scripta group is Chrysemys
idahoensis. Described by Gilmore (1933) from the Hagerman lake beds
(Upper Pliocene) of Idaho, the species is based not only on an entire
(though partially crushed) shell, but also on a remarkably preserved
and excellently illustrated skull (USNM 12059). Although unsure of its
generic identity (whether Pseudemys, Trachemys, or Graptemys) , Gilmore

92

believed the skull, with its broad alveolar surfaces, bore closest
resemblance to C. vuhriventris. He pointed out, however, that the skull
differs from C. vuhvlventvis by its broader pterygoids and less pronounced
median alveolar ridge with finer dent iculat ions . These features are
diagnostic of the Tvaoherrys group. Hay's (I908) improper description
of the lower jaw of that group led Gilmore to say that C. idahoensis could
not belong to Traohemys. Rose and Weaver (I967) noted the strongly
notched peripheral bones of C. idahoensis, but nonetheless concurred with
Gilmore's opinion of its affinities with the C. vuhriventris series.
Zug (1969) correctly points out that the cranial characteristics and
geographic distribution of C. idahoensis are actually more similar to
C. saripta than to the C. rubriventris line. The primary feature by
which previous authors associated C. idahoensis with the C. vuhviventvis
lineage is the broad alveolar surfaces of their jaws. Broad alveolar
surfaces have occurred in the C. scviyta lineage in the past, however,
as noted above in C. platymarginata . This characteristic is an adaptive
trophic feature which should not be employed per se to distinguish the
two groups. Additionally, in all Recent species assigned to the C.
ruhviventvis group (c. rubriventris, C. nelsoni, and C. alabamensis) ,
the vomer forms an integral part of the alveolar surface; the vomer of
C. idahoensis, like that of C. scripta, is recessed. All other features
used earlier to assign C. platymarginata to the Traohemys group are also
present in C. idahoensis. Gilmore (1933) points out the occurrence of
carapacial rugosity in the paratype of C. idahoensis and the wide pterygoids
of the type skull, both characteristic of C. scripta. The posterior
tapering of the shell and elevated (tent-like) pygal bone of the holotype,

93

considered as a species characteristic by Gilmore (1933) are probably
artifacts of post-mortem compression; both features are more nearly
"normal" in the paratype.

Although Zug (1959) contends that the broad alveolar surfaces,
coupled with robust inferior parietal processes, indicate mol 1 usci vory ,
I disagree. For reasons stated earlier i believe that these characteristics
in the genus Chrysemys are adaptations for herbivory.

The type skull figured by Gilmore (1933) appears at first glance
extraordinarily large for Chrysemys and particularly for Trachemys.
Comparison with Recent C. nelsoni and extrapolations for Recent C.
soripta of equivalent size (C. saripta does not reach this size today)
reveals that the skull of C. idahoensls is not significantly longer than
that of C. scripta or C. nelsoni though it is proportionately wider.
The skull of C. idahoensis rises abruptly posterior to the f ronto-par ietal
suture, effectively creating a higher and deeper supraocc i pi tal crest.
Whether this is an artifact of illustration or preservation, an aberrancy,
or a real adaptation allowing for attachment of hypertrophied jaw
musculature, remains to be determined upon collection of additional
cranial material .

I conclude that C. idahoensis is a valid member of the C. scripta
group; it is known from the Upper Pliocene of south-central Idaho, by
Gilmore's (1933) original material and by six additional elements
described by Zug (1969).

Two extinct species, C. idahoensis and C. platymarginata , both
clearly represent the Trachemys group. Both occur in Upper Pliocene
(Blancan) deposits, but their type localities are 33^5 km apart. The

9^

question arises as to whether these two turtles represent contemporaneous
but distinct lineages within the C. saripta group, or whether they might
actually represent two populations of a single widespread species. Were
it to be based only on records from Idaho and Florida, the latter
hypothesis could be seriously questioned on geographic grounds alone.
However, Zug (1969) identified the anterior half of a plastron (UMMP
\J-k2603) from the late Hemphill ian Wolf Canyon area of Meade County,
Kansas as C. iddhoensis. Additionally, among material collected by
J. A. Holman at Devil's Nest Airstrip, Knox County, Nebraska, are an
eleventh left peripheral bone (MSU VPS^Z) and a small xiph i plastron
(MSU VP832) which represent Traahemys and are indistinguishable from
C. idahoensis. The material from this site is tentatively believed to
be Hemphillian (J. A. Holman, pers. comm.). Finally, a series of
approximately 30 elements (MUVP 9267), including four nuchal bones,
from the Upper Pliocene (Blancan) Beck Ranch local fauna in Scurry
County, Texas, were assigned by Rogers (1976) to C. saripta. These fossils
are here reassigned to C. iddhoensis on morphological (e.g., peripheral
bone rugosity and flare) and temporal grounds. The Kansas and Nebraska
localities fall approximately midway between the type localities of C.
idahoensis and C. platymarginata , roughly 1^00 km from the former. its
additional occurrence in Texas suggests C. idahoensis must have occupied
much of midcont i nental North America during the Pliocene.

Today only a single polytypic species of Traahemys, Chrysemys saripta,
occurs along the Atlantic Coast from Virginia to northern Florida, westward
to southern Texas, and northward to northern Kansas, Missouri, and
Illinois (Conant, 1975). Thus, it is not unusual for species of this

95

group to be distributed over extensive areas and wide latitudinal ranges.
From a geographic standpoint, therefore, it would not be surprising if
C. platymavginata and C. idahoensis represent a single widespread late
PI iocene species.

Morphologically C. idahoensis and C. platymarginata are similar.
Both are large turtles (max CL greater than 300 mm) with a faintly rugose
carapace, notched peripheral bones, incised nuchal scute, and extensive
plastral scute overlap. The skulls of both are like C. saripta but with
a more extensive parietal roof, larger supraocc ipi ta 1 , and broader
alveolar surfaces. The distinct double-notching of the posterior
peripheral bones characteristic of C. savipta is evident in C. platymarginata;
although less pronounced, the condition does occur in some peripheral
bones of C. idahoensis (Zug, 1969; Rogers, 1976). Likewise, the mid-
dorsal keel and carapacial sculpturing are more pronounced in C.
platymarginata than C. idahoensis. However, these differences are no
greater than those existing between the Recent subspecies of C.
scripta—C. s. elegans and C. s. scripta. Where such minor differences
do occur, C. idahoensis more closely resembles the northern and western
C. s. elegans, and C. platymarginata the southeastern C. s. scripta.
Should C. idahoensis and C. platymarginata actually represent a single
species, the evolution of what we recognize as subspecific differences
may have begun by at least the late Pliocene.

I suggest that Chrysemys idahoensis (Gilmore) and Chrysemys
platymarginata Weaver and Robertson represent a single widespread species
of the C. soripta group. This is supported by their morphological
similarity, approximate contemporaneity, and existence of geographically

96

intermediate populations. Chrysemys platymarginata should therefore be
placed in the synonymy of C. iddhoensis. Based on present subspecies
distributions and minor morphologic differences in the Pliocene, it is
likely that populations from Idaho and the Great Plains were subspec i f ical ly
distinct from those in Florida.

Based on minor cranial and carapacial differences, Chrysemys
idahoensis is considered distinct from C. scripta (see Weaver and
Robertson, 1967, for carapacial differences). The carapace of C.
idahoensis is generally less rugose and more posteriorly flared, and the
upper triturating surface and parietal roof are more extensive than
those of C. scripta. These and other minor differences may be chronoclinal,
and the point in time at which we separate the species must necessarily be
in part an arbitrary decision. An examination of Tvaahemys fossils from
five Irvingtonian deposits (Coleman ilA, Haile XVI, Inglis lA, Pool
Branch II, and Punta Gorda) and six Blancan deposits (Haile lA and
XVA, Port Charlotte, and Santa Fe River I, IB, and VIM) in peninsular
Florida, and one early Irvingtonian site (Burnette Ranch, Seymour
Formation, Knox County) in Texas, reveals almost exclusively C. scripta
phenotypes in the Irvingtonian and predominantly C. idahoensis phenotypes
in the Blancan; some phenotypic mixture as well as i ntegradat ion occurs
in both. The shift from C. idahoensis to C. scripta is therefore believed
to have occurred from late Blancan to very early Irvingtonian.

Pal eoecology

Chrysemys idahoensis was a large, mostly herbivorous, polytypic
species that represented the C. scripta group over much of North America

97

during the Upper Pliocene. Its great latitudinal range may suggest a
more homogeneous climate in North America at this time, although C.
saripta today is adapted to a wide variety of climatic regimes. The
presence in the Hagerman fauna of mammals with extant southern
distributions likewise indicates that winters must have been milder
than at present (Zakrzewski, I969). Fossils of otters (Bjork, 1970),
beavers and voles (Zakrzewski, I969), large numbers of fish (Miller
and Smith, I967), frogs, water snakes (Holman, I968), water and shore
birds (Brodkorb, 1958; Feduccia, 1967; Murray, 1967), as well as the
pollen record (Leopold in Weber, I965), suggest a slightly wetter climate
and greater abundance of fresh water in the Hagerman area during deposition
than at present (Zakrzewski, I969). Chantel 1 (1970) concludes from the
frog fauna that Hagerman was probably a warm, wel 1 -vegetated floodplain
habitat. In light of this evidence, the occurrence of a C. saripta-] ike
turtle in Idaho is not surprising.

Pleistocene glaciation must have exterminated the northernmost
populations of C. idahoensis. Failure of the species (or of its presumed
descendant C. saripta) to reestablish northern populations may have been
due 1;o establishment of lower (harsher winter) temperatures coupled with
development of more xeric condition?. Drainage changes that must have
occurred (Miller, 1965; Taylor, I966) would have had profound effects on
the distributions of all aquatic vertebrate populations. Reestabl ishment
may have been further hindered by the successful invasion of another
aquatic emydid turtle, C. piata, although C. piata and C. saripta coexist
extensively today.

Populations of C. saripta in the Florida peninsula (as far south
as Palm Beach County) also disappeared later in the Pleistocene. Here,

competition with several, more efficient large herbivorous congeners (C.
floridana, C. nelsoni, C. conoinna) may have been the determining factor.
Alveolar surface width reduction and related changes between C.
idahoensis and C. scripta may indicate a shift from more specialized
herbivory to generalized omnivory in response to the immigration or
evolution of superior competitors. The shift towards increased carnivory
may have necessitated the reduction in body size which has occurred in the
C. sar-ipta line during late Pleistocene and Recent times. Should this be
the evolutionary strategy that led to modern C. saripta, the species'
abundance over most of its large range today attests to its marked success.

Systematic Conclusions

McDowell's (1964) characters defining the subgenus Trachemys are,
as pointed out by Weaver and Rose (I967), either invalid or insufficient,
although some (dentary shape, anterior triturating cusp and maxillary-
quadratojugal junction) are helpful when used in conjunction with other
characters. However, rather than redefine McDowell's subgenera, Weaver
and Rose (1967) state that his subgeneric groupings are totally invalid.
They contend that North American C. saripta (including fossil forms) are
actually more closely related to the C. rubriventris series than either
is to the C. floridana series. I cannot agree with their interpretation
for several reasons.

Firstly, they accepted the opinion of most previous authors (Hay,
1908) that the Eocene emydid fossil turtles from the Bridger and Uinta
Formations, assigned to the genus Echmatemys, were ancestral to most
North American emydid genera, including Chrysemys. Characters of the

99

skull and shell of Eohnatemys were accordingly considered to represent
ancestral conditions where they occurred in Chrysemys spp. Unfortunately,
their basic premise is probably incorrect. Many of the shells, and also
the only known skull, of Eahmatemys appear to represent the Neotropical
emydid genus Rhinoalemys (= Callopsis of Smith et al., 1976), considered
by McDowell (196A) to be the only New World genus in the subfamily
Batagurinae. Characters of "Eahmatemys" are thus of little value in
determining relationships within the genus Chrysemys.

The second problem with the interpretation of Weaver and Rose (1967),
as well as of McDowel 1 (196't) in some instances, is the failure to
recognize morphological convergence due to ecological adaptation. Such
characters as shell shape, alveolar surface width, and scute overlap and
underlap reflect specific adaptations to the environment and not necessarily
phylogenetic relationships. In aquatic turtles, for example, narrow
scute overlap and underlap, by decreasing turbulence of a submerged turtle,
are adaptations to lotic environments (as witness their occurrence in
such distantly related riverine turtles as Gvaptemys, Podoonemis, Chrysemys
ooncinna, Trionyx, etc.). The fact that C. saripta and C. nelsoni have
greater scute overlaps does not imply a close phylogenetic relationship
but rather reflects evolutionary responses to similar ecologies (occupation
of more lentic habitats). Alveolar surface width has already been shown
to vary between closely related forms (C. saripta and C. idahoensis) and
must therefore be treated very cautiously as a phylogenetic character.
Such characters as strong peripheral bone notching have surely arisen
independently in C. saripta and C. concinna and can therefore not be
regarded as primitive to the entire genus.

100

Finally, as I have shown previously (Chapter III), fossil evidence
does not indicate a close relationship of C. saripta to the C. rubriventris
series as stated by Rose and Weaver (196?) and Weaver and Rose (196?).
Furthermore, structure of the choanae imply a distinct dichotomy between
the C. saripta series and all members of the C. flor-idana and C.
rubriventris series (Parsons, I960).

For these reasons the phylogeny proposed by Weaver and Rose (1967)
should be rejected. McDowell's (1964) concept of the genus seems more
realistic. Whether his subgenera would be better considered distinct
genera must await study of the fossil record of C. piota.

With knowledge of the Upper Pliocene Traohemys described in this
paper and that of Gilmore (1933), I present the first diagnosis of the
group that incorporates characters of both the shell and skull as they
have evolved through time. This diagnosis does not attempt to include
Mexican, Antillean, and Central and South American forms as their relation
to the C. scripta complex remains unclear (Weaver and Rose, 1967).

Characters clearly associated with all known North American
Traohemys are pterygoids broad and extending posteriorly to exocci pi tal s;
alveolar maxillary ridge without cusps or strong serrations; vomer not
participating in alveolar surface; mandibular symphysial ridge absent
or inconspicuous; anterior and posterior peripheral bones notched (some
doubly); nuchal scute sulci incised deeply on nuchal bone; medial
longitudinal keel present at least posteriorly; carapace but not plastron
usually with some longitudinal wrinkles; gular and femoral scutes broadly
overlapping plastron; and nuchal scute underlap longer than wide. The
number of phalanges is unknown in fossil forms.

101

Further Problems

Ciwysemys idahoensis is clearly not the progenitor of the Trachemys
line; it appears too late in the fossil record and already shows most of
the diagnostic characteristics, such as the doubly toothed peripherals,
of modern C. soripta. Chrysemys hillii (Cope), as expanded by Adler
(1968) to include C. lirrmadytes (Gal breath, 19^8), is known from the
early Pliocene of Oklahoma and Kansas. Adler (I968) points out a number
of similarities of C. hillii to C. soripta, including slight notching of
the posterior peripheral bones; he speculates that the fossil species
may be ancestral or closely related to C. soripta. Cope (I878) himself
suggested such a relationship and was followed by Hay (1902, I9O8), who
referred the species to Trachemys. I have not yet seen the types of
either C. hillii or C. limondytes; however, from Hay's (I908) excellent
photograph and Galbreath's (1948) illustration, I am inclined to agree
withAdler's (I968) hypothesis.

The presumably middle Pliocene Chrysemys inflata (Weaver and
Robertson, 1967), still known only from peninsular Florida, remains
ambiguous. Until further material is discovered I will fol low Weaver
and Robertson's (I967) suggestion that "it was a specialized or aberrant
species characterized by an extreme development of Traohemys features
and not representative of the main evolutionary sequence leading to recent
C. soripta." (p. -65) I additionally hypothesize that C. inflata represents
a pre-Blancan isolate from C. idahoensis stock that, by genetic drift or
perhaps in response to unique environmental stresses, developed its
massive, gothic shell. its failure to persist, as well as its subsequent
replacement in the peninsula during the Pleistocene by more conventional

102

C. saripta stock, may indicate overspec ial izat ion or ma ladapt i veness to
a changing environment. It is not surprising that C. inflata is known
only from peninsular Florida, where C. idahoensis (platymarginata)
appears to have developed the largest and most massive shell within its
range. I predict that C. inflata will not be found elsewhere.

The recent discovery of James L. Dobie (pers. comm.) of the nearly
complete carapace of a Chrysemys saripta (TMM 31081-280) from Bee County,
Texas, in the collections of the Texas Memorial Museum, is confusing.
The shell is reportedly from the Goliad Formation (late Miocene-early
Pliocene). It is, however, remarkably similar to Middle and Upper
Pleistocene C. saripta, particularly W\IPhS^(> (Texas I rv i ngton ian) .
I suspect that, through a data mix-up or deposltional quirk, the shell
may be Pleistocene. The alternative is that C. saripta existed as early
as Middle Pliocene (perhaps including C. hillii) , and that turtles
assigned to C. inflata and C. idahoensis represent a now extinct second
line of Traohemys in North America.

Finally, the status and relationships of the several Mexican,
Central and South American, and Antillian extant forms assigned to the
C. saripta complex (Williams, 1956; McDowell, 1964; Weaver and Rose,
1967; Moll and Legler, 1971) remain to be determined. As shown
previously many of the relationships suggested by Weaver and Rose
(1967) are based on inadequate characters; hence, their conclusions
regarding the relationships of the Neotropical turtles in this complex
must be reexamined. Unfortunately, these turtles are essentially
unknown as fossils. I suggest that they be retained provisionally as
members of the C. saripta complex as put forth by Williams (1956).

Figure 22A. Posterior palatal surface of_si<ull (UF 21963) of
Chrysemys idahoensis from Halle XV.

Figure 22B. Alveolar surface of right maxilla (UF 23921) of
C. idahoensis from Ha i 1 e XV.

\0h

CHAPTER V
PRE-PLIOCENE RECORDS OF THE GENUS CHRYSEMYS

Emydid turtle fossils have been reported from only two of the
several Miocene deposits known from Florida (Olsen. 1 964b) --Thomas Farm
in Gilchrist County (Williams, 1953) and the Seaboard Air Line Railroad
Company in Leon County (Olsen, 1964a). The fossils fron both sites were
referred to the genus Chrysernys (sensu McDowell, 1964) and, in conjunction
with its presence in an 01 igocene deposit (Patton, I969), mark the
earliest known occurrence of the genus. In light of its wide distribution
and significant role in the North American turtle fauna, these early
records of the genus Chvysemys are of considerable importance. After
examining fossils from these sites I find that a reappraisal of the
material is necessary.

Materials and Methods

I examined all previously described Thomas Farm fossils from the
Museum of Comparative Zoology (MCZ) as well as additional undescribed
material from the Florida State Museum (UF) . The Seaboard fossils,
formerly housed by the Florida Geological Survey, are now also in the
Florida State Museum, as are the 1-75 fossils. Comparative skeletal
material was examined from the Florida State Museum (UF) herpetology
collection as well as the author's (DRJ) personal collection (the latter
to be incorporated into the UF collection).

105

106

Site Records for Chrysemys

1-75

Patton (1969) lists the occurrence of "Pseudemys sp." in this site,
the only known nonmarine 01 igocene deposit in Florida. Unfortunately,
some of the vertebrate fossils from this site have been lost (T. Patton,
pers. comm.). Of the chelonian fossils available (UF I6897- I6899) , the
only identifiable fragments represent land tortoises.

Seaboard Air Line Railroad Company, Switchyard B

Olsen (I96'*a) recognizes "pieces of the plastron and carapace of
the terrapin Pseudemys sp. idet." from this Lower Miocene deposit in the
Florida panhandle. Having examined all of the turtle material from this
site, I find no fossils that can be assigned to any emydid genus. Several
fragments labeled "Pseudemys hypoplast ron" proved, upon reconstruction, to
be a large posterior peripheral bone of a sea turtle (UF 21952). The only
other fossils labeled Pseudemys are actually fragments of a xiph iplast ron
(UF 21953) and pleural bone (UF 21954) from two small tortoises
(Testudinidae) . As Olsen (1964) reports the presence of the tortoise
Geoohelone and four genera of marine fishes, neither reassignment contradicts
his conclusions about the stratigraphy and paleoecology of the site.

Having eliminated the 01 igocene and one of the two Miocene reports
of Chrysemys , we must now examine the remaining Miocene record more
closely.

Thomas Farm

Williams (1953) first noted the presence of emydid turtle fossils
in the Thomas Farm Lower Miocene fauna and tentatively assigned them to

107

the Chrysemys floridana group. Rose and Weaver (I966) affirmed the generi
designation but reassigned the fossils to the C. rubriventris group.
However, none of these workers realized the antiquity of the fossil record
of the genus Beirochelys (Chapter II), nor did they have any reason to
suspect its occurrence in the Thomas Farm fauna. Confirmation of the
presence of Deivochelys in this fauna (Chapter II) therefore necessitates
a reexamination of all emydid material from this site.

The inclusion of Chrysemys as a member of the Thomas Farm fauna,
based only upon the original material (MCZ 3^32), would be questionable
were it not for two adjacent neural bones (UF 21933) collected since
Williams' paper. The two neural bones (Fig. 23), though possessing an
anomalous common sutural border dorsal ly, are clearly the second and
third neural bones of a relatively small Chrysemys (estimated carapace
length 220). They are longer than wide (length:width ratios of 1.2 and
1.1, respectively), unlike Deiroohelys (Chapter II), and possess no
middorsal keel. Their dorsal surfaces are finely rugose, and the neural
spines are low and robust. A posterior neural bone (UF 21935) almost
certainly representing Chrysemys further indicates the absence of a
strong keel. The lack of a keel or of any gross surface sculpturing is
characteristic of McDowell's (I96i») subgenus Pseudemys and the C. omata
group of the subgenus Traahemys.

With the occurrence of Chj'ysemys in the Thomas Farm Miocene thus
reaffirmed, we may suspect that most of the emydid fossils probably do
represent this genus. However, until complete material represents both
genera in the Miocene, it will be difficult to assign many of the
individual Thomas Farm bones to either genus with certainty. Neverthe-
less, as all of the unworm peripheral and pleural bones from the site

exhibit a finely to moderately rugose surface, we may conclude with some
assurance that the Thomas Farm Clwysemys possessed a rugose carapace
similar to that of C. nelsoni and the Pliocene C. oaelata (Chapter III).

Because of the importance placed on the nuchal bone by most
chelonian paleontologists, I am obligated to comment on the Thomas Farm
nuchal s. Without knowledge of the presence of Deirochelys in Thomas
Farm, both Williams (1953) and Rose and Weaver (I966) naturally assumed
them to represent Chrysemys. Rose and Weaver pointed to the resemblance
of the nuchal scute underlap of the complete nuchal bone (see their Fig.
2B) to that of C. nelsoni and the Pliocene C. oaelata (their C. oai>ri;
see Chapter II). The similarity also holds for the two fragmentary nuchals,
but, more importantly, equivalent nuchal scute underlaps for all three
may be found in Deirochelys as well (e.g., UF Ukk; DRJ 300, 305).
Furthermore, Rose and Weaver (I966) overlooked the importance of the
laterally expanded first vertebral scute (see Williams, I953, Plate 4b) ,
evident on both nuchal bones in which the sulci can be seen. Only in
Deirochelys and the Pliocene C. wilUamsi among Florida emydids is the
first vertebral scute regularly this wide. This condition occurs as an
uncommon variant in both C. nelsoni (e.g., DRJ 225) and C. floridana
(e.g., DRJ 255). However, the nuchal scute underlap is much longer than
that of C. WilUamsi. In conclusion, the nuchal bones represent either
Deirochelys or an undescribed species of Chrysemys that combines features
of two Pliocene species, C. oaelata and C. wilUamsi. Interestingly,
this combination of characters is common today in the Central American
turtle, C. ornata.

109

Discuss ion

Williams (1953) tentatively assigned the Thomas Farm Chvysemys to the
floridana group on the basis of shell rugosity and other unspecified
details. Rose and Weaver (I966) rightly pointed out that the pleural
bone rugosity bore stronger resemblance to that of C. nelsoni and C.
caelata and, based on this and two other characters that must be questioned
on the grounds that they may have been drawn from Deirohelys, referred the
Thomas Farm fossils to the nelsoni-whviventvis complex.

It is not yet clear which of these two viewpoints is correct.
Indeed, there is no evidence to indicate that these two lines within the
subgenus Pseudemys (i.e., nelsoni-vuhviventvis and flovidnna-concinna)
had diverged by the Miocene. (For reasons given in Chapter IV, I cannot
agree with Rose and Weaver's [I966] hypothesis of a close relationship
between C. nelsoni and C. soripta.) in fact, an Oligocene or early
Miocene turtle like that at Thomas Farm, with strong resemblance to C.
ovnata, would seem sufficiently generalized to give rise not only to both
lines of Pseudemys {rubviventris and floridana) but to Trachemys as well.
A final pal eoecolog lea 1 note may be added. Among freshwater emydid
turtles, a rugose carapace and relatively long nuchal scute underlap seem
to be associated with occupation of quiet waters, and a smooth carapace
and short nuchal scute underlap with more strongly flowing water (these
are only two of what appears to be a complex of habitat-related
morphological characters). Regardless of generic affiliations, the nuchal
scute underlap and carapacial rugosity of the Thomas Farm emydid fossils
therefore imply that the Lower Miocene environment of Thomas Farm included
slow-moving or still water, as previously suggested by Auffenberg (I963).

Figure 23. Dorsal and visceral surfaces of second and third
neural bones (UF 21933) of Chrysemys from Thomas
Farm (x 2.2).

Ill

APPENDIX
FOSSIL LOCALITIES CONTAINING DEIEOCHELYS

Miocene: Arikareean site
Thomas Farm, Gilchrist County.

Auffenberg (1963a) reviews the geology and literature pertinent to
this site in addition to discussing its ophidian fauna. He interprets
the site as representing a lower Miocene fissure fill and points out
biotic evidence for the presence of slow-moving or still water during
that time.

Pliocene: Hemphillian sites
Haile Vl, Alachua County.

One of a series of Pliocene sites assigned to the "Alachua Formation"
of Florida, parts of its pa leoherpetofauna have been treated by Auffenberg
(1955, 1963a), Coin and Auffenberg (1955), and D. Jackson (Chapter III).
Auffenberg (1963a) discusses the stratigraphy of the deposit and states
that it represents an ancient stream bed. The site lies approximately
26 m above present sea level.

Love Bone Bed, Alachua County.

This previously unreported site (29°33'N, 82°31'W; Sec. 9, TllS
R18E) near Archer, Alachua County, Florida, is named for Ronald Love who
discovered it in 1974; it is now being excavated by the Florida State
Museum under the supervision of S. David Webb. Preliminary strat igraphic
studies reveal that the deposit represents the "Alachua clays" which were

112

113

laid down in an ancient stream bed cut into uplifted Eocene Ocaia
1 imestone.

The presence of the horses Hipparion pUaatile Leidy and Nannippus
ingenuus (Leidy). an early Osteoborus dog, the artiodactyls Synthetooeras
and an advanced Cranio cer as , and an early saber-cat of the genus
Bopbourofelis (S. D. Webb, pers. comm.), as well as the turtle Chrysemys
caelata Hay (Chapter III), indicates an early Hemphill ian fauna roughly
equivalent to that of McGehee Farm and Mixson's Bone Bed.

McGehee Farm, Alachua County.

An early Hemphill ian site in the Alachua Formation (Rose and Weaver,
1966; Hirschfeld and Webb, I968), McGehee Farm is the type locality of the
Pliocene emydine turtle Chrysemys wilUamsi (Rose and Weaver, I966), the
tortoise Geoahelone alleni (Auffenberg, I966), and the chelydrid
Maaroalemys auffenbergi (Dobie, I968), and has additionally yielded
abundant material representing Chrysemys oaelata (Chapter III) and
Trionyx sp.

Mixson's Bone Bed, Levy County.

The first known Pliocene deposit (Dall and Harris, 1892,- Leidy and
Lucas, 1896) within the type section of the Alachua Formation (Simpson,
1929a) of Florida, Mixson's Bone Bed is the type locality of Hay's (I908)
Chrysemys oaelata (Chapter III).

Pliocene; BJancan site
Haile XVA, Alachua County.

This deposit represents a former sinkhole filled with alternating
coarse sands and clays. The fauna, assigned to the Aftonian interglac ial,

11^

is characterized by a rich assortment of aquatic and terrestrial vertebrates,
including the turtle Chvysemys platymarginata (Weaver and Robertson, I967)
for which the site is the type locality. Although now Ik m above present
sea level the presence of marine vertebrates in the fauna indicates higher
sea level during deposition and a decided estuarine influence (Kinsey,
197^; S. Webb, 197^). Robertson (1976) presents a detailed account of
the stratigraphy and the mammalian fauna of the deposit.

Pleistocene: Irvingtonian site
Haile XVI, Alachua County.

An undescribed pit (29°^0'40"N, 82°3^'20"W; Sec. 25, T9S, R17E) in
the Haile limestone quarries (Ligon, I965) excavated by the Florida State
Museum under the supervision of S. David Webb in May, 1973. The fauna
appears to be i nterg lacial , of Irvingtonian age, and may represent the
first known Yarmouthian deposit in Florida. A more detailed discussion
of the deposit will accompany reports of faunal studies presently being
conducted .

Pleistocene: Rancholabrean sites
Bradenton 51st Street, Manatee County.

A coastal marsh 3 m above present sea level (S. Webb, 197^), the
site is discussed by Simpson (1930a, b) and Auffenberg (1958; 1963a) and
is now known to represent the Sangamonian interglacial (S. Webb, 197^).

Coleman IMC, Sumter County.

An undescribed deposit (Sec. 7, T20S, R23E) of Rancholabrean age
(S. D. Webb, pers. comm. ) , this site, like previously reported Coleman

115

deposits (Martin

197^), represents a filled sinkhole in the late Eocene

Ocala Limestone;

its surface lies approximately 24 m above present sea

level .

Kendrick lA, Marion County.

A sinkhole-fissure fill near Kendrick, the deposit lies approximately
2k m above present sea level. Kurten (I965) and Brodkorb (I959) assign

the fauna to the illinoian or early Sangamonian although Auffenberg (I958)

and S. Webb (197^) believe it to represent the Wisconsinan.

Reddick IIC, Marion County.

Approximately 2k m above present sea level, this inland deposit
represents a Pleistocene sinkhole or fissure fill containing a Rancho-
labrean fauna (S. D. Webb, 197^).

St. Petersburg, Catalina Gardens, Pinellas County.

A small, previously-unreported deposit (Sec. 12, T32S, R16E) at
approximately present sea level, its fauna is apparently Rancholabrean
in age (S. D. Webb, pers. comm.).

Seminole Field, Pinellas County.

A Pleistocene coasta] marsh three meters above present sea level,
Simpson (1929a), Auffenberg (1958) and Kurten (I965) assign this site
to the Wisconsinan glacial period. Cooke (1926) and Simpson (1929a)
give accounts of the stratigraphy of the deposit. Simpson (1929a, b,
1930b) lists the mammalian fauna, and Gilmore (1938), Brattstrom (1953)
and Auffenberg (1963a) the snake fauna.

116

Vero, Indian River County.

Only three meters above present sea level, this site is considered
by most recent authors (Weigel, 1962; Auffenberg, 1963a; Webb. 197^) to
represent the late Wiscons inan glacial period. Weigel (I962) discusses
Its stratigraphy and vertebrate fauna (but does not include Deirochelys)
and reviews the extensive literature pertaining to the site.

Waccasassa River I. V. and VI. Levy County.

Although S. Webb (1974) includes site VI in his chronology of
Florida Pleistocene localities, neither of the other deposits which
have yielded Deirochelys (l, Sec. 20 and V. Sec. 32. TI3S. R16E) has
been mentioned. The sites are 6 m to 7 m above present sea level and
contain Rancholabrean faunas (S. D. Webb, pers. comm.).

Wall Company Pit, Alachua County.

The stratigraphy of this small fissure deposit is briefly discussed
by Auffenberg (1963a). Auffenberg (1958) tentatively assigns the deposit
to a time between the illinoian glacial maximum and the Sangamonian
interglacial maximum.

Subrecent sites
Nichol's Hammock. Dade County.

Hirschfeld (I968) describes the geology, pal eoecology, and
vertebrate fauna of this solution hole site. Her herpteofaunal list
includes Deirochelys retioularia.

Warm Mineral Springs, Sarasota County.

Ferguson et al. (19^7) describe the hydrology and topography of
this spring (Sec. 25, T39S. R20E. less than six meters above present sea

17

level) under the name of Warm Salt Spring. Clausen et al. (1975)
present a detailed description of the geology of the deposit for which
they report a radiocarbon age of approximately 10,000 years. Fossils
are currently being excavated by the Florida Department of State under
the direction of W. A. Cockrel 1 .

LITERATURE CITED

Adler, K. I968. Synonymy of the Pliocene turtles Pseudemys hilli Cope
and Chrysemys limnodytes Galbreath. J. Herpetol . 1: 32-38.

Agassiz, L. 1857. Contributions to the natural history of the United
States of America. Vol. 1, 2. Little, Brown and Co., Boston.
640 p.

Alt, D. 1957. Pattern of post-Miocene eustatic fluctuation of sea level
Geol. Soc. America, Southeast Sec. Program, p. I5.

_, and H. K. Brooks. 196^. Age of the Florida marine terraces.

J. Geol. 73: 406-4ll.

Auffenberg, W. 1955. Glass lizards {Ophisaurus) in the Pleistocene and
Pliocene of Florida. Herpetolog ica 11: I33-I36.

• 1958. Fossil turtles of the genus Terrapene in Florida. Bull

Florida State Mus. 3: 53-92.

• 1963a. The fossil snakes of Florida. Tulane Stud. Zool

10: I3I-2I6.

• 1963b. Fossil testudinine turtles of Florida. Genera

Geochelone and Flovidemys . Bull. Florida State Mus. 7: 53-97.

• '966. A new species of Pliocene tortoise, genus Geochelone,

from Florida. J. Paleontol. 40: 877-882.

197^. Checklist of fossil land tortoises (Testud in idae)

Bull. Florida State Mus. 18: 121-251.

Baur, G. I889. The relationship of the genus Deiroohelys. Amer. Nat
23: 1099-1100.

Beyer, G. E. I9OO. Louisiana herpetology. Proc. Louisiana Soc. Nat.
1897-1899: 25-46.

Bickham, J. W. 1975- A cytosystemat i c study of turtles in the genera
Clemmys, Mauremys and Sacalia. Herpetologica 31: 198-204.

, and R. J. Baker. 1976. Chromosome homology and evolution of

emydid turtles. Chromosoma (Berl.) 54: 201-219.

Bjork, P. R. 1970. The Carnivora of the Hagerman local fauna (Late
Pliocene) of southwestern Idaho. Trans. American Philosophical
Soc. 60: 1-54.

118

19

Boulenger. G. A I889. Catalogue of the chelonians, rhynchocephal ians
and crocodiles in the British Museum (Natural History). Brit sh
Mus. (Nat. Hist.), London. 311 p.

Bramble DM 1973. Media dependent feeding in turtles. Amer. Zool.

13: 13^2

I97J. Emydid shell kinesis: Biomechanics and evolution.

Copeia 197/*: 707-727

Brattstrom B. H 1953. Records of Pleistocene reptiles and amphibians
from Florida. Quart. J. Florida Acad. Sci. 16: 243-2^8.

Brodkorb. P. 1958. Fossil birds from Idaho. Wilson Bull. 70: lH-lkl.

1959. The Pleistocene avifauna of Arredondo, Florida. Bull.

Florida State Mus. k: 269-291.

Brooks H. K I966. Geological history of the Suwannee River. In N K
Olson (ed.) Geology of the Miocene and Pliocene series in the '
north Florida-south Georgia area. Atlantic Coastal Plain Geol
Assoc. 7th Ann. Field Conf. and Southeastern Geol. Soc 12th
Ann. Field Conf.

Cagle F. R. I952. The status of the turtles Gvaptemys pulchra Baur and
Gvaptemys barbour^ Carr and Marchand, with notes on their natu al
history. Copeia 1952: 223-23^.

.. 1953. Two new subspecies of Graptemys pseudogeographica.

Occas. Pap. Mus. Zool., Univ. Michigan, no. 5^6: I-I7.

Z^ol ^?^^i67-T86"^'' species of the genus Graptemys. Tulane Stud.

Campbell. H^W.^^,96_9^^^The unsung chicken turtle. int. Turtle. Tortoise

^^'''' m'v^' JP" "^"^'^°°'< °^ turtles. Comstock Publ . Assoc, Ithaca
N . r . i)42 p. '

., and L. J. Marchand. 19^2. A new turtle from the Chipola

River, Florida. Proc. New England Zool. Club 20: 95-100.
^^^"^^'h-eek'^' ^^^°' ^PP^-" f'"^""^ f'-ogs from Idaho. Copeia I97O:

Clausen C. J. H. K Brooks, and A. B. Wesolowsky. 1975- Florida spring
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BIOGRAPHICAL SKETCH

Dale Robert Jackson was born in Boston, Massachusetts, on December
17, 19^9. He entered Eastern Illinois University in September, I967,
and received the degree of Bachelor of Science with a major in zoology
in June, 1971. Setting out to seek his fortune, the naive midwestern
youth journeyed southward and, in September that same year, entered the
Graduate School of the University of Florida. There he pursued the
degree of Doctor of Philosophy in the field of zoology.

He is a member of the American Society of Ichthyologists and
Herpetologists, American Society of Naturalists, American Society of
Zoologists, American Association for the Advancement of Science, and
the National Audubon Society.

He is unmarried, has no children to his knowledge, and is now
seeking happiness rather than fortune.

128

I certify that I have read this study and that in my opinion it

conforms to acceptable standards of scholarly presentation and is fully

adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.

Walter Auffenber^^, Chi'j/man
Professor of iQjsAoqy '''^

I certify that I have read this study and that in my opinion it

conforms to acceptable standards of scholarly presentation and is fully

adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.

tan

^l/lA/^^

Carmine A. Lancianl

Associate Professor of Zoology

I certify that i have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.

Frank G. Nordl ie
Professor of Zoology

I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.

Assistant Professor of Geology

I certify that I have read this study and that in my opinion it

conforms to acceptable standards of scholarly presentation and is fully

adequate, in scope and quality, as a dissertation for the degree p^-
Doctor of Philosophy.

S. David'Welib " \^ V
Professor of Zoology

This dissertation was submitted to the Graduate Faculty of the Department
of Zoology in the College of Arts and Sciences and to the Graduate Council,
and was accepted as partial fulfillment of the requirements for the degree'
of Doctor of Philosophy.

August, 1977

Dean, Graduate School

UNIVERSITY OF FLORIDA

3 1262 08553 2884