BULLETIN
OF THE

FLORIDA STATE MUSEUM

BIOLOGICAL SCIENCES

Volume 10 Number 5

THE CARPUS OF LAND TORTOISES (TESTUDININAE)

Walter Auffenberg

UNIVERSITY OF FLORIDA
Gainesville

1966



Numbers of the BULLETIN OF THE FLORIDA STATE MUSEUM are pub-
lished at irregular intervals. Volumes contain about 800 pages and are not nec-
essarily completed in any one calendar year.

WALTER AuFFENBERG, Managing Editor

OLIVER L. AUSTIN, JR., Editor

Consultants for this issue:

E. C. Olsen

A. S. Romer

Communications concerning purchase or exchange of the publication and all
manuscripts should be addressed to the Managing Editor of the Bulletin, Florida
State Museum, Seagle Building, Gainesville, Florida. 32601

Published February 18, 1966 Price for this issue $.55



THE CARPUS OF LAND TORTOISES (TESTUDININAE)

by
' WALTER AUFFENBERG 1

SYNOPSIS: This study 6f the manus of <50 species of living and fosiil tortoises

shows their structure t9 be considerably more variable than formerly presumed.
The carpal pattern of' each of'the species studied is described and most are illus-
trated diagrammatically. Certaih babe structural pattetns reflect both the phy-
16tic rel#i*lships of  these species and the kitieties 6f.ihe foot and stresses placed
on it during locomotion.

The- carpal architecture of torjoihes is easily-deriyed from thalt of a.' general.
ized amphibian.ora primitive 'reptilian arrangement. Some species of toridises
pos6655 a distinct, Droximal 6€litrale, hete reported for the firSt time ih.aily reptile.
Qther dissinlilarities between the carnus ·6f·,the tortoises and thode of, other rep-
tiles are probably due to simple loss a.ful/Or fusion of plements, fusion being ap-
parBntly much more common·than loss in tortoises. The probable homologies
Of tortdise carpal elements  are disbussed. Tre1id5 in moiphological and_functional
evolution of the carpus are: (1) subradial and· subulnur .lateral migration of ele-
ments, '(2) fusion of PFoximal subradial and subulrlar elements,: and (8) fusion of '
distal carpal elements.

CONTENTS
Page

Introduction ·. .4. 160
Homologies and  Major Patterns .'161
Descriptions 167
Functiohal, Aspects 181
·Phylogenetic Aspects - 185
Literature ,€ited 189

1

i The author is  Ass6ciate Curator iii· Herpetplogy, Florida· State Museum.
Most of his re8earchfs have dealt with the evolutionary biology of amphibians
and. reptiles. Earlier canfributibns t«'the Bulletih coicern fosill'tuitles and ihe
musculattire of salaman'ders. , Manuscript submitted 7 Octobe¥ 1965.-ED: : -

Auffwb-erg, Walter. 1966: /The tirpus of Land.Tortoises (Testudinjnae). Bzill.  .
Eldrida· Stat€ Mus-., *61. 16,  ·no. 5, pp. 159-101.



INTRODUCTION

The aim of this paper is to describe the morphology and major
functional features of the carpus of land tortoises. It is part of a
continuing study of the evolution and systematics of fossil and Recent
tortoises of the world.2 A study 6f  the tarsus of land tortoises is pres-
ently under way.

A summary Of the functions and evolution of the amphibian and
reptilian tarsus has been published (Schaeffer, 1941), but no similar
study has been made of the carpus. S6me general accounts of the
carpus in reptiles are available (Hoffman, 1890; Homer, 1933.,aad 1956;
Sieglbaufer, 1909; Williston, 1925; et. al.), and numerous isolated pa-
pers describe the carpus of specific reptile and amphibian groups
(Baur,.1885,1888; Dollo, 1929; Cegenbauer, 1864; Gregory, Miner and
N6ble, 1928; Hartmann-Weinberg, 1929; Howell, 1985; Nauck; 1924;
Rabl, 1916; Ribbing, 1909; Romer, 1983„ 1956; Sieglbaurer, 1909;
Sj6gren, 1940; Steiner, 1920-1921; Wiedersheim, 1876; Williston, 1914;
et at.). .The carpus of the land tortoises has never.been, extensively
studied, and those of only a few species have .been described in de-
tail (Flower, 1924, 1983; Hewitt, 1937; Schmidt, 1919; et al.). Though
no comprehensive treatise is available on the devdlopment of the ;car-
pus of land tortoises, Hoffman (1890) dis¢usBes certain aspects of the'
carpal embryology of Geochelone -denticulata, Walker's papBr on
Chrusen*'3 (1947) is pertinent, and Shah and Patel (1964) have re-
cently described the myology of the front limb of a land tortoise.

The present study indicates that the carpus of tortoises exhibits
considerably more individual and ont6genetic variation than was _
generally presumed. Yet within this extreme range of individual di.
versity a series of basic structural. patterns is manifest, each charac-
terizing the major tortoise groups currently rec6gnized. The struc-
tural patterns refiect the relationships of these groups to one another,
as well as the kinetics of the foot and the stresses placed upon it dur-
ing locomotion.

The articulated front feet of 80 species,of land tortoises were ex-
amined. Individual and ontogenetic variations were studied in those
species,for which a number of skeletons was  available.. Diagrammatic
drawings of each of the feet examined provid6 a more uniform.basis
for coinparison of"the·considerable variation in th6 shape of the indi-
vidual elements: ·Articulaf. details and 'the.-presence or abse#ce of
pertain units are considered more -important than minor variations
:in shape.

2 Partially supported·,by NSF GB1362, GB2725, and the American Philosoph- .
ical Sddietk



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 161

Discussion of the functional aspects is necessarily superficial be-
cause of the lack of living material representing all the major carpus
patterns known in tortoises. The function of the carpus and its rela-
tion to the movements Of the fronf limb and body as a whole was
studied from slow motion photographs showing the locomotor pat-
terns of tortoises of several different genera. Analysis of these photo„
graphs, together with experiments on the kinetics of preserved feet
and skeletal material, provided data useful in interpreting the varia-
tion and pattern of carpal architecture.

This study could not have been completed without the assistance
of a great number of persons, to whom I owe my deepest apprecia-
tion. In particular I wish to thank the individual curators of the
collections listed below for permision to examine skeletal material
in their care:

AMNH-American Museum of Natural History (Charles M. Bo-
gert)

BMNH-British Museum of Natural History (Alice G. C. Grandi-
son)

BNHS-Bombay Natural History Society (J. C. Daniel)
CAS-California Academy of Sciences (A. Leviton)
CMNH-Chicago Museum of Natural History (Robert Inger)
MCZ-Museum of Comparative Zoology (Ernest E. Williams)
PPHM-Panhwidle-Plains Historic Museum (Jack Hughes)
SNHM-Stanford Natural History Museum (Geerge Myers)
UCM-University of Colorado Museum (Paul Maslin)
UK-University of Kansas (William Duellman)
UMMP-University of Michigan Museum of Paleontology (Claude

H. Hibbard)
UMMZ-University of Michigan Museum of Zoology (Charles

Walker)
USNM-United States National Museum (D. Cochran)
UT-University of Texas (Frank Blair)
UT-A-University of Tel-Aviv (H. Mendelsohnn)
VNHM-Vienna Natuthistorishe Museum (Josef Eiselt)
ZSI-Zoological Survey, India (M. N. Archarji)

HOMOLOGIES AND MAJOR PATTERNS

The distal ends of both the radius and ulna of land tortoises are
always expanded in the same plane, forming a firm, linear foundation
for the carpals, which are similarly aligned. The structural plan of



162 BULLETIN FLORIDA -STATE MUSEUM Vol. 10

the man-us is usually plantigrade or digitigrade;.the phalangeal ar-
rangement is always palmate. Being in a single plane, the carpus is
effective in ,transferring the weight of the front part of the animal·.to
the 'toes. Shrearing stresses are controlled by strong, sheet-like liga-
ments that bind the entire bony complex together.

The usual number of bones in: the carpometacarpus of extant tor-
toises is 12, though fusion and/or loss may reduce them in some spe-
cies to as few as 5: Regardless of numbe~'or homology, the elements
comprising the carpus in the tortoises tend to be distributed in three
rows. ' The. upper row is usually composed of three bones; one ar-
ticulates with the distal end of the radius, a more medial.and usually
smaller element articulates With both the radius and the ulna, and the
last -articulates with the distal end of the ulna. The two lateral ele-
ments may be fused to more distal members in some species. The
number of elements comprising the middle row varies from one to
three. Each is normally articulated with one or more elements in
the proximal series and with one or more distal carpals; or these mid-
dle elements may be fused with either of these series or with -adjacent
lateral elements. A median element lying between the proximal row ,
of central Wind the distal carpals is often all thaf remains of this series:
Five distal car#als·(true carpals) usually comprise the- lower row,
though fusion with one. another, or  with adjacent medials (centrals),
or with nietacarpals is common. The outer distal carpals may articu-
late with either the, radius 6r the ulna.

Metacarpals I-V are usually present,.but fusion - with adjacent
phalanges or with the distal carpals is common. There are never
more than two phalanges in each digit, though the proximal pha-
langes may be fused with the adjacent metacarpals. Most species
have 5 digits, a few only 4, and in some species the number character-
istically varies between 4 and 5. The pisiform when present usually
articulates with the ulna and one of the external carpals; when ab-
sent it is r6presented by a cartilaginous element of variable density
in the sheet of connective tissue that binds the carpals together.

The homologies of the elements comprising the turtle carpus have
not yet been established beyond question. In fact the problem of
homology in even the generalized reptilian carpus has not been com-
pletely solved. This is due partly to the fact that the carpal structure
of early tetrapods is quite variable (Homer, 1956, et al.). The pattern
found in rhachitomous amphibians, such as Eryops, is presently be-
lieved to be close to the ancestral type (Gregory, Miner, and Noble,
1923; Romer, 1956). In these amphibians four elements make up
the proximal carpal series, the radiale, proximal centrale, interme-



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 168

dium, and· ulnare (Fig:.lA).. The intermedium· and radiale are sepa-
ratedby the proximal centrale. A series of medial centrals (medialia)
extends from below the radiale'to below the. proximal centrale, and
between the proximal series and the distal carpals. For convenience
these centrals are usually distinguished as medialia · 1, 2, and 8. Most

mi?-*i,][jii{~4  -44774Al 0,/Oh

0 0~ . . - R #70
A B

~~pc+m 2.3 / r'~/=~~>

(C>f---Cot,1 Ok \ <~ LEL, \fl)0~ on 00 dE.27<I)0' OC g00
C D

FIcuRE.1. (A) The cirpus of a.primitive; generalized amphibian, such as Eryops
(modified from Homer, 1956). (B) The carpus of a primitive, generalized reptile
(modified from Homer, 1956). (C) The carpus of a pond turtle, genus Chrysemys.
(D) Hypothetical carpal pattern of a primitive tortoise.
Abbreviations: R - radius, U = ulna, r = radiale, pc = proximal centrale,
i = intermedium, u = ulnare, p - pisiform, m 1-3 - medialia 1-8, c 1-5 =~
carpals 1-5, I-V - metacarpals of digits one through five, me = metacarpal,
ph = phalange.



164 BULLETIN FLORIDA STATE MUSEUM Vol. 10

reptilian anatomists believe that medialia 2 and 3 were lost by the
time the early reptilian carpal arrangement had become Brmly estab-
lished (Romer, 1956). Mediale 1 is believed to have been lost soon
thereafter.

In the early feptilian carpal pattern the weight transmitted from
the radius is borne by the radiale and thence through the carpals to
digits one and two. Digit three is supported by the proximal cen-
trale and digits four and five by the ulnare. This arrangement permits
a more even distribution of weight through all the digits than does
the generalized amphibian type.

The pisiform makes its first appearance with the early reptiles,
where it is associated with the insertion of the M. ~exor carpi ulnaris.
It is present in some tortoises. When it is absent the tendon of the
#exor carpi ulnaris inserts on the surface of the sheet of connective
tissue that surrounds the carpus.

The carpal architecture of most tortoises is actually more easily
derived from the generalized amphibian type than that believed to
represent the earliest reptilian. arrangement. This is because the num-
ber and disposition of carpal elements in tortoises is similar to that in
generalized rhachitomes. Thus the differences between the carpus
of tortoises and generalized reptiles are probably only a matter of loss
and/or fusion of elements. Though phylogenetic evidence is lacking,
irrevocable structural data prove that in at least the tortoises, fusion
of carpal elements is much more common than loss. This proof is
founded partly on the fact that all stages of such fusion can be seen in
a selected series of certain species of tortoises, from two discreet ad-
jacent elements to adjacent elements fused in either the left or right
carpus and still divided on the other side, to complete fusion of the
same elements. Different degrees of fusion are occasionally seen be-
tween the right and left carpi of one individual. Furthermore, the
tendency to fuse increases with age; in several species the juveniles
and subadults often lack the fusion patterns characteristic of the
adults.

In addition t0 structural evidence suggesting fusion of carpal ele-
ments in tortoises, Hoffman's (1890) embryological studies have clear-
ly demonstrated the presence of two or more centers of ossification
in some elements that in the adult stage are represented by only one
large unit.

Though fusion of carpal elements is the commoner tendency in
tortoises, simple loss of elements also occurs. This is clearly the case
in the lack of ossification of the pisiform in some species or the loss
of a complete digit, as in Testudo horsBeldi.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 165

In at least the genus Go#herus, an additional element between the
radiale and intermedium articulates with the radius. This is interpre-
ted here as being homologous to the proximal centrale of the early
amphibians. Not only is the element in the same position, but it
functions in a similar manner. To my knowledge the proximal cen-
trale has not been reported previously in any other reptile genus.

The element usually referred to as the radiale in all Other tortoises
is undoubtedly the proximal centrale plus the radiale of more general-
ized amphibians. These two elements remain distinct in some species
of tortoises. The intermedium and ulnare of the testudinines are
probably h6mologues of those elements given the same names in
primitive amphibians. As in the rhachitomous amphibians, carpals
4 and 5 usually articulate with the ulnare, and carpal 8 articulates
with mediale 8. Carpals 1 and 2 have migrated inwards with the
loss of the hypothetical prepollex.

This interpretation, based mainly on the carpus of Gopherus, does
not modify the conclusions of others regarding the homology of the
generalized reptile or cotylosaur carpus, but simply suggests that the
variation in basic carpal patterns within the early reptiles was prob-
ably even greater than is generally presumed. An alternate, less ten-
able interpretation is that the element between the composite radiale
and the intermedium in tortoises is a new, additional central member,
not homologous to any found in the early reptiles or the Paleozoic
amphibians.

Another important feature of the carpus of Gopherus is that carpal
4 completely separates the ulnare from mediale 3. This pattern is
also found in the primitive amphibian carpus and is approached in
some of the early reptilian types. Ail these structural features suggest
that some of the tortoises may be less modified from a generalized
primitive amphibian or reptilian carpal arrangement, than is often
implied. Unfortunately no specimen of the earliest of fossil tortoises
(Geochelone?, Testudo, and Stylemus from Middle and Upper Eocene
deposits) has a c6mplete carpus, nor has a complete carpus been found
with the earliest fossil specimens ef the genus Copherus (Lower Olig-
ocene of central North America).

In reconstructing the primitive or pretortoise carpal pattern from
embryological evidence, from structural patterns of later fossil and
Recent tortoises, and from the evidence afforded by both normal and
abnormal conditions in modern species, one is led to the conclusion
that this carpus must have been composed of 12 elements distributed.
in three rows (Fig. 1, D), as in generalized rhachitomes. Below a
proximal series of four elements, the radiale, proximal centrale, inter-



166 BULLETIN FLORIDA STATE MUSEUM Vol. 10

m6dium, and uInare aligned side to side under most of the radius.
and ulna, must have been two elements, probably homologous with
medialia 2 and 8 of Romer (1956). Mediale 1 was already lost by this
stage, though it may·be represented by a small, medial subradial ele-
ment in less specialized genera'such as Pseudemys and Podocnemys.
Proximally mediale 2 articulated with the radiale and the proximal
central, and mediale 3 articulated with the proximal central and the
intermedium. Distally was a series of five carpals; proximally carpal
1 articulated with the. radiale, carpals 2,8, ·and 4.with the mediale 2
and 3 respectively, and carpal 5 with the ulnare.  Distal to the five
carpals were.five metacarpals. r A pisiform, .still' of common occur-
rhnce in diVelse turtle groups, was ~ probably present.

Following the, prbnary stages, the general trends of carpal evolu-
tion in the tortoises seem to have included (1). migration of subulriar
and subradial elements externally, (2) fusion of. subulnar and subradial
elements, and (8) fusion ofjmore distal elements (Fig. 2). Loss of
elements seems most frequent: at the external border of the carpus
below the outer edge of the-ulna. The same tendencies are observed
in the modification of the digital elements.as well.

~ R~U_~ j'R ~-Rtly/,1 -344

UOUVEU 00VOUL)
ABC

FIGURE 2. Major trends in the evolution of the tortoise carpus: (A) Fusi6n of
subradial elements. (B) Fusion of more distal eldments, fusion. of. proximal sub-
ulnar elements, and failure of carpal 4 to contact the intermedium. (C) Lateral
migration of subulnar and ,subradial elements and fusion of medialia.

The external migration of subradial and subulnar carpal elements
is apparently affected by the decrease of the proximal, sub-brachial
elements (radiale through ulnare), and the lipward rotation of the
lateral distal cakpals 1.and 5 until they come in contact with the
radius and ulna respectively (Fig. 2, C). This trend apparently be-
gins on either the internal or the external carpal surfaces, but never
on both at the same time. This is clearly shown in both fossil and
primitive living species of tortoi5es. Whether this migration initi-



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 167

ated on one surface Or the other seems to have phylogenetic import,
and the tortoise genera that show some form .of distal carpal migra-
tion can be divided into two major groups on other characters. Groups
that initiated carpal migration in one direction often migrate later in
the other direction as well. t

DESCRIPTIONS

Because of the complexity of the fusions and losses often observed,
the following accounts of the characteristic structure of the carpus of
each of the genera examined begin with the simpler arrangements
and proceed through progressively more complex and modified types.
Strict adherence to this arrangement is not possible in large, diverse
genera, such as Geochelone, which contain both primitive and ad-
vanced carpal types. Thus the sequence of taxa in the following
section is not meant to reflect phylogeny entirely. The classification
of living and extinct land tortoises proposed by Loveridge and Wil-
liams (1957) is followed throughout and commented upon under
"Phylogenetic Aspects."

Gopherus polyphemus (Daudin) (Fig. BA)

Thirty-two specimens from 105 t6 255 min in shell length were avail-
able for study (AMNH, MCZ, PPHM, UF, UMMZ, USNM). Except
for a slight difference in degree of fusion in digit 5, little variation
was observed from the smaller to the larger specimens. The proximal
centrale is present in all specimens examined; carpal 1 is fairly large
and articulates broadly with the radius; the radius is b'ordered below
by four elements (carpal 1, radiale + mediale 2, proximal centrale,
and intermedium); no intercarpal fusions are evident; the metacarpals
are typically fused to adjacent phalanges (14 of 82 specimens in all
5 digits, 18 in all digits except number 5); carpal 4 is wedged between
the ulnare and mediale 3, but not so extensively as in G. agassizii and
G. berlandieri; the pisiform is absent in all but 8 of the 32-specimens
examined; carpal 5, the ulnare, and intermddium are in broad con-
tact with the ulna.

Gopherus Bacomarginatus Legler (Fig. 8B)

Three specimens of this highly interesting, recently described
species of Gopherus were available for study (UF). The carpus is
similar to that of G. polyphemus, with 4 subradial elements (carpal 1,
radiale + mediale 2,- proximal centrale, and intermedium), and 8



0)\=ds«fee

xy- &97=3&*4{Y:A%*\
vevot}U
D

,,~ pc + i -CIn®C)* # 1 A~~+,5IRT11- 7~ ,;A

F
FIGURE 8. Carpi (diagramatic) of various tortoises: (A) Typical adult Cophefus
potyphemus. (B) Adult Gopherus Bat)omarginatus. (C) Juvenile Copherus agas-
Wzii. (D) Adult Gophents agassizii. (E) Juvenile Gopherus berlandieri. (F)
Adult Gopherus berlandieri.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 169

subulnar elements (intermedium, ulnare, and carpal 5); metacarpals
I through V are fused to the adjacent phalanges in all three specimens.

Gopherus agassizii (Cooper) (Figs, BC, SD)

Thirty-one specimens were available for study (MCZ, SNHM,
UCM, UF, UK). The arrangement of elements is different from those
of G. polyphemus and G. #avomarginatus and similar to that of G.
berlandieri. On the basis of difference in carpus structure, as well as
on a number of other anatomical features (True, 1892; Bogert and
Oliver, 1945; Legler, 1959; Legler and Webb, 1961), two species
groups may be recognized, the Polyphemus group containing G. poly-
phemus ·and G. #avomarginatus, and the Agassizii group containing
G. agassizii and G. berlandieri. The proposal by Wermuth and Mer-
tens (1961) that all four species of Gopherus are only subspecifically
distinct is untenable in view of present evidence which includes, be-
sides considerable anatomical data, the fossil history of. Gopherus in
the Pleistocene and important differences in habits: The view of
Grant (1960) that G. #avomarginatus may represent G. agassizii or a
subspecies thereof is strongly contradicted both by differences in
gross anatomical features (Legler, 1959; Legler and Webb, 1961) that
place them in different species groups, and by their carpal structure.

In 4 out of 8 specimens of Gopherus agassizii smaller than 150
mm, the proximal centrale is a separate element between the com-
posite radiale and the intermedium, as in the Polyphemus group. In
those small individuals in which the proximal centrale is absent, the
space it usually occupies is filled by the intermedium, suggesting that
the proximal centrale is fused with the intermedium in these speci-
mens. In 11 out of 23 specimens over 150 mm in shell length, the
proximal centrale is a separate element. In all 11 specimens with a
separate proximal centrale, carpal 1 is fused to the composite radiale,
while in all but 2 of the 12 specimens in which the centrale is fused
to the intermedium, carpal 1 is free and in contact with the radius.
Mediale 2 is fused to at least the radiale in 21 of the 23 specimens
over 150 mm, though in some of these the fusion is not quite com-
plete. No such fusion is manifest in 6 out of 8 specimens less than
150 mm in shell length. The radiale and medialia 2 and 8 are solidly
fused together in 11 specimens over 150 mm, and all these individ-
uals have carpals 1 and 2 also fused to this mass (Fig. 3D). Carpals
1 and 2 are fused tegether in 2I of the specimens over 150 mm. All
the metacarpals are firmly fused to the adjacent phalanges ih all speci-
niens examined, regardless of size. Carpal 5 is fused to both the, pisi-



170 BULLETIN FLORIDA STATE MUSEUM Vol. 10

form and ulnare in 18.of the 23 specimens over 150 mm; in every
larger individual in which carpal 5 is free, the pisiform is fused to the
ulnare. The pisiform is free in all smaller specimens examined.

The data above suggest that the carpus of Gopherus agassizii is
much more variable than that of G. polyphemus, particularly in the
lateral elements of the subradial and subulnar complexes.

Gopherus berlandieri (AgasSiz) (Fig. BE, 3F)

Thirty-seven specimens with an articulated carpus were available
for study (AMNH, MCZ, UCM, UF, UK), varying in ghell length
from 90 mm to 814 mm. The latter is the largest individual of this
species rep6rted so far.

The lack of a separate proximal centrale, plus a number of other
anatomical features suggest that Gopherus berlandieri is closer to
G. agassizii than to the other two species of Gopherus. This is sup-
ported by behavioral similarities within the two species groups.
Breeding has occurred in captivity between G. berlandieri and
G. agassizii (Mertens, 1956; Woodbury, 1952), but has not been dem-
onstrated between G. polyphemus and G. berlandieri, or G. Polyphe-
mus and G. agassizi.

In six specimens under 100 mm in shell length, mediale 2 is not
fused to the composite radiale as it is in all the larger specimens. In
none of the specimens is the proximal centrale separate from the
intermedium. Carpal 1 is separate and in contact with the radius in
all the specimens and is never fused to the composite radiale. While
metacarpals 3 and 4 are always fused to the adjacent phalanges, meta-
carpals 1, 2, and 5 are fused to the adjacent phalanges in only the
larger specimens. The pisiform is present in all specimens. Carpal
5 is fused to the ulnare in 22 of 41 specimens over 100 mm, and carpal
4 separates mediale 8 and the ulnare in all specimens. The radiale is
fused to mediale 2 in all individuals, and these are fused to mediale
8 in all adult specimens.

Stylemys nebrascensis Leidy (Fig. 4A)

The carpus of the North American Oligocene tortoise Stylemys
nebrascensis is known from an articulated foot in the collection of the
University of Michigan Museum of Paleontology. I have discussed
previously (1961) this important specimen which Case (1928) described
fully. The ridiale, proximal centrale, and medialia 2 and 8 are com-
pletely fused to one another; carpal 1 is separate and in contact with
the radius; the pisiform is missing (perhaps fused to the ulnare?);



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 171

and no fusion of the distal carpals to either metacarpalia or medihlia
is evident.

The carpus of this genus, as shown by the one articulated foot
known, represents one of the least modified carpal arrangements
known in tortoises. Thjs is to be expected in view of the unspecial-
ized structure of the rest of the skeleton and its early geologic age.

Geochelone emys (Schlegel and Muller) (Fig. 4B)
Only three adult specimens were studied (UF, VNHM, and ZSI).

The radiale, prokimal centrale, and medialia 2 and 8 are all firmly
fused to one another; carpal 1 is separate and in contact with the
radius, and therefore shares directly with the composite radiale the
weight transmitted through the radius to the medial digits; the
pisiform is separate in one specimen and fused to either the ulnare
or carpal 5 in the other two; carpal 5 is fused to the ulnare in all
specimens; carpals 1 through 4 and metacarpals I through V are
never fused to adjacent elements.

Except in its large composite radiale, this species seems to repre-
sent one of the more primitive of the known carpal arrangements.

Geochelone impressa (Gunther)
Only one subadult specimen of this species was available for study

(UF). Except for a lack of subradial fusion, the manus of this species
is practically identical to that of G. emys. The radiale, proximal cen-
trale, and medialia 2 and 8 are all separate. Carpals 1 and 5 are not
completely ossified, and are in contact with the radius and ulna re-
spectively. Carpal 5 is not fused to the ulnare, as in the larger speci-
mens of G. emys examined.

Geochelone radiata (Shaw) (Fig. 4F)
In the 8 adult specimens examined (AMNH, CNHM, and UF) the

carpus shows little fusion or loss of elements in comparison with other
species of tortoises. The composite radiale is composed of the radiale,
proximal centrale, and medialia 2 and 8 in 4 of the 8 specimens, and
of the radiale, proximal centrale, and mediale 2 in the remaining 4;
the pisiform is missing in all specimens; carpal 5 is in contact with the
ulna; carpal 1 is excluded from contact with the radius by the com-
posite radiale.

Geochelone travancorica (Boulenger) (Fig. 4D)
In the 18 adult specimens examined (UF) the carpus is simplified.

by the fusion of many of the elements. The composite radiale ist



R U

r,.| T ms ~~

07 O (g 4 37900
A

09»4«

47 « *1 0
0 0300

r.6 r+Pct\ ,~.Ii*
~ rn 2 11 m3 J- ,*4~X m2 + -iRT-*- )~„55~**«3~0 6) 0 « u

E F
FIGURE .4. Carpi (diagramatic) of various tortoises: (A) Stylemys nebrascenxis.
(B) Geocheione emys (G. impressa almost identical). (C) Geochelone radiata.
(D) Geochelone trat>ancorica. (E) Geochelone sulcata. (F) Geochelone pardaNs.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 173

made up of the radiale, proximal centrale, and medialia 2 and 3 in
15 specimens, and of the radiale, pr6ximal centrale, and mediale 2
in the remaining 3 individuals; the intermedium is always distinct;
carpals 1 through 5 are separate; carpal 5 is in broad contact with the
ulna; the composite radiale intervenes between carpal 1 and the radius;
metacarpals I through V are apparently fused to the adjacent pha-
langes; the pisiform is car,tilaginous in all specimens.

Geochelone sulcata (Miller) (Fig., 4E)

In the 6 adult specimens examined (UT-A and VNHM) the gen.
eral arrangement of the carpal bones is simple and like that in G.
radiata. Mediale 2 is fused to the composite radiale in 4 of the 6; the
pisiform is absent in all specimens; carpal 5 is not in contact with the
ulna, and with only the ulnare proximally; carpal 1 is excluded from
contact with the radius by the composite radiale; all remaining ele-
ments are separate.

Geochelone pardalis (Bell) (Fig. 4F)

In the 10 adult specimens examined (AMNH, CNHM, and UF)
many of. the carpal elements are fused. Mediale 2 is fused to the
composite radiale in 6 of the 10 skeletons; the pisiform is present in
all; carpal 4 is consistently fused to the ulnare; carpal 1 is fused to
carpal 2 in 8 of the 10 specimens; the metacarpals are never fused t6
their adjacent elements.

Geochelone elegans (Schoepff) (Fig. 5A)

The 17 specimens available for study (AMNH, UF, and ZSI) show
the carpus to be very similar to that of Geochelone pardalis. The
composite radiale in adults over 100 mm is composed consistently of
the radiale, proximal centrale, and mediale 2 and 8; in smaller speci-
mens mediale 8 is often separate;,the pisiform is present in all but
2 specimens; carpals 1 through 5 are always separate; carpal 5 is in
contact with the ulna; the composite radiale keeps carpal 1 from con-
tacting the radius; the metacarpals are never fused to adjoining b-ones.

Geochelone chiliensis (Gray) (Fig. 58)

In the 18 articulated forefeet available (UF) the carpus shows con-
siderable fusion. The intermedium is large; the proximal centrale
is never incorporated into the composite radiale; the latter is com-
posed of the true radiale and medialia 2 and 3; the ulnare is fused to



R U

\r + NE

~ A~ ~= ~~ 'B(fs t<'23
- «1\1r<-1+ pc·~_CU

f %4*.m 2 IE*/cs/ AdX m2+ -nr\T \

+ 3 AVO O

D~ 5 4

~  4~ +CI +(21 ~

0 0 0
F

FIGURE 5. Cami (diagramatic) of various tortoises: (A) Geochelone elegans,
(B) Geochelone chiliensis. (C)' Geochelone elephantopus. (D) Geochelon€ den-
ticulata. (E) Geochelone carbonaria. (F) Geochelone grandidieri.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 175

ments of its front foot show more fusion and atrophy than in any other
carpal. 5 in 8 specimens and distinct in the remaining 5; when fused
this composite element is in turn fused to carpal 8 in 7 specimens;
carpals 1 and 2 are fused to one another in all but 8 specimens; meta-
carpals I through V are never fused to adjacent elements; the pisi-
f6rm is absent in 8 specimens.

Geochelone elephantopus (Harlan) (Fig. 5C)

In the 18 adult specimens available (AMNH, CAS, SNHM, and
UF), the composite radiale is composed of the true radiale, the proxi-
mal centrale, and mediale 2. In larger specimens the true radiale is
often represented by a flat wedge of cartilage attached to the osseous
remainder of the composite radiale. Mediale 3 is always a distinct
element; the pisiform is usually cartilaginous; carpals 1 through 5 are
distinct, none are in contact with either the radius or ulna; the meta-
carpals are also distinct; digit three is so situated that its carpal is in
contact with both medialia 2 and 8, and both digits four and five
are in contact with the ulnare.

Geochelone denticulata (Linn.) (Fig. SD)

Ten specimenswere available for study (UF and VNHM). Though
the carpus is fairly conservative, the tendency to intercarpal fusion is
strong in this species. The composite radiale is composed of the
true radiale, the proximal centrale, and medialia 2 and 3 in all the
specimens except two, in which mediale 8 is a separate element; the
pisiform is always present; carpal 5 is fused to the ulnare and carpal
1 is fused to carpal 2; in two individuals carpal 8 is, in turn, fused to
carpals 1 and 2 on one side only.

Geochelone carbonaria (Spix) (Fig. SE)

In the 12 specimens examined (UF and VNHM) the carpus is very
similar to that of G. denticulata. In all specimens the composite
radiale is composed of the true radiale, the proximal centrale, and
medialia 2 and 8; the pisiform is present in eight specimens; carpal
5 is always fused to the ulnare; carpal 4 separates the composite radiale
and the ulnare; carpals 1 and 2 are fused in two specimens.

Geochelone grandidieri (Vaillant) (Fig. SF)

Whether the one specimen of Geochelone grandidieri (an extinct
Madagascar Pleistocene species) available for study (BMNH) is typical
of the carpus structure in this species is uncertain. The bony ele-



176 BULLETIN FLORIDA STATE MUSEUM Vol. 10

tortoise examined. The pattern differs greatly from that found in
other species of Geochelone and, if validated by additional material,
will strengthen the distinctness of the subgenus in which the species
has been placed.

The composite radiale is composed of the true radiale, proximal
centrale, medialia 2 and 3, and carpals 1 and 2. The inclusion of car-
pals 1 and 2 in the composite radiale is particularly noteworthy. Car-
pal 1 (in a fused condition) must have originally (juvenile condition?)
been in contact with the external lower border of the radius. Carpals
8 through 5 are separate, and 5 is in broad contact with the ulna; the
pisif6rm is present in the notch between the outer surface of carpal
5 and the ulna; the ulnare is in contact with the composite radiale;
metacarpals I through IV are fused with their adjacent phalanges.
The basic modification of the carpus of this species is fusion of ex-
ternally placed subradial carpals, metacarpal-phalangeal fusion in
all but the outer digit, and ventro-medial migration of the outer sub-
radial elements.

Geochelone gigantea (Schweigger) (Fig. 6A)
Six adult specimens were examined (AMNH and UF). The com-

posite radiale is composed of the true radiale, proximal centrale, and
mediale 2; digit three makes contact with both the composite: radiale
and mediale 3, digit four makes contact with mediale 8 and the ulnare;
carpals 1 through 5 are discreet, and neither 1 nor; 5 makes contact
with the radius or ulna; the metacarpals are never fused to adjacent
elements; the pisiform is represented by a block of cartilage only.

Psammobates oculifera (Kuhl) (Fig. 6B)
One specimen was available for study (VNMH). The composite

radiale is composed of the true radiale, proximal centrale, and medialia
2 and 3; carpal 5 is fused to the ulnare; the pisiform is absent; car-
pal 4 separates the ulnare and the composite radiale; carpals 1,2, and
8 are all fused to one another. Hewitt (1987) states that the inter-
medium and ulnare are fused in one of his adult specimens, as are
metacarpal V and the proximal phalange. I did not find these fusions
in the Vienna Museum specimen.

Homopus areolatus (Thunberg) (Fig. 6C)
Eight specimens were examined (UF, VNHM). The presence of

only four toes on the front feet of this species is notable. Hewitt
(1937) believed digit one to be the missing toe. I believe digit five



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 177

has disappeared, on the basis of (I) the normal articulation of digits
one and two with the composite radiale, (2) the normal articulation of
digit three with the unfused mediale 8, (8) the separation of the com-
posite radiale and the ulnare by mediale 8 and (4) the fact'.that only
one digit artie#ulates with the ulnare.

The cgmposite radiale is comprised of the 'true radiale, proximal
centrale, and mediale 2; mediale 8 is always discreet; carpals 1 through
4 are fused to the adjacent metacarpals; carpal 5 may be fused to the
ulnare. No pisiform is present.

Homopus signatus (Schoepff)
No specimens of this species were examined in the present study

and the following descripti6n is based on that by Hewitt (1987). Five
toes are always present; the composite radiale is composed of the
true radiale and proximal centrale; the intermedium is small but dis-
tinct; mediale 2 is separate; mediale 8 has apparently moved dorsally
to articulate with the ulna, pushing the small ulnare laterally; the
pisiform is present; carpals 1 and 2, and 4 and 5 are fused (as in
H. femoralis, according to Hewitt, Ibid); metacarpals I through V
seem t6 have fused to their adjacent phalanges.

Puxis arachnoides Bell (Fig. 6D)
Only two specimens of this interesting tortoise were examined

(VNHM). The composite radiale is composed of the true radiale, the
proximal centrale, and medialia 2 and 3; the ulnare is separate but
small; carpal 5 is in broad contact with the ulna; carpals 1,2, and
metacarpal I are all fused together; the mediale 8 portion of the com-
p6site radiale is in contact with the ulnare, thereby excluding carpal
4 from articulation with the intermedium. The remainder of the
elements comprising the foot are unmodified.

Chersine ahgulata (Schweigger) (Fig. 6E)
Ten specimens were studied (UF). The carpus of this odd tor-

toise is unlike that of any other species examined. Most notable is
the very small intermedium with a large proximal centrale lying com-
pletely under it and making contact with the very large ulnare; the
composite radiale is pr6bably composed of the true radiale and medi-
ale 2, mediale 3 is very large and articulates with the proximal cen-
tale dorsally, the ulnare externally, and. both carpals 3 and 4 distally;
carpal 4 articulates with both mediale 8 and the ulnare. The remain-
ing elements and their positions are normal.



178 BULLETIN FLORIDA STATE MUSEUM Vol. 10

Kinixys homeana Bell (Fig. 6F)

In all members of this genus the carpus is most unusual in that
the radius projects farther distally beyond the ulna than in other tor-
toises. The consequent shifting of the carpal elements makes their
homologues so difficult to determine that the following interpretations
for the Kinixys species are entirely tentative.

Four specimens of K. homeana were available for study (UF).
The intermedium is very large, as is the discreet adjacent ulnare; the
composite radiale is composed of the true radiale, the proximal cen-
trale, and medialia 2 and 8, carpal 5, though small, is discreet and in
contact with the ulna proximally and the ulnare medially. The dorsal
shift of this element brihgs the elongated metacarpal V even with
carpal 4. Carpals 1, 2, and 8 are discreet, and the latter has migrated
slightly laterally to articulate with carpal 4 as well as its normal articu-
lation with the mediale 8 portion of the composite radiale. The prox-
imal phalange of digit five is elongate to accommodate the proximal
migration of its corresponding carpal and metacarpal units. The
pisiform is absent. The remaining elements are normal.

Kinixys erosa (Schweigger) (Fig. 7A)

Two specimens Were studied (UF and VNHM). The carpal ar-
rangement is slightly more modified than that of Kinixys homeana.
The composite radiale is composed of the true radiale, the proximal
centrale, and mediale 2; mediale 8 is discreet and in its normal posi-
tion; the intermedium is very large; carpal 5 is fused to the ulnare;
carpal 3 is probably fused to metacarpal III. The pisiform is absent.
The remaining elements are normal.

' Kinixys belliana Gray (Fig. 78)

In the six specimens available (UF) the composite radiale is com-
posed of the true radiale, the proximal centrale, and medialia 2 and
3. As in the other species of the genus the intermedium is large and
located high in the proximal series; the composite ulnare is composed
of the true ulnare and carpal 5; carpals 1 and 2 are fused together, as
are carpal 4 with metacarpal IV and metacarpal V with the most prox-
imal phalange of digit five; carpal 8 is only a thin wedge of bone, but
in its normal position; no pisiform is present. Some specimens have
only 4 toes (Schmidt, 1919). The missing toe is usually five (Hewitt,
1987), but may be four in some specimens (Loveridge and Williams,
1957).



R U
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0 «COOUE
A U <~ 8

AFTSC'>X,- 1(on
A~~~~m 3 1~~~:Ch C 02*m2 + -V/(5)/5.;~N*fs:(42

Oug
C D

JU JU

E
FIGURE 6. Carpi (diagramatic) of various tortoises: (A) Geoche?one gigantea.
(B) Psammobates oct@era. (C) Homopus areolatus. (D) Pyxis arachnoides. (E)
Chersine angulata. (F) Kinixus homeana.



180 BULLETIN FLORIDA STATE MUSEUM Vol. 10

Testudo graeca Linn. (Fig. 7C)

Twenty-one adult specimens were studied (UF and VNHM).
Thompson's (1982) plate 28 is in error in showing three Pbalanges for
this species. The composite radiale is composed of the true radiale,
the proximal centrale, and medialia 2 and 8 in 16 specimens, of the
radiale, proximal centrale and only mediale 2 in 5 specimens; carpal
4 is excluded from contact with the intermedium by the lateral exten-
sion of the composite radiale in all individuals; carpals 1 and 2 are
fused; the pisiform is present; the ulnare includes carpal 5 from artie-
ulation with the ulna; the composite radiale includes carpal 1 from
articulation with the radius; metacarpal 1 is often fused to the prox-
imal phalange, an individual characteristic according to Siebenrock
(1906) which this study confirms.

Testudo hermanni Gmelin

Eighteen specimens were examined (UF and VNHM). As the
carpus of this species is apparently identical to that of Testudo graeca,
no description or illustration seems necessary.

Testudo marginata Schoepff (Fig. 7D)

Three specimens were stildied - (VNHM). The composite radiale
is composed of the true radiale, the proximal centrale, and medialia
2 and 3; the intermedium is fused to the ulnare in both carpi of one
individual and fused on only one side in another; the pisiform is pres-
ent in all the carpi studied; the ulnare excludes carpal 5 from articu-
lation with the ulna; carpals 1 and 2 and metacarpal 1 are fused into
a solid mass in one specimen; carpal 1 contacts the radius.

Testudo horsfieldi Gray (Fig. 7E)

Four specimens were examined (BNHS and UF). The presence
of only four toes in the manus makes it difficult to determine homolo-
gies. Digit four is probably the lost one. The composite radiale is
composed of the true radiale, proximal centrale, and mediale 2; medi-
ale 3 is probably fused with carpals 8 and 4; the composite ulnare
probably formed of the true ulnare and carpal 5; carpal 1, which is
in contact with the radius, is fused to metacarpal I; digit two is nor-
mal; metacarpal III and its adjacent phalange are fused in two speei-
mens and free in the other two; metacarpal V(?) is apparently fused
to its adjacent phalange in three individuals.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 181

Testudo kleinmanni Lortet (Fig. 7F)

Two specimens of this tortoise were studied (VNHM). It is
known sometimes to have only four toes (Flower, 1988). The com-
posite radiale is composed of the true radiale, proximal centrale, and
mediale 2 in both specimens; carpal 1 is in contact with the radius
and is also fused to carpal 2; the ulnare excludes carpal 5 from con-
tact with the ulna; no pisiform is present; metacarpals IV and V are
fused to their respective adjacent phalanges. Perhaps one of the
most unusual features of this carpus is that metacarpal I is also in
contact with the radius.

FummONAL ASPECTS

As Homer (1983) points out, the way a turtle moves its limbs is,
despite the presence of the shell, probably as close to that of the
primitive tetrapod method of locomotion as can be found among
living reptiles. In tortoises the well-developed humerus head is at-
tached to the shaft by a constricted neck, and is oriented more me-
dially to the shaft than dorsally. The articulating surface of the head
shows considerable interspecific variation in shape, from almost  hemi-
spheric in a few species to ovate with the long axis horizontal in most.
The so-called glenoid cavity of the tortoise shoulder girdle is similarly
shaped to accommodate it. Strofigly ovate articulating surfaces (the
usual case in species with narrow shell openings) restrict limb move-
ment to the horizontal plane and greatly limit vertical movement.

Of the two elements comprising the brachium, the radius is usually
the longer and more slender. Both are often in broad contact near
their distal ends, where strong ligaments and muscles bind them tightly
together. Torsional movement may be further reduced by an inter-
digitating articulation between the two elements at their distal ends.

The restriction of the movement of the humerus to the horizontal
plane, the reduction of rotation in the brachium, and the fusion of
many of the carpais and metacarpals all limit movement to those
planes where shell shape permits it. Some distal movement is ob-
viously necessary, because when the Rexor musculature pushes the
foot against the ground the brachium and carpus serve as a sort of
stationary pivot on which the humerus rotates. The great structural
variation in the degree of fusion in the elements comprising the car-
pus of tortoises is apparently related to (1) reductfon of mobility in
certain areas, and (2) failure of the component elements to serve a
definite mechanical need.

The ulna makes the most extensive articulation with the humerus



R U

1 ' +CS
-1 1 h u+ (51 =Iln /2\

A-- , CC33\ (4+\ < ~

B«809-

0 00Voei '- I-

C D

/cit \\ r+pcj C\\r + PC f<5_J

Af z )\ *mg//iaTA.,U J

»

0O F~~E
FIGURE 7. Carpi (diagramatic) of various tortoises: (A) Kinixys erosa, (B)
Kinixys belliana. (C) Testudo graeca (Testudo hennanni almost identical). (D)
Testudo marginata. (E) Testudo kleinmanni.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 188

and is certainly the major weight-bearing element of the upper
brachium. Atthe beginning of the propulsive phase the foot is placed
on the ground in such a way that the radius bears all the weight,
which is then transferred gradually to the ulna as the body moves
forward and the limb pivots inward. This shift is accomplished by
certain muscles, particularly M. interosseus brachis.

03 00 -
[3355>~CS« CtAB

FIGURE 8. Cross sections of digit three and. the carpus through the intermedium
of, (a) Geochelone radista, an essentially plantigrade genus, (B) Kinixgs homeana,
a digitigrade genus, and (C) Gopherus poll/Phemus. an unguligrade genus.
Abbreviations: I = intermedium, P = proximal centrale, C = carpal, M =
metacarpal, P. = penultimate phalanyx, U = unguinal phalanyx.

As pointed out above, the considerable variation in the tortoise
manus is due principally to the fusion of elements. That of the genus
Stylemys, which represents one of the earliest fessil tortoises known,
shows a primitive pattern both in the number of elements and in their
relative positions. In Stylemys and in the extant genus Geochelone,
most of the weight is transferred to the substrate through the carpals.
These elements are usually thickened ventrally where they rest on a
thick cushion of connective tissue and enlarged dermal scutes, and
they bear all the weight as the metacarpals and phalanges extend
forward at almost right angles to the brachial axis. Tortoises with
this arrangement are essentially plantigrade. The extent of the fleshy
cushion between the carpals and the substrate Varies between speeies.
In true digitigrade forms the penultimate phalange transfers the
weight to the substrate and is thickened ventrally. Of all the tor-
toises only the genus Gopherus is truly unguligrade (Fig. 8). Whether
or not the early members of the genus were also unguligrade is un-
known.

In most genera of tortoises, as the foot moves forward into its new
position during locomotion digits two and three usually provide the



184 
BU

LLETIN
 FLO

R
ID

A STATE M
USEUM

C ._C If f~'-----~rxh~ -r~>~~-)~f-\C,)A
«.22* I

-1,4 h--\. L -/ littlliz '*8 1,<Al .2---/4 7 ~-// 2-

B U* -/flis'Olittaby & 2507-

C. ~~ D ELBOW»/---1

l.·
654321 TOE_~"7

7 6 54 3 21 <
FIGuRE 9. Movenient of the front limbs during locomotion, (A) Geochelone,adiata, (B) Gopherus poll,phemus. (C) Positions 2
of front right limb of Geochelone radiata during propulsion (solid lines) and retrieval (dotted lines), (D) Same, Copherus poly- 5
phemus. A to D all prepared from slow-motion photographs.



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 185

final propulsive force. This is indicated by analysis of slow motion
photography and reflected in wear patterns on the toenails.

Tortoises have'two major patterns of limb positions and movement
during walking, 6ne represented by Geochelone, the other by Goph-
erus. In Geochelone radiata the distal end of the humerus describes
an oval with its major. axis at approximately 45° (Fig. 9A, 9C). The
ulna and radius rotate but little on the humerut, except near the for-
ward part of the arc, when the brachium rotates slightly outward.
The arc of the moving humerus and the relative immobility of the
brachio-humeral articulation bring the foot d6wn with the toes di-
rected slightly inward. At this point the humerus rotates anteriorly on
the radio-ulnar articulation, moving the body slightly upward and
fofward.

As the body continues its forward motion, the weight is slowly
transferred from the radius to the intermedium and then to the sub-
ulnak elements. The foot continues to rotate so that the toes face
even farther inward. The weight is now transferred to the ulna as
the forward-moving body rolls the foot until digits one and two are
lifted off the ground at the end of the propulsive phase. The retrieval
phase begins as the weight is transferred to the opposite forelimb,
now near the end of its retrieval phase. Its propulsive phase is trig-
gered by a shift of gravity to that side of the body, accomplished by
(1) the weight of the laterally suspended limb moving into its new
position, (2) the fiexion of the opposite hind limb, and (8) the lateral
force of the front limb still on the ground near the end of its cycle.

Geochelone has two major planes of flexure at the carpus, at the
metacarpo- and brachio-carpal junctures. Kinesis in both flexures is
most pronounded neaf the end of the propulsive cycle, when the. toes
are directed inward and at almost right angles to the brachium. In
most plantigrade tortoises the intermedium is below the brachio-cafpal
flexure, but in the more digitigrade types such as .Kinixys, the inter-
medium lies above the fle*ure. The small size of the intermedium in
Kinixys and its position permit m6re rotation at the brachio-carpal
juncture than in most species of Geochelone.

In the second major locomotor pattern, exhibited only by the un-
guligrade Gopherus, the lower limb passes through a broader oval
than in Geochelone (Fig. 9B, 9D). Though the propulsive phase is
somewhat shorter, the body is lifted higher and farther forward. The
lower leg is oriented m6re vertically throughout the entire sequence,
probably largely «because of the relative immobility of the carpus.
Most important, the foot is rotated outward rather than jnward during
the pfopulsive phase, and to a much greater degree than in Geoche-



186 BULLETIN FL0RIDA STATE· MUSEUM- , · Vol. 10

lona- Both the greater vertical movement of the distal-end of the
humerus and the greater rotation of the brachium in Gopherus are
accomplished ·largely. at the proximal head of the humerus, whith is
much more nearly spherical than that of most species of Geochelone
dr Kinixys. These two genera depend for vertical limb movement on
the-humero-ulnar joint, Which. is much more.flexible than in Gopherus.

PHYLOGENETIC ASPECTS

In the -more  primitive fortoises 12 elemehts, including the pisi-
form, comprise the carpus. The reduction' in the number of elements
in more advanced tortoises ·is probably in response to stresses placed
on the carpus during locomotion.

The radius, which receives the initial shock of sudden weight sup-
*64 durin* the propulsive phase, must transfer this weight to both
the ulna and the subradiai elements-. In the primitive tort6ise carpus
the weight is transferred to four sub'radial elements (carpal 5, radiale,
#roximal centrale, and intermedium), thence to five more distal ele-
ments (carpals 1,2,8, and medialia 2 and 3). During this phase a
number of important shearing forces develop between the subradial
elements. In more advanced forms some of the subradial elements are
usually fu5ed into a composite radiale (radiale + proximal centrale +
mediale_2), and-carpal_1 is no longer in contact with-the radius. This
arrangement solidifies the carpus and makes it less flexible in the
area of greatness stress by reducing the total number of potential in-
teracting surfaces. A similar reduction in subulnar articular surfaces
through fusion occurs in some advanced forms as well, thouth never
as extensively as in the subradial series. The subulnar articular re-
duction is apparently related to shearing. forces operative during the
middle and last parts of the propulsive phase, when the ulna bears
much of the weight of the front paft 6f the animal.

In the most advanced forms this subfadial modification is carried
e>en further, so that carpal 1 may fuke to the composite radiale. Met-
acarpals i and II, and sometimes even III also fuse into one large
mass, and carpal 5 may fuse to carpal 4. Thus the number of carpal
and metacarpal ,elements is reduced from 12 elements in the most
primitive condition to 5 in the most simplified condition known. The
most extreme degree of fusion and loss known so far in tortoises oc-
curs in the extinct Pleistocene species Geochelone grandidieri (Fig.
5F).

When the carpal structures of the major groups of living and ex-
tinct tortoises are compared, a heirarchial system 6f increasing or de-



1966 AUFFENBERG:  CARPUS 'OF· LAND'',TORTOISES 187

creasing complexity becomes evident.:.Thdt the, direction of the se-
quence is -toward. simplicity is, suggested by the artangements found
in the earlier fossil-.tortoiies such. as. Stylemyrand in, such presumed
primitive groups of extant gdnerii as the subgenus Manouria of the
genus,Gedchelone. : It is. also reflected by the development of the car-
pus in living species. 3

In the major stages in the evolution of.the tortoise carpus, the  Brst
(Fig. lD) is represented by the primitive condition of three subradial
and two subulnar elements. In the next stage (Fig. 2A) various sub-
radial elements fuse, different ones in different phyletic lines. This
is apparently followed (Fig. 2B) by fusion of subulnar elements, of'
carpals, and of metacarpals with phalanges. The last stage (Fig. 2C)
involves the movement outward of both carpals 1 md 5, so that they
contact the radius and ulna respectively. The eventual development
of carpo-brathial contact on both sides' is derived independently in
two phyletic lines. -

The phyletic scheme proposed by Loveridge and Williams (1957)
based largely on shell structure (Fig. 10) corresponds remarkably well
with one based on carpal structure (Fig. 11). The only areas of dis-
agreement between the two schemes are in the posifions of the sub-
genus Aldabrachelys and the genus Chersine.

The genus Gopherus, as pointed out previously, exhibits a primi-
tive carpal pattern, though the manus is highly specialized for dig-
ging. The foot and entire lower leg are flattened antero-posteriorly.
More important, carpus flexion is reduced by both the flattened articu-
lar surfaces of the carpal elements and by a strong ligamentous  sheet
over the entire carpus and adjacent brachium. Of all the extant
genera of tortoises, it is the only one that is completely unguligrade.

Perhaps the most important single character of phylogenetic sig-
nificance is the position of carpal 4. In Geochelone pardalis and
G. elegans of the subgenus Geochelone, all species of the subgenus
Chelonoides and of the genus Gopherus, carpal 4 contacts the inter-
medium and separates the ulnare and mediale 8. In all other tor-
toises the ulnare contacts mediale 3, and carpal 4 fails to contact the
intermedium. On the basis of the position of carpal 4 in the general-
ized amphibian and reptilian carpus, the more primitive arrangement
is a contact with the intermedium. Unfortunately, no articulated
carpus is available for the primitive, extinct subgenus Hadrianus.
Carpi of this subgenus and of earlier fossils of the genus Stylemys
than are now available can be expected to show a contact between
carpal 4 and the interniedium.

On the basis of carpal structure, the species of the Neotropical sub-



188 BULLETIN FLORIDA STATE MUSEUM Vol. 10

genus Chelonoides seem least modified from the presumed primitive ~
condition, with Geochelone pardalis and G. elegans of the subgenus
Geochelone only slightly more modified. The carpi of the remaining
taxa represent a complex of specializations, often indepehdently de-
rived, and from which few phylogenetic conclusions can be drawn.
The carpus of Kinixys seems to represent the greatest deviation from
the presumed primitive condition.

PSAMMOBATES MALACOCHERSUS

HOMOPUS
TESTUDO

KI N IXYS

CHERSINE ~ ~STYLEMYS

PRIMITIVEPYXIS
~ TESTUDININE ~GOPHERUS

ACINIXYS

+Hadrianus

Asterochelys-~
Indotestudd Manouria

Geochelone

Chelonoides GEOCHELONE

Aldabrachelys

FIGURE 10. The hypothetical relationships of tortoises based on shell characters
(modified from Loveridge and Williams, 1957).



1966 AUFFENBERG: CARPUS OF LAND TORTOISES 189

PSAMMOBATES MALACOCHERSUS I

HOMOPUS ~

CHERSINE ~
 TESTUDO

KINIXYS A A 
con ~~

 ~STYLEMYS
6 9

o ontact c4-1
R/c 1 U/c5

PYX I S ,--~h
:v PRIMITIVE ~
2 TESTUDININ ~ GOPHERUS

ACINIX¥§/ ~

Asterochelys

Aldabrachelys

Chelonoides
Indotestudo

Geochelone Geochelone
(sulcata) (pardalls and elegans)
GEOCHELONEManouria

FIGURE 11. The hypothetical relationships of tortoises based on carpal archi-
tecture. Abbreviati6ns: R = radius, U = ulna, c = carpal (1,4 or 5), i = inter-
medium, / = no contact between radius or ulna and carpals 1 or 5, no slash
represents contact of elements.



190 -BULLETIN FLORIDA STATE MUSEUM Vol. 10

LITERATURE CITED
Auffenberg, W.

1961. A correction concerning the phalangeal formula of the turtle Stutem!/s
nebrascensis Leidy, Copeia (4), 1961: 496-498.

Bauer, G.
1885. Zur Morphologie des Carpus und Tarsus des Reptilian. Zool. Anz:,

82681-638.
1888. Beitrage zur Morphogenie des Carpus und Tarsus der Vertebraten.

Fischer, Jena. pp. 1-86.

Bobert, C. M., and J. A. Oliver
1945. A preliminary analysis of the herpetofauda of Sonora. Bull. Amer. Mus.

Nat. Hist., 88(6): 303-425.

Bojanus, L. H.
1819. Anatomie -Testudinis europeae. Vilnae. pp. 1-126.

Case, E. C.
1928. A specimen of St!)lemys nebrascensis Leidy, with the bones of the feet

and limbs. Contrib. Mus. Paleon., Univ. Mich., 5(6): 69-78.

Dollo, L.
1929. Carpus und tarsus. Roux's Archiv., 102: 272-298.

Flower, S. S.
1924. A remarkable tortoise of the genus Testudo. - Proc. Zool, 'Soc. London,

pp. 920-921.
1938. Notes on the Recent Reptiles and Amphibians of Egypt. Proc. Zool.

Soc. London, pp. 745-851.

Gegenbauer, C.
1864. Untersuchungen zur vergleichenden Anatomy des Wirbelthiere. I.

Carpus und Tarsus. Leipzig. pp. 1-127.

Grant, C.
1960. Gopherus. Herpetdlogica 16(1): 29-81.

Gregory, W., R. W. Minor, and G. K. Noble
1928. The carpus of Ervops and the structure of the primitive chiropterygium.

Bull. Amer. Mus. Nat. Hist., 48(10) 279-288.

Hartmann,Weinberg, A.
1929. .Ober Carpus und Tarsus der Pareiasauriden.. Anat. Anz., 67: 401-428.

Howitt, M
1937. A note on the relationships of the Cape genera of land tortoises. South

African Journ. Sci., 88: 788-796.

Hoffman, C. K.
1890. (in Bronn) Klassen und Ordnungen des Thier-Reichs. Reptilien, I.

Schildkr6ten. Leipzig, pp. 1-464.



1966 AUFFENBERG: 'CARPUS OF LAND TORTOISES 191

Howell, A. B.
1985. Primitive carpus. Journ. Morph., 57: 105-112.

Legler, J.
1959. A new tortoise, genus Gopheus from north-central Mexico. Univ. Kan-

sas Publ., Mus. Nat. Hist., 11(5): 885-848.

Legler, J. M., and R. G. Webb
1961. Remarks on a c611ection of Bolson tortoises, Gopherus flavomarginatus:

Herpetologica, 17(1): 26-37,

Loveridge, A., and E. E. Williams
1957. Revision of the African Tortoises and Turtles of the suborder Crypto-

dira. Bull. Mus. Comp. Zool., 115(6): 168-557.
Mertens, R

1956. Uber reptilien-bastarde, II. Senck, Biol., 87: 888-894.

Mertens, R., and H. Wermuth
1955. Die rezenten Schildkr6ten, Krokodile und Bruckenechsen. Zool.  Jahrb.

Syst.; 88: 828-440.

Nauck, E. T.
1924. Die Beziehungen zwischen Beckenstellung und Gliedmassenstellung bei

tetrapoden Vertebraten. Morph. Jahrb. 53.1-47.

Rabl, C.
1916. Uber die Muskeln und Nerven der Extremitblen von Iguana tuberculata

Gray. Anat. Hefte., 53: 688-789.
Ribbing, L.

1909. Die Unterschenkel-und Fussmuskulatur der Tetrapoda. Act. Univ.
Lund., 5: 1-158.

Romer, A. S.
1983. Vertebrate Paleontology. Univ. Chicago Press, Chicago, pp. 1-491.
1956. The asteology of reptiles. Univ. Chicago Press, Chicago, pp. ·1-772.

Schaeffer, B.
1941. The morphology and functional evolution of the tarsus in amphibians

and reptiles. Bull. Amer. Mus. Nat. Hist., 78(6): 895-472.

Schmidt, K. P.
1919. Herpetology of the Belgian Congo, Pt. I. Turtles, Crocodiles, Lizards

and Chameleons. Bull. Amer. Mus. Nat. Hist., 89: 385-624.

Shah, R. V., and V. B. Patel
1964. Myoloby of the chelonian pectoral appendage. Journ. Animal Morph.

and Physiol:, 11(1): 58-84.

Siebenrock, F.
1906. Schildkr6ten von Ostafrica und Madagascar. (In Voeltzkow, Reise in

Ostafrika in dem Jahren (1908-1905). Stuttgart. 2: 1-40.



192 BULLETIN FLORIDA STATE MUSEUM Vol. 10

Sieglbaurer, F.
1909. Zur Anatomie des Schildkr6ten-extremittiten. Arch. f. anat, u, Phys.,

Anat. Abt., pp. 188-280.

Sj6gren, S. J.
1940. Die Entwicklung des Hand-und Fuss-Skelets bei Chamaeleon bitaeniatus

Elliott. Morph. Jahrb., 85: 248-260.

Steiner, H.
1920-1. Hand und Fuss der Amphibien, ein Beitrag zur Extremitaten frage.

Anat. Anz; 58: 518-542.

Thompson, J. S.
1932. The anatomy 6f the tortoise. Proc. Roy, Dublin Soc., 20(28): 359-427.

True, F. W.
1892. Key to the three species of North American land tortoises. Proc. U. S.

Nat. Mus., 4: 484.

Walker, W. F.
1947. The development Of the shoulder region of ·the turtle Chfusemus picta

marginata. Journ. Morph., 80: 195-249.

Wermuth, H.; and R. Mdrtens
1961. Schildkr6ten, Krokodile und Bruchenschsen. Jena. pp. 1-422.

Wiedersheim, R.
1876. Die altesten Formen des Carpus und Tarsus des heutigen Amphibien.

Morph. Jahrb. II., pD. 421-433.

Williston, S. W.
1914. The osteology of some American Permian Vertebrates. Journ. Geol.,

22(4): 864-419.
1925. The Osteology of the Reptiles. Harvard Univ. Press: Cambridge. pp.

1-299.

Woodbury, A. M.
1952. Hybrids of Gopherus berlandieri and C. agassizii. Herpetologica, 8:

38-86.



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