Download Full Document - Mountain Boomer Music!

BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY
Fig. 17. -Ventral view of the fifth metatarsal bone of Crotaphytw
collaris showing the contact of the medial and lateral plantar
tubercles forming an arch (redrawn from Snyder, 1954).
may be referring to ventromedial curvature). They
may have been refemng to the presence of a pro-
portionally shorter and broader pelvic girdle in east-
em populations of Crotaphytus collaris (the only
representative of the "collariform" group that they
examined) than in other Crotaphytus species or
Gambelia. This difference appears to be related, at
least in part, to modification of the pubic rami, which
are nearly transverse in orientation, rather than
acutely angled anteriorly. However, the condition
in the remaining populations of C. collaris (formerly
referred to C. c. fuscus, C. c. baileyi, and C. c. au-
riceps) appears to be intermediate in each of these
features. Coding of this variation is further com-
plicated by individual variation in pelvic girdle
structure, such that some individuals approach the
eastern C. collaris condition, while others approach
the condition of other Crotaphytus species. Short,
broad pelvic girdles are often observed in crevice-
dwelling species (e.g., Sauromalus) and the rela-
tively short, broad, pelvic girdles of eastern C. col-
laris may be related to the crevice-dwelling behavior
observed in these lizards.
LIMBS
(Character 47; Fig. 17)
On the plantar surface of the fifth metatarsal are
two large tubercles termed the medial and lateral
plantar tubercles by Robinson (1975). These tuber-
cles serve as attachment points for the tendons of
M. gastrocnemius. In the majority of iguanian spe-
cies, a groove runs between the two tubercles and a
NO. 32
tendon of M. flexor digitorum longus passes within
it (Robinson, 1975). In Crotaphytus. the medial
plantar tubercle usually curves laterally such that it
contacts the lateral plantar tubercle forming a complete
arch (Fig. 17), through which passes the tendon
of M. flexor digitorum longus (noted and figured by
Snyder, 1954). The contact ofthe tubercles is usually
extensive and in some individuals, the tubercles may
fuse completely. The arch condition was absent in
the entire available series of Gambelia (41 specimens)
and, in adults, it was always present in the
20 C. bicinctores, four C. antiquus. 12 C. dickersonae,
five C. gristneri, and 22 C. vestigium examined.
It was complete on at least one pes in 28 of 36 C.
collaris, three of five C. insularis, i 1 of 12 C. nebrius,
and six of seven C. reticulatus. The majority of specimens
that lacked the complete arch were juveniles,
and in most cases the gap between the medial and
lateral plantar tubercles was narrow. Therefore, this
character was scored only for adults. Among the
outgroup taxa examined, the arched form of the
medial and lateral plantar tubercles was present only
in the phrynosomatid sand lizards (Uma, Callisau-
rtcs, Cophosaurus, and Holbrookia). This feature ap-
pears to represent a synapomorphy for Crotaphytus,
as well as providing additional character support for
the monophyly of the phrynosomatid sand lizards.
The hindlimb of Crotaphytus is much longer than
that of Gambelia of similar SVL. A relatively long
hindlimb is typical of lizard species that utilize bi-
pedal locomotion (Snyder, 1952, 1954, 1962), al-
though agamines provide an interesting exception.
Much of the variation in hindlimb length between
Crotaphytus and Gambelia is realized in the longer
crus of the former, while the pes appears to be of
relatively similar length. Although a greater relative
hindlimb length appears to be a derived character-
istic of Crotaphytus, there is great variation in the
outgroup taxa and this feature was not included in
the phylogenetic analysis.
The dorsal body squamation of Crotaphytus and
Gambelia is remarkably similar in that both genera
are characterized by relatively undifferentiated head
scales and fine homogeneous dorsal body squama-
tion. However, despite many similarities in scale
patterns and scale sizes on the various regions of
the body, phylogenetically useful variation in squa-
mation exists. A more detailed description of the
squamation of crotaphytids is provided in the tax-
onomic accounts of the family, genera, and species.