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1996 McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 2 7
(Fig. 16). They were separated in one of four C.
antiquus, in all specimens of G. copei and G. silus,
and in at least ten of 15 G. wislizenii. However, in
those five specimens of G. wislizenii in which the
second ceratobranchials were in contact, the contact
may have been an artifact of preparation. Separated
second ceratobranchials are relatively rare in igu-
anians and were only observed in Uta stansburiana,
some Petrosaurus mearnsi, Phrynosoma asio, some
Uma exsul, some Brachylophus fasciatus. Phyma-
turus, some Leiolepis belliana, and Enyalius bili-
neatus. Separated second ceratobranchials was con-
sidered to be the derived state within Crotaphytidae.
However, this character could not be evaluated in
many outgroup taxa because the hyoid apparatus is
often damaged in preparation and this polarity as-
sessment should only be considered tentative.
SkuN Rugosity (Character 37). -Rugosity of the
skull was considered to be a synapomorphy for Cro-
taphytus by Frost and Etheridge (1989). Although
rugosities may indeed be found in all Crotaphytus
taxa (rugosities are not found in Gambelia), there is
much variation with respect to the ontogenetic pe-
riod during which rugosities develop. For example,
most C. collaris develop rugosities as subadults, while
C. bicinctores, C. dickersonae, and C. nebrius con-
sistently develop rugosities only after reaching adult
size. In C. grismeri, C. insularis, C. reticulatus, and
C. vestigium, rugosities may be lacking even in large
adults. For example, an extremely large C. vestigium
(REE 2935; SVL = 125 mm) completely lacks skull
rugosity, while several much smaller individuals
have them. This variation was coded as a binary
character with the absence of skull rugosity as state
0, and the presence of skull rugosity at some point
in ontogeny as state 1. This character could not be
polarized.
Axvu. SKELETON
Presacral Vertebrae (Character 38).-The presa-
cral vertebrae of crotaphytids are procoelous and
have supplemental articular facets, zygosphenes and
zygantra, medial to the pre- and postzygapophyses.
A large posterodorsally oriented suprazygapophy-
sial process is present on the atlas. Crotaphytids
retain the apparently plesiomorphic mode of eight
cervical vertebrae and 24 presacral vertebrae, al-
though individuals occasionally have nine cervicals
and more frequently may have 23 or 25 total pre-
sacrals. Four to seven ventrally keeled intercentra
- -
Fig. 16.- Hyoid skeletons of (A) Crofaphy~uscollaris (REE 2952,
adult male, SVL = 131 mm), (B) C. dickersonae (REE 2905,
adult male, SVL = 106 mm), and (C) Gambelia copei (REE 2800,
adult female, SVL = 123 mm). B = body ofhyoid, Bh = Basihyal,
Cbl = first ccntobranchial, Cb2 = second ceratobranchial, Ch
= Ccratohyal, Hh = hypohyal. Scale -- 10 mm.
occur between the anteriormost cervical vertebrae
and these decrease in size posteriorly.
The zygosphenes and zygantra of all crotaphytid
taxa except Gambelia silus are weakly to moderately
developed, according to the criteria established by
Hoffstetter and Gasc (1969) and modified by de
Queiroz (1987). In the weak form, the facet of the
zygosphene faces dorsolaterally, while in the mod-
erately developed form, the facet faces either lat-
erally or ventrolaterally. The most strongly devel-
oped form of zygosphene is characterized by a ven-
trolaterally facing facet with a notch separating this
facet from the prezygapophysis. This condition is
approached in four of five G. silus, in which either
a notch is present or a very thin sheet of transparent
bone fills the space. Although notched zygosphenes
are present in several of the outgroup taxa, including
corytophanids, iguanids exclusive of Dipsosauncs,
Uranoscodon superciliosus, Polychrus marmoratus,
and some Enyalius (E. boulengeri, E. bilineatus),
the condition of G. silus is considered to be the
derived state within Crotaphytidae.
Caudal Vertebrae (Characters 39,40).-The num-
ber of caudal vertebrae present in crotaphytids is
remarkably consistent with all of the species having
between 54 and 63. No gaps were obser-ved sug-
gesting that the number of caudal vertebrae is not
phylogenetically informative within Crotaphytidae.
Most of the caudal vertebrae bear neural arches,
transverse processes, and haemal arches, all of which