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McGU IRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 3 1
anterior border of the scapular fenestra is tentatively
coded as the derived condition.
Clavicles (Character 45). - In Garnbelia, the clavicles
usually (all Gambelia except two of 23 G. wislizenii)
bear extensive fenestrations. Fenestrations
were also present in all Crotaphytus reticulatus examined,
although Montanucci (I 969) found that they
were absent in six of the 14 specimens he examined.
These fenestrations were absent in all 39 C. collaris
examined, as well as in the 14 C. rtebrius and five
C. insularis examined. However, in the remaining
species of Crotaphytus, there was much variability
in this character with four of 2 1 C. bicinctores, two
of four C. antiquus, five of 16 C. dickersonae, three
of five C. grismeri, and two of 2 1 C. vestigiu~n having
fenestrated clavicles. Although Weiner and Smith
(1 965) noted that clavicular fenestrations were absent
in the 54 specimens of C. collaris they examined,
Robison and Tanner (1 962) observed them in
20 percent of their specimens (although they included
specimens of the yet-to-be-described C. bicinctores
in their sample, which at the time was
considered to be C. c. bailey~] and Montanucci ( 1 969)
observed them in one of 45 specimens collected
from Kansas and Oklahoma. Thus, clavicular fenestrations,
although uncommon, are occasionally
present in C. collaris and it seems likely that additional
specimens will reveal their presence in C.
nebrius and C. insularis as well. Clavicular fenestrations
are rare in the basal lineages of the outgroup
taxa, being found only in Basiliscus, Laemanctus.
some Corytophanes hernandezi (REE 1 800, SDSNH
68090, although considered absent from this species
by Lang, 1989), some Uma inornata, Ctenoblepharys
aa3persus. some Leiolepis belliana, Phjsignathus
concincinus, some P. lesueurii, and Enyalius
brasiliensis. Therefore, the presence of clavicular
fenestrations is considered to be the derived state.
Interclavicle. -The interclavicle is an unpaired
median element that lies along the ventral margin
of the pectoral girdle. It varies extensively in form,
although it usually is in the shape of an anchor or
arrow. Lateral processes, present anteriorly, are in
close contact with the proximal ends ofthe clavicles,
while a long, narrow posterior process is bordered
laterally by the epicoracoid cartilages and the sternum.
In most Crotaphyrus and some Gambelia, the
interclavicle expands laterally becoming diamondshaped
just anterior to the sternum. Although Weiner
and Smith (1965) considered this character to
be phylogenetically informative, there is continuous
variation in this feature and it was not included in
the phylogenetic analysis.
Slmrnur?~ and Xiphisterna. -The sternum is a median,
diamond-shaped element composed entirely
of calcified cartilage. Anterolaterally, the sternum
thickens, forming grooves into which fit the epicoracoid
cartilages. These tongue-in-groove joints allow
for extensive mobility of the pectoral girdle elements
during locomotion (Jenkins and Goslow,
1983). The sternum also articulates medially with
the posterior process of the interclavicle. In the center
of the sternum there may be a fontanelle that,
when present, is usually invaded by the interclavicle.
Posterolaterally, the sternum bears four or five facets
that serve as attachment points for the sternal
and xiphisternal ribs and the postxiphisternal rods.
The posteriormost facets (those that give rise to the
xiphisternal ribs) are separated slightly more widely
in eastern Crotaphytus collaris than in other crotaphytids.
A similar, albeit more extreme, condition
is observed in Sauromalus (de Queiroz, 1987). This
may be related to the more depressed habitus of
eastern C. collaris and their greater propensity for
crevice dwelling. This condition was not coded as
a character. Weiner and Smith (1 965) noted that the
sternum of Crotaphytus is broader and shorter than
in Gar?lbelia. Although there does appear to be a
trend in this direction, this character appears to vary
continuously and was not included in the phylogenetic
portion of this analysis. No phylogenetically
informative variation was discovered in the sternum
(but see above section titled "Ribs" for discussion
of xiphisternal rib variation).
illium and Pubis (Character 46).-In Gambelia,
the iliac blades are robust and roughly cylindrical
at their distal termini, while in Crotaphytus, they
are usually laterally compressed. However, in some
C. collaris (primarily those formerly referred to C.
c. collaris), they may approach the cylindrical con-
dition observed in Garnbelia. The outgroup taxa are
extremely variable with respect to this character and
it could not be polarized.
Weiner and Smith (1965) discuss ventrolateral
curvature of the pubes and the angle at which the
two halves of the pelvic girdle meet. There does not
appear to be consistent interspecific variation in ei-
ther of these features (in fact, 1 am unaware of any
ventrolateral curvature of the pubes, although they