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BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32
as broad as the process itself. Furthermore, the tym-
panic crest angles posterodorsally and, thus, does
not form the lateral border of the retroarticular pro-
cess as it does in most other iguanian taxa examined
(illustrations of the ancestral condition of the tym-
panic crest can be seen for Dipsosaurus dorsalis in
de Queiroz, 1987:fig. 29; for Basiliscus virtarus and
Corytophanes cristarus in Lang, 1989:fig. 3 1; and for
Physignathus cocincinus in Moody, 1 980:fig. 1 6).
The angle of the tympanic crest gives the retroar-
ticular process a twisted appearance. The orienta-
tion of the tympanic crest appears to undergo an
ontogenetic change from the standard position along
the lateral border of the retroarticular process in
juveniles to a more posterodorsal orientation in
adults. The medial crest of the retroarticular pro-
cess, discussed by de Queiroz (1987), is only vari-
ably present in crotaphytids. A similar posterodor-
sal curvature of the tympanic crest was observed
only in Oplurus cuvieri and one Polychrus acutiros-
Iris (REE 568). Therefore, this condition is inter-
preted as a synapomorphy for Crotaphytidae.
MI~CELLANEOUS FEATURES OF THE
HEAD SKELETON
Marginal Teeth (Characters 30, 31; Fig. 8, 1 l-
14).-The marginal teeth of crotaphytids are characteristic
of most pleurodont iguanians in that the
anterior teeth are conical and the posterior maxillary
and dentary teeth are compressed and tricuspid. The
dentition of crotaphytids has been described as heterodont
or weakly subheterodont (Marx, 1950; Weiner
and Smith, 1965) because the teeth sometimes
grade from conical to bicuspid then tricuspid (the
bicuspid state is often omitted). This transition usually
begins further anteriorly in Croraphyrus (mean
maxillary tooth position X = 8.1 1, n = 152) and
Gambelia silus (X = 8.08, n = 30) than in G. wislizenii
(.T = 11.27, n = 43) or G. copei (2 = 11.13,
n = 8), although the ranges overlap extensively. Heterodonty
was considered to be more developed in
Gambelia than Crotaphytus by Marx (1950) and
Weiner and Smith (1965) and was used as a character
to distinguish between the genera. However,
Montanucci (1969) found that the degree of heterodonty
was indistinguishable between adult G. ~oislizenii
and many C. collaris, especially juveniles.
The degree of cuspation is certainly more pronounced
in Gambelia than Crotaphytus and, despite
the ontogenetic variation discussed by Montanucci
(1 969), this subtle variation could probably be cod-
ed into discrete character states. However, degree
of cuspation varies continuously within iguanians
and this character therefore may be added to the
long list of currently unpolarizable differences be-
tween Croraphyrus and Gambelia. As in many ig-
uanian lizards, the number of maxillary and dentary
teeth increases ontogenetically, at least early in on-
togeny. The number of premaxillary teeth does not
increase ontokenetically.
In some individuals of both Croraphyrus (Ether-
idge, 1960; personal observation) and Gatnbelia, the
tooth rows of the mandibles and/or maxillae may
be doubled for a short distance (two sets of teeth
occumng side by side). Although Etheridge ( 1960)
hypothesized that this variation may be restricted
to males, it actually occurs in both sexes.
The number of maxillary and dentary teeth tends
to be greatest in Gambelia ~vislizenii, G. copei, and
Crotaphyrus dickersonae (Tables 3, 4). The large
number of teeth in these Gambelia is not surprising
given the elongate snout that is characteristic of these
species. The large number of teeth observed in C.
dickersonae is the result of very closely spaced den-
tition. The small number of teeth present in G. silus
is probably correlated with the truncated snout of
this species and may therefore be a plesiomorphic
retention. Discrete character states could not be as-
signed describing numbers of maxillary and dentary
teeth. Therefore, this variation was not considered
in the phylogenetic analysis.
The number of premaxillary teeth varies within
Crotaphytidae (Tables 3,4). Gambelia is character-
ized by the strong statistical mode of seven pre-
maxillary teeth, while most Croraphyrus taxa have
a somewhat weaker statistical mode of six. How-
ever, C. dickersonae and some populations of C.
collaris (those formerly referred to the subspecies C.
c. baileyi) have modes of seven. This variation was
coded as a multistate character using a step matrix
and the Manhattan distance frequency approach (see
Appendix 4). This character was not polarized.
All crotaphytids have recurved anterior maxillary
and dentary teeth, a condition that is more devel-
oped in Garnbelia than Crotaphytus, which have
broader, more peg-like teeth (especially evident in
C. rericularus). Long, slender, recurved maxillary
and dentary teeth, as present in Gambelia, were not
observed in any of the outgroup taxa and are there-
fore treated as the derived state.
Palatal Teeth (Characters 32, 33; Fig. I ]).-At
the base of the pterygoid process of each palatine,