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1996 McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 9
debate concerning crotaphytids has been whether or
not Garnbelia should be synonymized with Crota-
phytus (Smith, 1946; Robison and Tanner, 1962;
Weiner and Smith, 1965; Montanucci, 1969, 1978;
Montanucci et al., 1975; Tanner and Banta, 1977).
Nevertheless, very little character evidence has been
presented supporting the monophyly of Crotaphy-
tidae. Etheridge and de Queiroz (1988) recognized
crotaphytids as a monophyletic group on the basis
of a unique combination of derived, yet highly ho-
moplastic features: the presence of posterior cora-
coid fenestrae and female gravid coloration, and the
absence of postfrontal bones and a middorsal scale
row. Frost and Etheridge (1 989) considered crota-
phytids to be monophyletic on the basis of three
reversals: presence of palatine teeth, posterior cor-
acoid fenestrae, and ribs on the third cervical ver-
tebra (the last ofwhich is only infrequently observed
in crotaphytids). In each of these analyses, character
support for Crotaphytidae was dependent upon its
placement within the ingroup topology. The follow-
ing is a list of synapomorphies of Crotaphytidae
recognized in this study: presence of black oral pig-
mentation (reversed within Crotaphytus), presence
of a posterolaterally projecting jugal-ectopterygoid
tubercle immediately posterior to the maxillary tooth
row, presence of posterior coracoid fenestrae, the
tympanic crest of the retroarticular process of the
mandible curves posterodorsally, the parietal and
frontal strongly overlap the medial process of the
postorbital, the supratemporal lies in a groove along
the ventral or ventrolateral border of the supratem-
poral process of the parietal (reversed in most G.
silus or convergent in Crotaphytus and other Garn-
belia), presence of palatine teeth, and contact of the
prefrontal and jugal in the anterolateral border of
the orbit.
The terminal taxa utilized in this study include
the currently recognized species of Crotaphyrus (C.
antiquus, C. bicinctores, C. collaris, C. dickersonae,
C. grismeri, C. insularis, C. reticulatus, and C. ves-
tigium) and Garnbelia (G. coronat, G. silus, and G.
wislizenii). Over the course of this study, it was de-
termined that at least one and probably two addi-
tional species should be recognized. These include
two taxa currently recognized as subspecies, C. c.
nebrius and G. bv. copei (see taxonomic accounts for
data supporting the elevation of these taxa to full
species). These species were also included in the
analysis.
Another population of Gambelia that may even-
tually prove to be a full species is the population of
G. ivislizenii on Isla Tiburon in the Gulf of Califor-
nia. The four osteological specimens examined in
this study lacked autotomic fracture planes in the
caudal vertebrae. Fracture planes are present in all
other G. \clislizenii (n = 19) and G. silus (n = 5)
specimens examined, although they appeared to be
fused in three of ten G. copei. Unfortunately, no
osteological specimens were available from adjacent
Sonora and it could not be determined ifthe absence
of fracture planes is confined to this insular popu-
lation. If this population proves to be a separate
species, it may be the only endemic reptile or am-
phibian on Isla Tiburon, a land-bridge island that
supports an extensive herpetofauna.
The remaining subspecies of Crotaphytus collaris
and Gambelia nislizenii were not treated as separate
terminal taxa because no evidence has been pre-
sented, nor has any been discovered over the course
of this investigation, suggesting that these forms are
discrete evolutionary entities. Rather, they are pat-
tern or convenience classes (Frost et al., 1992), color
morphs largely consistent over an extensive area,
but grading smoothly into other color morphs at
their boundaries.
Etheridge and de Queiroz (1988) and Frost and
Etheridge (1 989) provided evidence for the mono-
phyly of nine suprageneric groups (elevated to fam-
ilies in the latter study) within Iguania. Interfamilial
resolution was elusive and their strict consensus tree
(at the familial level) was an unresolved polytomy.
However, they were able to substantially reduce the
number of equally parsimonious interfamilial to-
pologies as depicted in their 12 unrooted trees with
rooting points (Fig. I). Thus, despite the continuing
lack of unambiguous interfamilial resolution, the
outgroup situation has improved considerably. In
this analysis, characters were considered to be po-
larized only when the polarity assessment was con-
sistent with all 12 unrooted trees.
For each of the eight remaining iguanian families,
exemplars were examined for the purpose of char-
acter polarization. The choice of exemplars was
based whenever possible on the results of recent
intrafamilial phylogenetic analyses. Thus, basal lin-
eages have been proposed for clades within the fam-
ilies Phrynosomatidae (Presch, 1969; Montanucci,
1987; Etheridge and de Queiroz, 1 988; de Queiroz,
1989, 1992; Wiens, 1993a, 1993b), Tropiduridae