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McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 37<br />
Fig. 25.-Ventral view of the neck folds of Garnbelia wislizenii<br />
(SDSNH 68663). Fold terminology follows Frost (1992). AGF<br />
= antegular fold, GF = gular fold.<br />
folds may occur; however, they are shorter and appear<br />
near the lateral borders of the gular fold. As a<br />
result, the area of reduced squamation seen in Gambelia<br />
takes the form of a uniform band that extends<br />
across the width of the gular fold. Those outgroup<br />
taxa with gular folds examined here display both<br />
conditions of the fold with phrynosomatids, the<br />
oplurid Chalaradon madagascariensis, chamaeleonids<br />
(except Hydrosaurus pusfulatus), the corytophanids<br />
Basiliscus vittatus and Laemanctus, the<br />
hoplocercid Enyalioides lariceps (four of five), and<br />
polychrotids displaying the Gambelia form, and the<br />
hoplocercids Enyalioides praestabilis and E. oshaugnessyi,<br />
the corytophanid Basiliscur plumifons,<br />
the oplurid genus Oplum (0. firinensis and 0.<br />
saxicolus variable), and the iguanid Dipsosaurus<br />
displaying the Crotaphytus form. Most tropidurids<br />
have incomplete gular folds or lack them altogether;<br />
thus, the evaluation of this character for Tropiduridae<br />
is difficult. Uranoscodon superciliosus, which<br />
has a complete gular fold, displays the Gambelia<br />
form. The only other species within Tropidurini with<br />
Longltudlnal neck<br />
Postauricular I Supra-auricular<br />
Oblique neck<br />
--"<br />
Fig. 26.- Lateral view of the neck folds of Cro~aphy~usre~iculatur<br />
(EL 3250). Fold terminology follows Frost (1992).<br />
complete gular folds are Tropidurus azureum. T.<br />
flaviceps, and T. plica (Frost, 1992), species far re-<br />
moved from the basal lineages of the clade, and,<br />
thus, unable to shed light on this polarity decision.<br />
Because ofambiguity in the outgroup taxa, this char-<br />
acter was left unpolarized.<br />
Supra-auricular Fold (Character 56; Fig. 26,27). -<br />
Frost (1992) defined the supra-auricular fold as a<br />
continuation of the dorsolateral fold that passes<br />
above the tympanum. In crotaphytids, a similar fold<br />
is present; however, it originates from the postaur-<br />
icular fold at a point roughly midway between the<br />
dorsal and ventral borders of the external auditory<br />
meatus. Without strong evidence to the contrary, I<br />
treat the crotaphytid fold as homologous with that<br />
described by Frost (1992) and therefore apply his<br />
standardized nomenclature. The condition of the<br />
supra-auricular fold, in which it originates midway<br />
between dorsal and ventral borders of the external<br />
auditory meatus, is present in many iguanian taxa<br />
Fig. 27.-Lateral view of the neck folds of Gambelia wis1i:enii<br />
(SDSNH 68663). Fold terminology follows Frost (1 992).