McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS Fig. 22.-Ventral view of Gambelia ~c~islizenii (TNHC 33200) showing the femoral pore series extending beyond the angle of the knee. Fig. 23.-Ventral view of Crotaphytw reticulafur (TNHC 28364) showing the jet black femoral pores present in males. AGF = antegular fold, GF = gular fold.
BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY AGF Fig. 24.-Ventral view of the neck folds of Ctoraphyrus reticrtlarus (EL 3250). Fold terminology follows Frost (1992). AGF = an- tegular fold. GF - gular fold. PostanalScales. -In some iguanian lizards, males can be differentiated from females by the presence of enlarged postanal scales. Within Crotaphytidae, the postanal scales are enlarged in all male Gam- belia, as well as C. grismeri, Crotaphytus nebrius, and most C. bicinctores and C. collaris. The con- dition of the postanal scales is more variable in C. vestigiurn and C. insularis, with roughly equal pro- portions of males having large or only slightly en- larged scales. The postanal scales are not enlarged or are only slightly enlarged in C. antiquus, C. re- ticulatus, and C. dickersonae, although they may be larger than in females. Attempts to code this char- acter were prohibited by continuous variation in the size of the postanal scales in C. bicinctores. C. col- laris. C. dickersonae, C. insularis. C. reticulatus, and C. vestigium. Furthermore, this character could not be polarized as enlarged postanal scales are present in phrynosomatids, oplurids, many anoles (Cha- NO. 32 maeleolis chamaeleonides, Phenacosaurus, and most Anolis), and some Leiocephalus (although Pregill [1992] found that enlarged postanal scales were de- rived within the genus). TailSkin (Character 54).-In all crotaphytids, the skin of the tail is relatively weakly adherent to the underlying musculature such that the skin can be removed easily. This condition contrasts strongly with that observed in most iguanians with fracture planes, such as Dipsosaurus, Sceloporus, and Oplu- rus, in which the skin is bound to the underlying musculature by connective tissue and is nearly im- possible to remove in one piece. This condition is more strongly developed in Crotaphytus than in Gambelia, such that in the former, the skin of the posterior 40-50 mm ofthe tail easily slips OK Loosely adherent skin that is easily removed from the ter- minal portion of the tail appears to be unusual if not unique among iguanians and is therefore con- sidered to be the derived state (1) in this analysis. Crotaphytids, like many fine-scaled iguanian liz- ards, have extensive lateral neck and gular folding. Both Crotaphytus and Gambelia share a standard complement of folds that includes gular, antegular, antehumeral, postauricular, longitudinal neck, and supra-auricular folds (terminology follows Frost, 1992). None of these folds are unique to Crotaphy- tidae and most are similar to folds present in a wide range of iguanian lizards. For example, the gular fold is well developed, enclosing a region of reduced squamation, and is continuous with the antehu- meral fold. Also, the antegular fold is continuous with the oblique neck fold. However, phylogeneti- cally informative variation does occur in the folds. As is the case with most fine-scaled species, addi- tional folds are ofien present with varying degrees of consistency. Thus, I have referred to the above- mentioned complement of folds as the standard pat- tern and will restrict the discussion to this series. Gttlar Fold (Character 55; Fig. 24-27). -The gular fold of Crotaphytus differs from that of Gambelia in that there is a pair of skin folds that separate from the gular fold and project posteromedially. These folds, which may be ventromedial continuations of the antehumeral folds (R. Etheridge, personal com- munication, 1993) usually meet midventrally and form a single longitudinally oriented midventral fold that extends posteriorly for a short distance. In the triangular-shaped region between the folds, the scales are reduced in size. In Gantbelia, a pair of similar
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