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University of California Publications in Zoology 



FIG. 27. Medial views of the left mandibles of (A) Iguana delicatissima (MCZ 16157) and (B) 

 Conolophus subcristatus (MVZ 77314), showing differences in the exposure of the surangular (shaded) 

 below the coronoid (cor). Scale equals 1 cm. 



fasciatus, Cyclura nubila, and Sauromalus varius does this condition appear to be more 

 than a rare variant. 



Except for Corytophanes and Oplurus quadrimaculatus, all outgroups examined have a 

 relatively large, dome-shaped portion of the surangular visible lingually between the ventral 

 feet of the coronoid. In Corytophanes, however, lingual restriction of the surangular 

 results from ventral extension of the coronoid rather than dorsal extension of the 

 prearticular, the condition in iguanines. For this reason, as well as the hypothesis that 

 Basiliscus rather than Corytophanes is the sister group of the other two basiliscine genera 

 (Etheridge and de Queiroz, 1988), I considered the superficially similar conditions seen in 

 Corytophanes and in some iguanines to be nonhomologous. Thus, the large lingual 

 exposure of the surangular between coronoid and prearticular is interpreted as 

 plesiomorphic. 



Prearticular (Figs. 6B,C, 28, 29). This bone forms the ventromedial portion of the 

 posterior end of the mandible. The prearticular bears two processes for the insertion of jaw 

 adductor and abductor muscles, the posteriorly directed retroarticular process and the 

 medially directed angular process. The retroarticular process is large in all iguanines, but 

 the relative size of the angular process is variable. In all iguanines except Amblyrhynchus, 

 the angular process is small at hatching and increases in relative size as the animal grows 

 (Fig. 28A-C). The angular process of Amblyrhynchus is very small in juveniles and 

 increases in relative size only slightly during postembryonic ontogeny (Fig. 28D-F); even 

 in large adults it has only about the same relative size as those of young of other iguanine 

 genera. 



Except for Corytophanes and Laemanctus, all outgroup taxa examined (including those 

 that are small as adults) have relatively large angular processes. Thus, if basiliscines are 

 the sister group of iguanines, then the polarity of this character is equivocal; if not, then the 

 development of a large angular process during ontogeny must be considered to be 

 plesiomorphic. Because Amblyrhynchus exhibits the nontransforming ontogeny, strict 



