58 



University of California Publications in Zoology 



B 



tc 



ita\ 



mc 



^-pre 



FIG. 29. Dorsal views of the posterior ends of the right mandibles of three Dipsosaurus dorsalis-(A) RE 

 355, (B) RE 1576, (C) RE 356-showing ontogenetic divergence of the posterior ends of the medial and 

 tympanic crests of the retroarticular process. Scale equals 1 mm. Abbreviations: ap, angular process; ar, 

 articular; mc, medial crest; pre, prearticular; rap, retroarticular process; sur, surangular; tc, tympanic crest. 



adherence to the ontogenetic criterion for assessing character polarity (Nelson and Platnick, 

 1981; Patterson, 1982) would, in this case, produce results that conflict with those of 

 outgroup comparison. Phylogeny, however, is a procession of changing ontogenies. 

 Therefore, I treat the ontogenetic development of a large angular process and the lack of 

 such development as different character states. When characters are conceived as 

 ontogenetic transformations rather than instantaneous forms (e.g., large vs. small angular 

 process), there can be no conflict between ontogeny and outgroups. Ontogenetic 

 transformations do not provide information about character phylogeny; they are the 

 characters themselves (de Queiroz, 1985). 



The retroarticular process of iguanines extends from the posterior end of the mandible. 

 It is bounded on either side by crests: the tympanic crest laterally, and medially by what I 

 will simply call the medial crest. In most iguanines, the two crests converge posteriorly, 

 and the retroarticular process is triangular (Fig. 28). This condition is also seen in juvenile 



