IGUANINE MONOPHYLY 



The family Iguanidae is a heterogeneous assemblage of iguanian lizards distinguished from 

 other iguanians (agamids and chamaeleontids) primarily by their possession of pleurodont 

 rather than acrodont teeth (e.g., Boulenger, 1884; Cope, 1900; Camp, 1923). Pleurodonty 

 occurs in nearly all other squamates (except trogonophid amphisbaenians) and in most 

 other lepidosauromorphs (except sphenodontidan rhynchocephalians), although the teeth of 

 early lepidosauromorphs are unlike those of most squamates in that they are set in shallow 

 depressions (Gauthier et al., 1988). Thus, the primary diagnostic feature of Iguanidae is 

 probably plesiomorphic for Iguania and is not, therefore, evidence for the monophyletic 

 status of the family. Other characters given in a recent diagnosis of Iguanidae (Moody, 

 1980) all either appear to be plesiomorphic for Iguania or do not characterize all iguanids 

 (Estes et al., 1988). There is presently no evidence that Iguanidae is monophyletic. 

 Renous (1979) and Moody (1982) have even suggested that some iguanids may be more 

 closely related to some or all of the acrodont iguanians than they are to other iguanids. 



Because Iguanidae is unlikely to be monophyletic, it seems advisable to break this 

 family into groups for which there is evidence of monophyly. A number of presumably 

 monophyletic groups of iguanids have been proposed and given informal names (Savage, 

 1958; Etheridge, 1964a, 1976 in Paull et al.; Estes and Price, 1973; Etheridge and de 

 Queiroz, 1988); however, it is beyond the scope of this paper to revise the taxonomy of all 

 pleurodont iguanians. Furthermore, the relationships of these informal groups to agamids 

 and chamaeleontids are unclear (Estes et al., 1988). Therefore, I provisionally retain the 

 taxon Iguanidae, emphasizing that it may be paraphyletic and thus may have to be 

 abandoned at some future time. 



I present evidence below for the monophyletic status of iguanine iguanids. Because I 

 feel that it would be premature to disband Iguanidae, but because I also feel that the 

 monophyletic groups of iguanians should be recognized, I resurrect the taxon Iguaninae. 



Traditionally, recognition of a taxon within a larger one is accompanied by the 

 assignment of all members of the larger taxon to a taxon at the same categorical level as the 

 new one. This often leads to the recognition of some new paraphyletic group, especially in 

 cases such as this one where the author has adequate knowledge of only part of the larger 

 group being subdivided. Because paraphyletic taxa are undesirable in a phylogenetic 

 taxonomy, I chose a logical alternative: to leave the remaining iguanids unassigned to taxa 

 of rank equal to that of Iguaninae. Indeed, following Gauthier et al. (1988), I have more or 

 less abandoned the use of categorical ranks. My use of "genera" as basic taxa is the result 

 of historical inertia, and I do not mean to imply that they are equivalent in any biologically 



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