1 4 University of California Publications in Zoology 



the outgroups is relatively small, which enabled me to examine representatives of all of 

 their included genera and most of their included species. Nevertheless, each one of these 

 outgroups has at some time been proposed as the closest relative of iguanines: basiliscines 

 by Etheridge (1964a); crotaphytines by Savage (1958), who actually included them within 

 iguanines, morunasaurs by Etheridge (Fig. 4), who considered them to be part of a group 

 ancestral to various iguanid lineages; and oplurines by Avery and Tanner (1971). 



Evidence about character polarity based on outgroups is not always unambiguous, 

 especially in cases such as this one in which relationships of the various outgroups to the 

 ingroup are unclear (Maddison et al., 1984; Donoghue and Cantino, 1984). I made a 

 compromise between using the maximum number of characters and using only those 

 characters whose polarities were completely unambiguous based on the outgroup evidence. 

 When all four outgroups suggested the same polarity, that polarity was accepted. When all 

 members of all four outgroup taxa did not suggest the same polarity, I considered the 

 polarity determinable only in those cases where all members of three of the four outgroups 

 suggested the same polarity. In all other cases I considered the polarity undeterminable. 

 The reasoning behind this decision is given in Appendix 11. 



BASIC TAXA 



I chose the iguanine genera recognized by Etheridge (1982) as the basic taxa among which 

 phylogenetic relationships were to be determined. Ideally, the basic taxa would all be 

 monophyletic; however, this information is currently unavailable for the iguanine genera. 

 Although it would be preferable from a theoretical viewpoint to use less inclusive taxa 

 (e.g., species) as basic taxa and then determine which genera are monophyletic, this 

 alternative has practical limitations. The characters used in this study are primarily 

 osteological, and many iguanine species are either poorly or not at all represented by 

 osteological preparations. Furthermore, variation within iguanine genera generally appears 

 to be much less than variation among them. For these reasons, using genera rather than 

 species as basic taxa probably gives a more accurate estimation of the range of variation 

 within basic taxa. Nevertheless, overall similarity should not be taken as evidence for 

 monophyly, and I attempt here not only to determine relationships among the iguanine 

 genera but also to evaluate the evidence for the monophyletic status of each. These are not 

 necessarily independent issues. 



THE PROBLEM OF VARIATION 



Character variation within basic taxa is a problem seldom addressed in the systematic 

 literature. Contrary to the impression given in many systematic studies, such variation is 

 ubiquitous, especially when the basic taxa are higher taxa that are themselves composed of 

 diverse subgroups. Nevertheless, many systematic studies apparently ignore this variation 

 or are based on such small samples that no variation within basic taxa is detected. Many of 

 the characters used in this study vary within one or more of the iguanine genera, the basic 



