8 University of California Publications in Zoology 



The currently recognized iguanine group is based on the work of Etheridge. In his 

 paper on the systematic relationships of sceloporine lizards, Etheridge (1964a) showed that 

 the two primary characters used by Savage (1958) to diagnose the iguanines were actually 

 more widespread within the Iguanidae, and were thus insufficient to diagnose the group. 

 He listed four fundamental differences between Crotaphytus and Savage's other iguanines, 

 and asserted that if Crotaphytus was considered to be an iguanine, no character or 

 combination of characters could be used to diagnose that group. Once he removed 

 Crotaphytus from the group, the iguanines were readily diagnosed by their unique caudal 

 vertebrae. Except for his recognition of Enyaliosaurus as a genus separate from 

 Ctenosaura, Etheridge's (1964a) concept of the iguanines is identical to that held today 

 (Etheridge, 1982). 



Despite the long history of iguanines as a recognized group and the great interest in 

 many aspects of iguanine biology (e.g., Burghardt and Rand, 1982; Troyer, 1983), the 

 interrelationships among the iguanine genera and the relationships of iguanines to other 

 iguanians remain largely unknown. Commonly held beliefs are that Ctenosaura and 

 Cyclura are closely related (Barbour and Noble, 1916; Bailey, 1928; Schwartz and Carey, 

 1977), and that the same is true of the Galapagos iguanas Amblyrhynchus and Conolophus 

 (Heller, 1903; Eibl-Eibesfeldt, 1961; Thornton, 1971; Higgins, 1978). As mentioned 

 above, Mittleman (1942) and H. M. Smith (1946) have offered dendrograms depicting 

 their views on the relationships of the North American iguanines. 



Recent studies have examined diverse data for clues about the interrelationships among 

 the iguanine genera, but have met with limited success. Zug (1971) studied the arterial 

 system of iguanids. He published shortest-connection networks for more than 40 iguanid 

 genera, some based on his arterial characters and others based on characters obtained from 

 the literature, most of which were osteological. Other shortest-connection networks 

 constructed from data on arterial variation within various suprageneric assemblages of 

 iguanids, including iguanines, were also presented. Nevertheless, Zug doubted the 

 usefulness of his arterial characters in iguanid systematics, stating: "The arterial characters 

 employed herein appear to be of minimal value in iguanid classification. At the intrafamilial 

 level, they are disruptive and form groups of questionable zoogeographic unity" (Zug, 

 1971:21). 



There has been but a single study in which the relationships among all known iguanine 

 genera were sought, that of Avery and Tanner (1971). These authors provided 

 descriptions of the iguanine skeleton, head and neck musculature, tongue, and hemipenes, 

 and gave a number of osteological measurements. They based their hypothesis of 

 relationships on mean length-width ratios of bones, assuming that "a difference of forty or 

 less points between means of the same bone indicates a close relationship" (Avery and 

 Tanner, 1971:67). Large numbers of such similarities were taken to indicate close 

 phylogenetic relationship among taxa and were used in some unspecified way to construct a 

 phylogenetic diagram (Fig. 3). Avery and Tanner examined small series (never more than 

 five individuals of a single species), giving no consideration to allometric changes in the 

 ratios that they used. I suspect that many of these ratios are correlated with a single 



