COMPARISONS WITH PREVIOUS HYPOTHESES 



Although a close relationship among some or all of the taxa currently placed in Iguaninae 

 was recognized by several nineteenth-century authors, no explicit hypotheses about 

 phylogenetic relationships among the various iguanine genera appeared until the twentieth 

 century. The phylogenetic relationships proposed here are both similar in some respects 

 and different in others when compared with previous hypotheses about iguanine 

 relationships. In this section, I evaluate these previous hypotheses in light of the results of 

 the present study. 



Barbour and Noble (1916) and Bailey (1928) both hypothesized a close relationship 

 between Cyclura and Ctenosaura, and Schwartz and Carey (1977) further proposed that 

 Cyclura originated from Ctenosaura. Neither of these hypotheses is supported by the 

 results of the present study. First, Ctenosaura possesses at least three characters that are 

 derived relative to the condition seen in Cyclura (premaxillary process of maxilla curves 

 dorsally; short posterolateral processes of parabasisphenoid; elongate subocular scale), and 

 thus cannot be considered ancestral to the latter. Second, Cyclura shares more derived 

 characters with Iguana than it does with Ctenosaura, implying that Cyclura shared a more 

 recent common ancestor with Iguana than with Ctenosaura. The relationships among these 

 three taxa are discussed further in the comments on Cyclura in the Diagnoses section, 

 below. 



Mittleman (1942) proposed a phylogenetic scheme for the North American iguanids, 

 including Ctenosaura, Dipsosaurus, and Sauro ma I us (Fig. 1). This phylogeny was 

 modified slighdy by H. M. Smith (1946), who removed Ctenosaura from a position of 

 direct ancestry to all other North American iguanids and placed Dipsosaurus and 

 Sauromalus close to a group composed of what are now considered the sceloporines and 

 crotaphytines rather than to just part of this radiation (compare Figs. 1 and 2). Although 

 Smith did not include iguanines other than those occurring within or very near to the United 

 States in his branching diagram, it is clear from his comments on the "herbivore section" 

 (group II in Fig. 2) that he also considered Iguana, Amblyrhynchus, Conolophus, and 

 Cyclura to be part of this group. 



Common to the Mittleman (1942) and Smith (1946) phylogenies is the notion that 

 iguanines are ancestral to the other North American iguanids-that is, that some iguanines 

 shared a more recent common ancestor with these other iguanids than they did with other 

 iguanines. This idea seems to be related to another notion held by both Mittleman and 

 Smith, namely that iguanines are "primitive" iguanids. According to Mittleman 

 (1942:1 12), "Dipsosaurus is probably the most primitive of the North American Iguanidae 



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