Phylogenetic Systematics of I guanine Lizards 1 49 



10. Large dewlap (88-B). The polarity of this character is questionable. Large 

 dewlaps occur also in Brachylophus and Iguana; within Ctenosaura they occur only in C. 

 palearis. 



Fossil record: The oldest fossils referred to Ctenosaura are from the Holocene of 

 Mexico (Langebartel, 1953; Ray, 1965; Estes, 1983). Stevens (1977) suggested that a 

 fragment of a left dentary from the early Miocene of Texas was probably close to 

 Ctenosaura. 



Comments: Bailey (1928:7) claimed that "it is impossible to distinguish between the 

 genus Ctenosaura and its near allies by means of skeletal characters." This is false. 

 Osteological synapomorphies are identifiable not only in Ctenosaura but also in all of the 

 other iguanine taxa that have traditionally been assigned the rank of genus. Even within 

 Ctenosaura, monophyletic groups can be recognized on the basis of skeletal characters. 



At least three characters suggest a close relationship among Ctenosaura, Iguana, and 

 Cyclura: extension of the surangular well anterior to the coronoid apex (39-B); tendency of 

 the pterygoid tooth row to double ontogenetic ally (49-B,-C); and absence of posterolateral 

 processes on the pleurapophyses of the second sacral vertebrae (57-B). Nevertheless, I 

 have left the relationships of Ctenosaura to other Iguanini unresolved because all three of 

 these characters are ambiguous. The first is variably present in Ctenosaura, the third is 

 variable in Cyclura, and the second is variable in both Ctenosaura and Cyclura. Thus, 

 provided that the monophyly of each of these taxa is accepted, every one of these characters 

 must involve homoplasy. If the homoplasy is interpreted as acquisition of the derived state 

 of these characters in the most recent common ancestor of Ctenosaura, Cyclura, and 

 Iguana, with subsequent reversal in certain taxa, then the close relationship among these 

 three taxa might still be advocated. At present, however, the homoplasy can just as 

 reasonably be interpreted as convergence, in which case the close relationship is not 

 supported. I prefer to leave the relationships of Ctenosaura within Iguanini unresolved 

 until additional evidence suggests that one of the alternative interpretations of homoplasy in 

 the characters that vary within basic taxa is more plausible. The relationship between 

 Ctenosaura and Cyclura is discussed further in the comments on Cyclura, below. 



The species bakeri, clarki, defensor, palearis, and quinquecarinata, here included in 

 Ctenosaura, are sometimes placed in a separate genus, Enyaliosaurus. Etheridge (1982) 

 reviewed the history of the problem as follows: 



The most recent taxonomic revision and key for the genus Ctenosaura is that of 

 Bailey (1928), but several important papers on individual species or groups of 

 species have appeared subsequentiy. Bailey recognized 13 species, including those 

 forms with a relatively small body size and a short, strongly spinose tail referred by 

 some authors to Enyaliosaurus. Following Gray's (1845) description of 

 Enyaliosaurus the name was seldom used until its revival by Smith and Taylor 

 (1950: 75). In this work the species clarki, defensor, erythromelas, palearis and 



