Phylo genetic Systematics of I guanine Lizards 99 



of enlarged, spinous scales is variable along the tail, generally decreasing posteriorly. The 

 maximum number of rows between whorls of enlarged scales ranges from none in some 

 Ctenosaura defensor (Bailey, 1928; Duellman, 1965) to about six in Cycliira nubila 

 (Schwartz and Carey, 1977). Within Ctenosaura, there appears to be a negative correlation 

 between the size of the scales in the enlarged whorls and both the number of scale rows 

 between them and the relative length of the tail. 



The evolution (or loss) of spinose tails appears to have occurred repeatedly within 

 iguanids. Like most iguanines, basiliscines, crotaphytines, Chalarodon, and some 

 Enyalioides have more or less uniform caudal squamation without spinous scales. Other 

 Enyalioides, Morunasaurus, Hoplocercus, and Oplurus have whorls of enlarged spinous 

 scales separated by smaller scales. The short, spinose tail of Hoplocercus is as extreme as 

 anything seen in Ctenosaura. Although it seems likely that tails with whorls of enlarged, 

 spinous scales are apomorphic within iguanines, this polarity is equivocal unless 

 assumptions are made about either the relationships among outgroups and ingroup or those 

 within morunasaurs and oplurines. 



Cross-sectional Body Shape. Sauromalus differs from all other iguanines in its cross 

 sectional body shape. All other iguanines are either laterally compressed or cylindrical in 

 cross section, while Sauromalus is strongly depressed. The shape of the body of 

 Sauromalus and several other of its distinctive skeletal features (e.g., low neural spines, 

 horizontal orientation of the suprascapular short and broad pelvic girdle) are probably 

 redundant characters. They are treated separately here because (1) the correlation among 

 them is only hypothesized, and (2) some of them are known to change without 

 accompanying changes in the others (e.g., not all depressed lizards have suprascapulae that 

 form sharp angles with the scapulae). 



Cross-sectional body shape in members of the four outgroups examined in this study 

 varies in such a way that it is impossible to determine the plesiomorphic shape for 

 iguanines. Basiliscines are laterally compressed. Some morunasaurs are compressed 

 {Enyalioides) while others are depressed {Hoplocercus), and both crotaphytines and 

 oplurines are depressed, though generally not as strongly as Sauromalus. 



