156 University of California Publications in Zoology 



Node 7 (unnamed) 



1. Dorsal crest scales low-keeled to flat; inconspicuous throughout length of crest (13- 



1). 



2. Tail strongly spinose throughout its length, and about same length as body (snout- 

 vent/tail length = 0.48-0.56); fewer than 30 caudal vertebrae (17-1). 



In some: middorsal scale row broadly discontinuous in lumbosacral region (14-1), 

 This character occurs also in C. hemilopha. 



Ctenosaura clarki 

 1. Prefrontal contacts jugal behind lacrimal foramen (4-B). This character occurs also 

 in some C. quinquecarinata, in which it is interpreted as convergent. 



Ctenosaura defensor 



1. Mode of five premaxillary teeth (3-1). 



2. Frontal portion of crista cranii projects anteriorly to form a step from frontal to 

 prefrontal bones (5-1). 



3. Crowns of posterior marginal teeth with a maximum of five or more cusps (8-B). 



4. External signs of parietal eye inconspicuous or absent (11-1). 



5. Scales on anterodorsal surface of thigh enlarged and spinous (15-2). 



6. Anterior keels of subdigital scales at base of pedal digit III enlarged and fused at 

 their bases to form a comb (16-1). 



7. Proximal rows of smaller scales between whorls of enlarged, spinous caudal scales 

 small or absent (18-3). 



The results of the present analysis indicate that Enyaliosaurus (including bakeri, 

 palearis, quinquecarinata, clarki, and defensor) is a monophyletic group, but that 

 Ctenosaura in the narrow sense (acanthura, pectinata, similis, and hemilopha) is not. 

 Ctenosaura hemilopha appears to have shared a more recent common ancestor with 

 Enyaliosaurus than with the other Ctenosaura (in the narrow sense). However, the 

 character that suggests an exclusive common ancestry for hemilopha and Enyaliosaurus, a 

 reduction in the number of intercalary scale rows between the whorls of enlarged, spinous 

 caudal scales, is problematical, in that it does not occur in all bakeri. Nevertheless, if 

 bakeri and palearis are sister taxa, it is simpler to interpret the incongruence as a reversal in 

 some bakeri rather than four separate acquisitions of the derived condition (1-in hemilopha, 

 2-in some bakeri, 3-in palearis, 4-in the common ancestor of quinquecarinata, clarki, and 

 defensor). In any case, the monophyly of Ctenosaura in the narrow sense is doubtful even 

 if this character is rejected, for there are no derived characters found in acanthura, pectinata, 

 similis, and hemilopha that are not also found in the other taxa. Rather than the two being 

 separate taxa, Enyaliosaurus appears to be a subgroup of a more inclusive Ctenosaura. 



There currentiy exist several problems concerning species-level taxa within Ctenosaura. 

 Smith and Taylor (1950) considered the specimens from the west coast of Mexico assigned 

 to C. acanthura by Bailey (1928) to be C. pectinata. Based on a conflict between the 



