152 University of California Publications in Zoology 



strongly spinose throughout its length and almost the same length as the body (snout- vent 

 length/total length = 0.48-0.56), fewer than 30 caudal vertebrae. 



18. Anterior (referring to first 10) whorls of strongly spinous caudal scales: (0) 

 always separated by at least two rows of intercalary scales; (1) at least some separated by 

 only one intercalary scale row, others by two or more; (2) none (or only the first) separated 

 by two intercalary scale rows, but all separated by at least one; (3) intercalary scales of 

 proximal whorls greatly reduced or absent. 



19. Snout region: (0) not inflated, sloping gradually downward; (1) inflated 

 anteriorly, sloping abruptly downward. 



Height of the vertebral neural spines may also be a useful character, but I have chosen 

 not to use it because I have no postcranial skeletons of C. defensor and C. palearis. 



The distributions of these character states among basic taxa within Ctenosaura (sensu 

 lato) and three near (Amblyrhynchina, Iguanina, Sauromalus) and two more distant 

 (Dipsosaurus, Brachylophus) outgroups are given in Table 10. Ctenosaura bakeri from 

 Isla de Utila and those from Isla de Roatan are scored separately because they differ in at 

 least three of the characters used in this analysis. Only those from Utila, the type locality, 

 are included in the analysis of relationships. 



The phylogenetic relationships suggested by the characters in Table 10 (except character 

 19, the derived state of which occurs only in the Roatan population of C. bakeri) are 

 diagrammed in Figure 55. Synapomorphies for the subterminal nodes and the basic taxa 

 are given below. Characters whose polarities were initially undeterminable were placed on 

 the cladogram after it was constructed using only those characters whose polarities were 

 determinable using other iguanines as outgroups. Ignoring the Roatan ctenosaurs and 

 intraspecific variation, these relationships require a total of 25 character transformations, 

 three more than the minimum number required by the characters themselves (C-index = 

 0.88). C-indices for the individual characters are given in Table 10. 



Node 1: Ctenosaura Wi^gmdiXm 1828 

 See above. The characters of the hypothetical ancestral Ctenosaura can be 

 reconstructed by taking the first state of each of the 19 characters in the character list. 



1). 



Node 2 (unnamed) 

 1. Parietal roof extends posteriorly over braincase during postembryonic ontogeny (6- 



Ctenosaura acanthura 

 No synapomorphies identified. 



Ctenosaura pectinata 

 No synapomorphies identified. 



