84 University of California Publications in Zoology 



detected in only some members of three species, C. clarki, C. hemilopha, and C. similis. 

 In Cyclura, the absence of a posterior coracoid fenestra was observed only in two out of 

 eight C. nubila, one of which lacked the fenestra unilaterally. 



According to Peterson (1973), the presence of a posterior coracoid fenestra is 

 associated with large size and/or the presence of a proximal belly of the M. biceps. 

 Because a posterior coracoid fenestra is present in the species of Ctenosaura that reach 

 smaller maximum sizes than Brae hy lop hus, in which the fenestra is absent, presence of the 

 fenestra cannot be strictly size-dependent. The association of the fenestra with a proximal 

 belly of the M. biceps was not examined in the present study. 



Although the evidence is somewhat ambiguous, outgroup comparison favors the 

 interpretation that the absence of posterior coracoid fenestrae is plesiomorphic for 

 iguanines. Basiliscines and oplurines invariably lack these fenestrae. Morunasaurs 

 generally lack posterior coracoid fenestrae, but in rare cases very small ones are present. 

 Crotaphytines generally possess posterior coracoid fenestrae, although they are 

 occasionally absent in Gambelia. If the general rather than the invariable presence or 

 absence of posterior coracoid fenestrae is considered to be the systematic character, then 

 outgroup comparison will either yield equivocal results or indicate that the absence of 

 posterior coracoid fenestrae is plesiomorphic, depending on the relationships among 

 iguanines and the four outgroups. 



Clavicles (Fig. 40). Iguanine clavicles are boomerang-shaped, paired bones lying 

 along the anterior margin of the pectoral girdle. They articulate ventromedially with the 

 anterior median end of the interclavicle and dorsolaterally with the anteroventral edges of 

 the suprascapular Compared with those of certain other iguanids, the clavicles of 

 iguanines are relatively simple, generally lacking sharp, ventrally directed processes (hooks 

 of Etheridge, 1964a) and ventromedial fenestrae, although small fenestrae are sometimes 

 present in Conolophus. 



Sauromalus differs from other iguanines in having slender clavicles, which are more or 

 less elliptical in cross section. The clavicles of other iguanines have thin lateral shelves, 

 making them wider when viewed anteriorly, although some Ctenosaura approach the 

 condition seen in Sauromalus. Because the clavicles of all outgroup taxa examined except 

 Oplurus quadrimaculatus are wide with thin lateral shelves, this condition must be 

 considered plesiomorphic for iguanines. 



Interclavicle (Fig. 40). This median, unpaired bone is the ventralmost in the pectoral 

 girdle. In iguanines it bears the shape of a "T" or an arrow, formed by a lateral process at 

 the anterior end on each side and a median posterior process. The anterior process seen in 

 certain other squamates (Lecuru, 1968b) is virtually absent. 



The extent of the posterior median process of the interclavicle varies among iguanines 

 and is here assessed by the location of the posterior tip of the bone relative to the lateral 

 comers of the sternum and the sternal attachments of the cartilaginous sternal ribs. 

 Amblyrhynchus and Sauromalus (Fig. 40C) have short interclavicles that do not extend 

 posteriorly beyond the lateral corners of the sternum, where the first pair of sternal ribs 

 attaches. In all other iguanines except Conolophus pallidus and Cyclura nubila the 



