44 University of California Publications in Zoology 



medial borders of the pterygoids, though a moderate curvature occurs in some oplurines. 

 Thus, depending upon the relationships among ingroup and outgroups, either the polarity 

 of this character will be equivocal, or the interpretation that the relatively straight medial 

 border of the pterygoids is plesiomorphic will be favored. 



Ectoptery golds (Figs. 5A,B, 6A). Each ectopterygoid lies at the posterior margin of 

 the suborbital fenestra forming a brace between the jugal and maxilla anterolaterally and the 

 pterygoid posteromedially. Near the posteromedial comer of the suborbital fenestra, the 

 ectopterygoid may contact the palatine, usually on the dorsal surface of the palatal bones. 

 Contact between ectopterygoid and palatine in this region is the common condition only in 

 Conolophus among iguanines, and occurs in about half of the Iguana delicatissima 

 examined. This contact occurs rarely in some other iguanine species. Ectopterygoid- 

 palatine contact in this region was not observed in any of the four outgroups and is 

 therefore considered apomorphic. 



The ectopterygoid may also contact the palatine near the anterolateral comer of the 

 suborbital fenestra. This condition is clearly derived for iguanines on the basis of outgroup 

 comparison, but does not appear to be characteristic of any iguanine species. Only 

 Amblyrhynchus exhibits the anterolateral ectopterygoid-palatine contact commonly, but 

 even here it occurs in less than half of the specimens examined. Because the apomorphic 

 state of this character is not characteristic of any iguanine species and because diagnostic 

 apomorphies of Amblyrhynchus are plentiful, I have chosen to ignore this character in the 

 phylogenetic analysis. 



BRAINCASE 



The iguanine braincase (Figs. 5A,B, 6A), or neurocranium, is composed of four pairs of 

 endochondral bones-orbitosphenoids, prootics, opisthotics, and exoccipitals-and three 

 unpaired ones-basisphenoid, basioccipital, and supraoccipital. The parasphenoid, a dermal 

 bone, is also described here because of its intimate association with the basisphenoid. 

 Parasphenoid and basisphenoid as well as exoccipitals and opisthotics are fused to each 

 other even in juveniles, and all other elements except orbitosphenoids fuse with 

 neighboring braincase elements late in ontogeny. In some very large specimens, even the 

 orbitosphenoids are fused with one another. Although the stapes and epipterygoids are 

 splanchnocranial elements, they are included in this section because of their close 

 associations with the braincase. 



Orbitosphenoids (Fig. 19). The orbitosphenoids are paired, crescent-shaped bones 

 lying within the membranes that separate the brain cavity from the orbits. Each 

 orbitosphenoid is continuous with five orbital cartilages: the septal cartilage and planum 

 supraseptale anterodorsally, the pila accessoria and pila antotica posterodorsally, and the 

 hypochiasmatic cartilage ventrally (Oelrich, 1956). Although consistent differences in the 

 shapes of the orbitosphenoids exist between iguanine taxa, these differences seem to be 

 related to differences in body size. In large iguanines, the orbitosphenoids undergo 

 considerable ontogenetic changes in shape resulting from progressive outward ossification 



