46 



University of California Publications in Zoology 



B 



FIG. 20. Ventral views of the posterior portion of the palate and anterior portion of the braincase of (A) 

 Sauromalus varius (RE 308) and (B) Amblyrhynchus cristatus (RE 1508), showing differences in the length 

 of the parasphenoid rostrum. Scale equals 1 cm. Abbreviations: bptp, basipterygoid process; bs, 

 parabasisphenoid; pr, pyriform recess; ps, parasphenoid rostrum; pt, pterygoid. 



morphology of the prootics is complex, I have found no characters in these bones that 

 might serve to elucidate relationships among the basic taxa used in this study. 



Parabasisphenoid (Figs. 5B, 6A, 20, 21). Because the parasphenoid and basisphenoid 

 of iguanines are always fused postembryonically, I describe them as a single element. The 

 parasphenoid rostrum extends anteriorly like a thin, flat blade from the main body of the 

 parabasisphenoid on the midline. Compared to those of all other iguanines as well as those 

 of basiliscines, crotaphytines, morunasaurs, and oplurines, the parasphenoid rostrum of 

 Amblyrhynchus is relatively short (Fig. 20). Even the parasphenoid rostra of other short- 

 skulled taxa, such as the basiliscine Corytophanes, are much longer. 



The main body of the parabasisphenoid is an unpaired median bone that forms the 

 anterior floor of the brain cavity. It is sutured with the prootics laterally and with the 

 basioccipital posteriorly. Anterolaterally, two large basipterygoid processes meet the 

 anteromedial surfaces of the quadrate processes of the pterygoids at the pterygoid notches, 

 forming a movable joint between palate and braincase. 



Boulenger (1890) first noted variation in the form of the parabasisphenoid (Fig. 21) 

 among different iguanines. In most iguanines, the ventrolateral edges of the 

 parabasisphenoid, the cristae ventrolaterals, are strongly constricted behind the 



