Phylogenetic Systematics of I guanine Lizards 



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FIG. 19. Anterolateral views of the left orbitosphenoids of three Iguana iguana-(A) RE 454, (B) JMS 

 245, (C) JMS 713-showing ontogenetic change in the shape of these bones resulting from progressive 

 ossification outward along the orbital cartilages. Scale equals 1 mm. Abbreviations: he, hypochiasmatic 

 cartilage; pac, pila accessoria; pan, pila antotica; pis, planum supraseptale. 



along the orbital cartilages (Fig. 19). Thus, the posterodorsal edge of each orbitosphenoid 

 first develops a posterior process where it joins the pila accessoria and pila antotica, and 

 this process later bifurcates following the two diverging orbital cartilages. The ventral and 

 anterodorsal ends of the bone elongate by a similar process and, in the case of the latter, the 

 two orbitosphenoids may eventually meet and fuse at the midline. Small iguanines 

 generally fail to develop the bifurcating posterodorsal processes of the orbitosphenoids 

 seen in adults of larger species, and I have never observed medial fusion of the two bones 

 at their anterodorsal ends in small iguanines. 



Epipterygoids (Fig. 6A). The epipterygoids are thin, rod-shaped bones extending from 

 the palate to the skull roof. Ventrally, the epipterygoids sit in depressions in the dorsal 

 surfaces of the palatines, but dorsally their articulations with the parietal are either weak or 

 lacking. I found no differences in epipterygoid morphology among iguanine genera that 

 might serve as systematic characters. 



Prootics (Fig. 6A). The paired prootics form the lateral walls of the neurocranium. 

 They are sutured to the supraoccipital dorsomedially, to the exoccipitals posteriorly, to the 

 basioccipital posteroventrally, and to the basisphenoid ventromedially. Although the 



