Phylogenetic Systematics of I guanine Lizards 



27 



B 



FIG. 9. Dorsal views of the skulls of (A) Cyclura cornuta (AMNH 57878) and (B) Sauromalus obesus 

 (RE 467), showing differences in the relative sizes of the external nares and the presence or absence of 

 prefrontal contribution to the posterior margin of the nares. Prefrontal is shaded. Scale equals 1 cm. 



Boulenger (1890) noted that the contribution of this bone to the posterior margin of the 

 fenestra exonarina (Fig. 9A) distinguished Metopoceros cornutus (Cyclura cornuta) from 

 all other iguanines. In the other iguanines, maxilla and nasal meet anterior to the prefrontal 

 and exclude it from the margin of the fenestra (Fig. 9B). This condition is undoubtedly 

 plesiomorphic, since it is found in all basiliscines, crotaphytines, morunasaurs, and 

 oplurines, and in most other lizards (except varanoids, Shinisaurus, and chamaeleons). In 

 C. cornuta, contribution of the prefrontal to the margin of the fenestra exonarina is related 

 to enlargement of the latter. Although the prefrontals of other species with large bony 

 external nares do not enter the fenestra margin, none of these have bony external nares as 

 large as those of C cornuta. Because the apomorphic condition is found in only one 

 species of a genus containing eight, it provides no information about intergeneric 

 relationships. 



A large lacrimal foramen, bounded by the prefrontal medially and the lacrimal laterally, 

 pierces the anterior wall of the orbit (Fig. 10). Just posterior to the lacrimal foramen four 

 bones-lacrimal, jugal, palatine, and prefrontal-approach one another, and one of two 



