26 University of California Publications in Zoology 



nasal fossae). In Cyclura cornuta, C. pingius, and Iguana delicatissima, the visible portion 

 of the nasal process of the premaxilla also fails to reach this plane; however, this condition 

 results from enlargement of the nasal fossae in these species rather than from increased 

 overlap of the premaxillary spine by the nasals. 



Basiliscines, oplurines, and morunasaurs generally have the nasal process of the 

 premaxilla exposed dorsally, at least along the midline. In crotaphytines, more extensive 

 overlap of the premaxillary spine by the nasals may occur, but never to the extent seen in 

 Amblyrhynchus and Conolophus. 



Nasals (Figs. 5 A, 6A, 8). This pair of bones lies along the midline of the skull roof 

 immediately posterior to the fenestrae exonarinae, forming the roof of the nasal capsule. 

 The relative size of the nasals varies considerably among iguanines. Brachylophus, 

 Conolophus, Ctenosaura, most Cyclura, Dipsosaurus, Iguana iguana, and Sauromalus 

 exhibit a condition that is widespread outside of the iguanines in which the nasals are of 

 moderate size. In Conolophus the nasals are subequal to the frontals in length, and in the 

 remaining taxa the nasals are shorter than the frontals. The nasals of Amblyrhynchus are 

 greatly enlarged, accompanying the enlargement of the entire nasal capsule. The increased 

 size of the nasal capsule probably enables it to house the large nasal salt glands of this 

 species (figured by Dunson, 1969, 1976). Because enlargement of the nasals is one 

 component of enlargement of the nasal capsule, I did not treat the two as separate 

 characters. 



The relative size of the nasals is also correlated with the size of the fenestrae exonarinae 

 (Fig. 9). In some species of Cyclura, most notably C. cornuta (Fig. 9A) and C. pinguis, 

 and in Iguana delicatissima, enlargement of the fenestrae exonarinae results from 

 emargination at the anterior edges of the nasals, reducing the relative size of these bones. 

 Because this apomorphic condition occurs only in some Iguana and Cyclura, I have not 

 used it for analyzing intergeneric relationships. The feature may, however, provide useful 

 information for uncovering relationships within these genera. 



Septomaxillae (Fig. 6A). The septomaxillae are thin, paired bones lying in the anterior 

 portion of the nasal capsule on either side of the nasal septum. These bones rest atop the 

 vomers and, except in Iguana delicatissima, they contact the roof of the nasal capsule 

 (premaxilla or nasals) dorsally. In most iguanines, each septomaxilla is relatively flat on its 

 dorsal surface, though a low ridge often appears near the lateral edge of the bone. Unlike 

 all other iguanines, the septomaxillae of Amblyrhynchus bear sharp longitudinal crests on 

 their anterodorsal surfaces. These crests appear to be apomorphic, since they are absent in 

 all four outgroups. The septomaxillae of crotaphytines and oplurines are similar to those of 

 iguanines in that they each send a long shelf posterodorsally. Those of morunasaurs and 

 Basiliscus are relatively small and are folded to form a transverse ridge. The septomaxillae 

 of Laemanctus are very small, and those of Corytophanes are possibly absent. A dorsal 

 septomaxillary crest is seen in some morunasaurs, but this crest is entirely different from 

 that of Amblyrhynchus, extending transversely rather than longitudinally. 



Prefrontals (Figs. 5A, 6A, 8, 9). The prefrontals have roughly the shape of a 

 triangular pyramid whose apex forms the posterolateral comer of the nasal capsule. 



