Phylogenetic Systematics oflguanine Lizards 



67 



FIG. 32. Corneal view of the left scleral ring of Ctenosaura similis (MCZ 9566). All iguanine species 

 typically exhibit the pattern of scleral ossicles illustrated: a total of 14 ossicles, with numbers 1, 6, and 8 

 positive (horizontal lines) and numbers 4, 7, and 10 negative (crosshatched). Scale equals 0.5 cm. 



and consists of basihyals, projecting anterolaterally from the body of the hyoid, and 

 ceratohyals, which run posteriorly from the distal ends of the basihyals. Basihyals fuse to 

 the hyoid body late in postembryonic ontogeny. Separate epihyals are not evident. Medial 

 to the ceratohyals lie the first ceratobranchials; these are the only bony elements of the 

 hyoid apparatus, the remainder being composed of calcified cartilage. The first 

 epibranchials extend posteriorly and dorsally from the posterior ends of the first 

 ceratobranchials. The second ceratobranchials lie medial to the first ceratobranchials and 

 extend direcdy posteriorly. Camp (1923) reported the presence of second epibranchials in 

 Iguana. Although I have never observed discrete second epibranchials in iguanines, the 

 delicate nature of these elements may have resulted in their destruction during skeletal 

 preparation. 



Differences exist among iguanine taxa in the relative lengths and the orientations of the 

 various hyoid elements (Fig. 33). The most obvious differences are seen in the second 

 ceratobranchials. In Ctenosaura, Cyclura, Dipsosaurus, and Iguana delicatissima, the 

 second ceratobranchials are of moderate size; they are generally more than two-thirds the 

 length of the first ceratobranchials, and never do they more than barely exceed the latter in 

 length (Fig. 33A). Although there is some overlap in the ranges of the relative lengths of 

 the second ceratobranchials between Amblyrhynchus, Conolophus, and Sauromalus, on 

 the one hand, and members of the previously described group, the second ceratobranchials 



