Phylogenetic Systematics oflguanine Lizards 



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FIG. 8. Dorsal views of the preorbital portions of the skulls of (A) Sauromalus varius (RE 308), (B) 

 Ctenosaura hemilopha (RE 1964), and (C) Conolophus subcristatus (MVZ 77314), showing differences in 

 the degree to which the nasal process of the premaxilla is covered dorsally by the nasals. Scale equals 1.0 

 cm. Premaxilla is shaded. Abbreviations: mx, maxilla; na, nasal; prf, prefrontal. 



separate discrete character states. Furthermore, variation within Cyclura is greater than that 

 between many of the genera. For these reasons I have chosen not to use variation in the 

 cross-sectional shape of the premaxillary spine as a character in phylogenetic analysis. 



When viewed dorsally, the posterior exposure of the nasal process is variable within 

 iguanines (Fig. 8). In Brachylophus, Ctenosaura, Cyclura, Dipsosaurus, Iguana, and 

 Sauromalus, the nasal process of the premaxilla is exposed dorsally or covered only 

 slightly dorsolaterally by the nasals. Although differences in the extent of this overlap and 

 the length of the premaxillary spine yield strikingly different morphologies (Fig. 8A, B), 

 intraspecific variation in these features is too great to permit their subdivision into character 

 states. In Amblyrhynchus and Conolophus, however, one finds a condition not seen in 

 any other iguanine. The nasals of these genera cover the premaxillary spine posteriorly so 

 that the posteriormost portion of the spine that is visible dorsally falls short of the 

 transverse plane at the posterior ends of the fenestrae exonarinae (bony external nares or 



