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University of California Publications in Zoology 



B 



vo 



fma 



vo 



FIG. 7. Posteroventral views of the premaxillae of (A) Amblyrhynchus cristatus (RE 1396), (B) 

 Cyclura cornuta (RE 383), and (C) Conolophus pallidas (RE 439), showing the small posterolateral 

 processes (arrows) of the premaxilla in Amblyrhynchus and the large lateral crests of the incisive process 

 that are pierced by foramina for the maxillary arteries in Conolophus. Scale equals 0.5 cm. Abbreviations: 

 fma, foramen for maxillary artery; ip, incisive process; vo, vomer. 



The premaxilla of Amblyrhynchus differs from that of basiliscines, crotaphytines, 

 morunasaurs, oplurines, and all other iguanines in several other ways. Its anterior edge 

 forms a nearly flat plate rather than being arched, and its nasal process is nearly vertical 

 instead of sloping backwards. 



The nasal process of the premaxilla, or the premaxillary spine, meets the nasals 

 posterodorsally (Figs. 5A, 6A, 8). In cross section this process is roughly triangular, with 

 the apex of the triangle pointing posteroventrally. The shape of this triangle varies 

 considerably, ranging from broad-based and low in Ctenosaura and Conolophus to 

 narrow-based in Amblyrhynchus, Dipsosaurus, and Sauromalus to nearly oval in Cyclura 

 cornuta. Differences between morphological extremes are great, but the extremes grade 

 more or less continuously into one another through intermediates; thus, there are no gaps to 



