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University of California Publications in Zoology 



FIG. 35. Lateral views of the twentieth presacral vertebrae of (A) Sauromalus obesus (RE 1578) and (B) 

 Ctenosaura pectinata (RE 641), showing differences in the height of the neural spine. Scale equals 0.5 cm. 

 Abbreviations: con, condyle; ns, neural spine; pz, postzygapophysis; s, synapophysis. 



Sauromalus differs from other iguanines in the morphology of its presacral vertebrae. 

 In this genus, the neural spines of the presacral vertebrae are short (Fig. 35A); from the 

 base of the postzygapophysial articular surfaces to the top of the neural spine they measure 

 less than 50% of the total height of the vertebrae. In most other iguanines the neural spines 

 make up more than 50% of the total vertebral height (Figs. 34A, 35B), though there is 

 considerable variation in this category. This variation includes both interspecific 

 differences in adult morphology and ontogenetic increase in neural spine height within 

 species. Ctenosaura bridges the morphological gap between the two categories, with some 

 members (e.g., C. clarki) approaching the condition seen in Sauromalus. Outgroup 

 comparison yields equivocal results concerning the polarity of the different conditions of 



