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University of California Publications in Zoology 



B 



D 



FIG. 37. Dorsal views of caudal vertebrae of Dipsosaurus dorsalis (KdQ 22): (A) number 4, (B) number 

 9, (C) number 15, and (D) number 28. Scale equals 1 mm. Abbreviations: fp, fracture plane; ns, neural 

 spine; prz, prezygapophysis; tp, transverse process. 



process series and more frequently possess bilaterally asymmetrical transverse processes. 

 The transverse processes decrease in size posteriorly and, although the members of the 

 posterior pair are as large or larger than those of the anterior pair, it is usually the former 

 that disappear first (although the alternative is not uncommon), resulting in a third series 

 with a single pair of transverse processes (Fig. 37C). These processes, presumably 

 serially homologous with the anterior transverse processes of the second series, based on 

 their anterior position on the vertebrae, continue to decrease in size until they vanish, 

 leaving a fourth series whose vertebrae lack transverse processes (Fig. 37D). A variable 

 number of vertebrae at the end of this last series are nonautotomic. 



