Phylo genetic Systematics of I guanine Lizards 75 



two characters in the sacra of iguanines, both involving the pleurapophyses of the posterior 

 sacral vertebra. 



The posterior edges of the pleurapophyses of the posterior sacral vertebrae of iguanines 

 may or may not bear posterolaterally directed processes (Hofstetter and Gasc, 1969: Fig. 

 50). These processes are usually present, though not invariably so, in Amblyrhynchus, 

 Brachylophus, Conolophus, Dipsosaurus, and Sauromalus, and are present in the single 

 specimen of Cyclura pinguis examined; they are absent in Ctenosaura, Iguana, and other 

 Cyclura. When present, each process lies posteroventral to a foramen in the posterior 

 surface of the second pleurapophysis. Occasionally, a process may develop dorsolateral to 

 the foramen; this process and the one described previously do not seem to be homologous 

 on positional grounds. 



Given the outgroups used in this study and their uncertain relationships, outgroup 

 analysis is useless for assessing the plesiomorphic condition of this character. The 

 processes are absent in basiliscines and Hoplocercus, present in the Enyalioides, variably 

 present in Oplurus, Chalarodon, Gambelia, and Morunasaurus, and present in 

 Crotaphytus. Therefore, I did not employ this character in phylogenetic analysis at the 

 level of all iguanines. 



The canal leading to the foramen that emerges alongside the posterior edge of each 

 posterior sacral pleurapophysis has its medial opening on the ventral surface of the same 

 pleurapophysis. This ventral foramen is almost always present in all iguanines except 

 Conolophus. In Conolophus, the ventral foramen may also be present, but more often it is 

 absent, and an open groove is left in place of the enclosed canal. The condition seen in 

 Conolophus is almost certainly apomorphic, since all four outgroups generally possess the 

 foramen and enclosed canal. 



Caudal Vertebrae (Figs. 37, 38). Iguanine caudal vertebrae are highly variable, but 

 possess many common structural features. The neural spines of the anterior caudal 

 vertebrae are taller than their presacral counterparts, but they gradually decrease in size 

 posteriad and increase their posterior orientation until they vanish toward the end of the tail. 

 Complete haemal arches, positioned intercentrally, begin between the centra of the second 

 and third or the third and fourth caudal vertebrae. They are oriented posteroventrally and, 

 like the neural spines, decrease in size and increase in posterior orientation, moving 

 posteriorly, until they vanish near the end of the tail. The bases of the haemal arches may 

 form continuous basal bars or they may be separate. Small, paired elements, presumably 

 serially homologous with the bases of the haemal arches, or otherwise incomplete haemal 

 arches, often precede the first complete arch. 



Four vertebral series (Fig. 37) can be recognized in the caudal sequence of iguanines 

 (Etheridge, 1967). The anterior seven to fifteen caudal vertebrae bear a single pair of 

 laterally or posterolaterally oriented transverse processes (fused caudal ribs) and lack 

 autotomy septa (fracture planes) (Fig. 37A). In the following series, each vertebra bears 

 two pairs of transverse processes that are either parallel or diverge from one another (Fig. 

 37B). The vertebrae in this second series and the remaining two series may or may not 

 have autotomy septa. Species that lack autotomy septa generally have a shorter double- 



