162 University of California Publications in Zoology 



8. Surangular not exposed, or only barely exposed on lingual surface of mandible 

 between ventral processes of coronoid (40-B). This character occurs also in Cyclura 

 cychlura, in which it is interpreted as convergent; it also occurs as a rare variant in several 

 other iguanines. 



9. Premaxillary teeth have large lateral cusps (45-B). 



10. Anterior portion of pterygoid tooth patch absent (50-B). The entire pterygoid tooth 

 patch is absent in most Conolophus and Dipsosaurus; however, when present, the 

 pterygoid teeth of Dipsosaurus lie along the medial border of the pterygoid, those of 

 Conolophus are located more laterally. 



11. Second ceratobranchials relatively short, often less than two-thirds the length of 

 the first ceratobranchials (52-53-A). This character also occurs in Sauromalus and is either 

 convergent or a synapomorphy of a more inclusive taxon. 



12. Caudal autotomy septa absent (60-B). This character also occurs in Brachylophus 

 and in Iguana delicatissima, in which it is interpreted as two separate instances of 

 convergence. 



13. Dorsal head scales pointed and conical (83-B). 



Fossil record: Steadman (1981) referred to Conolophus fossils of undetermined age 

 from a lava tube on Isla Santa Cruz, Galapagos. 



Comments: A close phylogenetic relationship between Amblyrhynchus and 

 Conolophus is widely accepted (Heller, 1903; Eibl-Eibesfeldt, 1961; Avery and Tanner, 

 1971; Thornton, 1971; Etheridge in PauU et al., 1976) but supporting evidence other than 

 geographic distribution has been scarce. Often the proposed close relationship between 

 these taxa was merely asserted or based on unspecified similarities. Avery and Tanner 

 (1971) did not distinguish between ancestral versus derived characters and used a highly 

 artificial system for assessing similarity (see Introduction). The immunological studies of 

 Higgins and Rand (1974, 1975; Higgins, 1977) compared the Galapagos iguanas only 

 with Iguana iguana among iguanines. Wyles and Sarich (1983) performed more extensive 

 immunological comparisons, including outgroups, but they prepared antisera to only four 

 of the ten iguanine taxa used in their study. The morphological data presented in this study 

 support the view that Amblyrhynchus and Conolophus are one another's closest living 

 relatives. 



The relationships of Amblyrhynchina to other Iguanini are uncertain. Although 

 members of Amblyrhynchina share two derived characters with Sauromalus-rQducQd lateral 

 exposure of the angular (37-B) and short second ceratobranchials (52- A)-i do not consider 

 this convincing evidence for a close relationship between these taxa. At least one other 

 character, highly cuspate marginal teeth (46-B,C), suggests a close relationship among 

 Sauromalus, Iguana, and Cyclura. Convergences between Amblyrhynchus and 

 Sauromalus are discussed in the comments on Sauromalus, above. 



