Phylogenetic Systematics of I guanine Lizards 165 



morphological features of Amblyrhynchus discussed in this paper are probably related to 

 this unique mode of existence. For example, the modifications of the teeth and colon may 

 be related to the unique diet of these lizards, which consists largely of marine algae 

 (Darwin, 1835; Carpenter, 1966; Dee Boersma, 1983). Derived characters obviously 

 associated with aquatic locomotion include the webbed digits and the strongly compressed 

 tail. The thickened stapes may be related to differences between the sound-transmitting 

 properties of water and air. The inflated nasal capsule and the deep pockets that develop on 

 the ventral surface of the frontal house enlarged nasal salt glands, which allow marine 

 iguanas to excrete excess salt accumulated from ingesting food with a salt concentration 

 similar to that of seawater (Schmidt-Nielsen and Fange, 1958). Convergences between 

 Amblyrhynchus and Sauromalus are discussed in the comments on the latter taxon, above. 



Conolophus Fitzinger 1843 



Type species (by original designation): Amblyrhynchus demarlii Dumeril and Bibron 

 1837 = Amblyrhynchus subcristatus Gray 1831b. 



Etymology: (Greek) Konos, cone, + lophos, crest, presumably referring to the conical 

 scales of the dorsal crest. 



Definition: The most recent common ancestor of Conolophus pallidus and C. 

 subcristatus and all of its descendants. 



Distribution: Islands of the Galapagos Archipelago, Ecuador (Fig. 57). 



Diagnosis: Members of this taxon can be distinguished from other iguanines by the 

 following synapomorphies: 



1. Lateral crests of premaxillary incisive process large and pierced or notched by 

 foramina for maxillary arteries (2-B). 



2. Crista cranii of frontal projects anteriorly forming a step rather than a smooth curve 

 where it meets medial edge of prefrontal at dorsal margin of orbitonasal fenestra (10-B). 



3. Supratemporals relatively small, extend one-half or less the distance across posterior 

 temporal fossae (14-B). 



4. Ectopterygoid contacts palatine near posteromedial comer of suborbital fenestra (26- 

 B). This character occurs also in about half of the Iguana delicatissima examined, in which 

 it is interpreted as convergent. 



5. Labial process of coronoid very large, extends more than two-thirds the way down 

 lateral surface of mandible in large specimens (36-C). 



6. Pterygoid teeth usually absent (51-B). This character also occurs in Dipsosaurus; 

 however, when present, the pterygoid teeth of Dipsosaurus lie along the medial border of 

 the pterygoid while those of Conolophus are situated more laterally. 



