146 University of California Publications in Zoology 



2. Medial borders of pterygoids curve sharply toward midline anterior to pterygoid 

 notch; pyriform recess narrows abrupdy (25-B). This character occurs also in Dipsosaurus 

 and may be a synapomorphy of a more inclusive group. 



3. Crowns of posterior marginal teeth with four or more cusps (46-B,-C, or-D). This 

 character occurs also in Dipsosaurus and some Brachylophus, and may be a synapomorphy 

 of all iguanines. It has reversed in Amblyrhynchus and some Ctenosaura. 



4. Posterior portion of pterygoid tooth patch displaced laterally away from medial 

 border of pterygoid (48-B). Pterygoid teeth are absent in most Conolophus, but when 

 present they lie away from the medial pterygoid border. This character develops during 

 postembryonic ontogeny and is not always evident in small specimens. 



5. Zygosphenes separated from prezygapophyses by a deep notch (56-B). This 

 character occurs also in Brachylophus and may be a synapomorphy of a more inclusive 

 group. 



6. Sequence of autotomic caudal vertebrae or that of vertebrae with two pairs of 

 transverse processes begins at or behind 10th caudal vertebra (61-B). The polarity of this 

 character is questionable. 



7. Posterior coracoid fenestra usually present (65-B). This character exhibits some 

 variation within basic taxa. 



8. Right and left systemic arches unite to form dorsal aorta posterior to heart (77-B). 



9. One or more circular colic valves present (80-B). This character occurs also in 

 Dipsosaurus and may be a synapomorphy of a more inclusive group. 



Fossil record: The earliest fossils that are clearly referable to Iguanini are from the 

 Pliocene of southern California. Among extant Iguanini these fossils appear to be most 

 closely related to Iguana (Norell, 1983). Stevens (1977) considered a dentary fragment 

 from the early Miocene of Texas to be either Ctenosaura or Sauromalus. If correctly 

 referred, this would be the oldest record of Iguanini. These and other fossil records are 

 given under the least inclusive taxa to which they belong or are most closely related. 



Comments: Although this is the first use of Iguanini, Bell (1825) is credited with 

 authorship under the principle of coordination (Article 36, third edition of the International 

 Code of Zoological Nomenclature). Iguanini contains all the really large iguanines, and 

 large body size may be an additional synapomorphy of this taxon. Some Ctenosaura are 

 relatively small, but this probably represents a secondary reduction in size (see comments 

 on Ctenosaura, below). Relationships among four recognizable monophyletic subgroups 

 of Iguanini are uncertain and are discussed in greater detail in the comments on Ctenosaura, 

 Sauromalus, Amblyrhynchina, Iguanina, and Cyclura. 



Ctenosaura Wiegmann 1 828 



Type species (subsequent designation by Fitzinger 1843): Ctenosaura cycluroides 

 Wiegmann 1828 = Lacerta acanthura G. Shaw 1802. 



