Phylogenetic Systematics of I guanine Lizards 167 



Amblyrhynchus . These characters indicate that Conolophus is monophyletic and thus, 

 contrary to one commonly entertained hypothesis about the relationships of the Galapagos 

 iguanas (Thornton, 1971; Higgins, 1978), cannot be considered ancestral to 

 Amblyrhynchus. 



IguaninaBell 1825 



Type genus: Iguana Laurenti 1768. 



Etymology: Modification of Iguana, the name of its type genus. 



Definition: The most recent common ancestor of Cyclura and Iguana and all of its 

 descendants. 



Distribution: Lowlands of the American mainland from Sinaloa and Veracruz, Mexico, 

 southward through Central America and northern South America to southern Brazil and 

 Paraguay as well as various Caribbean islands, including both the Greater and Lesser 

 Antilles. 



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

 following synapomorphies: 



1 . Squamosal abuts against dorsal end of tympanic crest of quadrate ( 19-B). 



2. Cristae ventrolaterales of parabasisphenoid only narrowly constricted behind 

 basipterygoid processes (28-B,-C). This character does not occur in Cyclura carinata. 



3. Surangular exposed laterally well anterior to apex of coronoid and often anterior to 

 last dentary tooth (39-B). This character also occurs in some Ctenosaura and may be a 

 synapomorphy of a more inclusive group. 



4. Crowns of posterior marginal teeth with five or more cusps (46-C,-D). This 

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

 group. 



Another possible synapomorphy of Iguanina is the development of a dewlap. Although 

 the dewlap of Cyclura is relatively small compared with that of Iguana, it is larger than that 

 of other iguanines QxcQpt Brachylophus and some Ctenosaura. 



Fossil record: The oldest known fossil referable to Iguanina is an almost complete 

 skull from the Pliocene of southern California (Norell, 1983). This and other fossil 

 Iguanina are discussed further in the sections on the fossil records of Iguana and Cyclura, 

 below. 



Comments: The name Iguanina is first used in this work; Bell (1825) is credited with 

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

 Code of Zoological Nomenclature). 



