Abstract 



Iguaninae is a monophyletic taxon of tetrapodous squamates (lizards) that can be 

 distinguished from other iguanians by at least five synapomorphies. Skeletal variation 

 within Iguaninae is described and forms the basis of systematic characters used to 

 determine phylogenetic relationships among eight basic taxa, the currendy recognized 

 iguanine genera. Evolutionary character polarities are determined by comparison with four 

 closely related taxa, basiliscines, crotaphytines, morunasaurs, and oplurines. 



The distributions of derived characters among iguanine taxa suggest that: (1) Either 

 Brachylophus or Dipsosaurus is the sister group of the remaining iguanines (Iguanini). (2) 

 Dipsosaurus is a monophyletic taxon diagnosed by at least six synapomorphies. (3) 

 Brachylophus is a monophyletic taxon diagnosed by at least eight synapomorphies. (4) 

 Iguanini, containing Amblyrhynchus, Conolophus, Ctenosaura, Cyclura, Iguana, and 

 Sauromalus, is a new monophyletic taxon diagnosed by at least three synapomorphies. (5) 

 vWithin Iguanini, the relationships among four t2Lxa.-Ctenosaura, Sauromalus, 

 Amblyrhynchina, and Iguanina-are unresolved. (6) Ctenosaura is a monophyletic taxon 

 'diagnosed by at least three synapomorphies. (7) Enyaliosaurus is monophyletic, but it is a 

 subgroup of Ctenosaura rather than a separate taxon. If Enyaliosaurus is separated from 

 Ctenosaura, then Ctenosaura is not monophyletic. (8) Sauromalus is a monophyletic taxon 

 diagnosed by at least 24 synapomorphies, many of which are convergent in 

 Amblyrhynchus. (9) Amblyrhynchina is a new monophyletic taxon containing the 

 Galapagos iguanas Amblyrhynchus and Conolophus, and is diagnosed by at least 1 1 

 synapomorphies. (10) Amblyrhynchus is a monophyletic taxon diagnosed by at least 28 

 synapomorphies and is perhaps the most divergent iguanine from the most recent common 

 ancestor of all of them. Many of the unique features of Amblyrhynchus appear to be 

 related to its unique natural history. (11) Conolophus is a monophyletic taxon diagnosed 

 by at least eight synapomorphies and cannot, therefore, be considered ancestral to 

 Amblyrhynchus. (12) Iguanina is a new monophyletic taxon composed oi Iguana and 

 Cyclura and is diagnosed by at least three synapomorphies. (13) Iguana is a monophyletic 

 taxon diagnosed by at least seven synapomorphies. (14) Monophyly of Cyclura is a 

 problem in need of further study. Although three ostensible synapomorphies support 

 monophyly of Cyclura, other derived characters suggest that some Cyclura shared a more 

 recent common ancestor with Iguana than with other Cyclura. 



Summaries of Iguaninae and its monophyletic subgroups down to the level of the eight 

 basic taxa are provided; each summary includes the type of the taxon, etymology of the 

 taxon name, a phylogenetic definition, geographic distribution, a list of diagnostic 

 synapomorphies, the fossil record, and various comments. 



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