Phylogenetic Systematics oflguanine Lizards 129 



related to Iguana and Cyclura, while the lack of lateral contact between palatine and jugal 

 posterior to the infraorbital foramen (character 23-A) suggests that Sauromalus may be the 

 sister group of all other iguanines in the lower-level analysis. However, this character is 

 actually variable within Sauromalus and may have reversed within this taxon. 



Node 4, suggesting a sister-group relationship between Iguana and Cyclura, is 

 supported by four characters: squamosal abuts against dorsal end of quadrate (19-B); 

 cristae ventrolateralis of parabasisphenoid relatively widely separated (28-B or-C); 

 surangular extends far forward on lateral surface of mandible (39-B); and polycuspate or 

 serrate marginal tooth crowns (46-C or-D). One of these characters (46) actually suggests 

 monophyly of a more inclusive group consisting of Sauromalus, Iguana, and Cyclura. 

 Another character, absence of posterolateral processes on pleurapophyses of second sacral 

 vertebra (character 57-B), suggests a sister-group relationship between Iguana and 

 Ctenosaura, although most Cyclura also lack the processes. Yet another character, large 

 ventral process of the squamosal (18- A), suggests a sister-group relationship between 

 Amblyrhynchus and Iguana (the homology of this character is dubious but cannot be ruled 

 out on morphological grounds alone). 



Node 3, suggesting a sister-group relationship between Amblyrhynchus and 

 Conolophus, is the best-supported node. It is diagnosed by 10 derived characters: nasal 

 process of premaxilla covered dorsally between nasals (5-B); prefrontal contacts jugal 

 behind lacrimal foramen (7-B); frontal wider than long (8-B); reduction of lacrimal (17-B 

 or-C); medial crest on anterior dorsal surface of palatine (21-B); enlarged labial foot of 

 coronoid (36-B or-C); surangular covered lingually below coronoid (40-B); premaxillary 

 teeth with large lateral cusps (45-B); anterior portion of pterygoid tooth patch absent (50- 

 B); and pointed, conical dorsal head scales (83-B). Nevertheless, seven derived characters 

 suggest a sister-group relationship between Amblyrhynchus and Sauromalus: medial 

 separation of second ceratobranchials (54-B); reduction or loss of scapular fenestrae (65- 

 B); short posterior process of interclavicle (68-B); T-shaped interclavicle (69-B); reduction 

 or loss of sternal fontanelle (70-B); medial separation of xiphisterna (71-B or-C); and 

 quadrangular, nonoverlapping superciliary scales (84- A). Conolophus lacks all of these 

 derived characters. Therefore, if a sister-group relationship between Amblyrhynchus and 

 Conolophus is accepted, then the derived characters shared by Amblyrhynchus and 

 Sauromalus must either be convergent or reversed in Conolophus. 



