Phylogenetic Systematics oflguanine Lizards 37 



(Fig. 6A) and Dipsosaurus to the almost square ones of Ctenosaura (Fig. 14), Cyclura, and 

 Iguana (those of Sauromalus are intermediate). Although the extreme lacrimal 

 morphologies in iguanines other than Amblyrhynchus and Conolophus are very different, 

 the variation between them is more or less continuous. 



Basiliscines, crotaphytines, and oplurines all have relatively large lacrimals, but those 

 of morunasaurs are relatively small and may even be absent in some Morunasaurus. Thus, 

 it appears that a small lacrimal is apomorphic within iguanines, although the evidence is not 

 completely unambiguous. If so, then the small lacrimals of morunasaurs must be 

 convergent. 



Jugals (Figs. 5A, 6A, 14). The iguanine jugals form the ventral margins of the orbits 

 and are sutured anteriorly with the lacrimals, anteroventrally with the maxillae, medially 

 with the ectopterygoids, and posterodorsally with the postorbitals. Each jugal extends 

 posteriorly along the ventral border of the postorbital and variably contacts the squamosal 

 on the ventral surface of the upper temporal arch. This contact appears to be too variable 

 within genera to serve as a character for examining their interrelationships. 



Squamosals (Figs. 5A,C, 6A, 15). At the posterior end of each temporal arch, behind 

 the postorbitals, lie the squamosals. The shape of the squamosal is variable, ranging from 

 long and thin in Ctenosaura and Sauromalus to short and wide in Amblyrhynchus; the 

 remaining genera are intermediate. At its posterior end, the squamosal bears two 

 processes: a dorsal process that meets the supratemporal process of the parietal, and a 

 ventral process or peg directed towards the quadrate. The relative size of the ventral 

 process is variable, being more strongly developed in Amblyrhynchus and Iguana than in 

 the other genera (Fig. 15). In these two genera, however, the relationship of the ventral 

 process of the squamosal to the quadrate is different. As in most iguanines (Figs. 6A, 

 15 A), the ventral process of Amblyrhynchus (Fig. 15B) lies against the anterior edge of the 

 cephalic condyle of the quadrate, projecting into a gap or hole between this condyle and the 

 dorsal portion of the tympanic crest of the quadrate. In Iguana, the ventral process abuts 

 directly against the top of the tympanic crest (Fig. 15C), presumably reducing the mobility 

 of the quadrate. Cyclura possesses a potentially incipient stage to the condition seen in 

 Iguana. Its squamosal also abuts against the tympanic crest of the quadrate, but does so 

 more weakly because the ventral process is not as large (Fig. 15D). 



The relationship of the ventral process of the squamosal to the quadrate, and the relative 

 size of this process in basiliscines, crotaphytines, morunasaurs, and oplurines, are very 

 similar to those of Amblyrhynchus, suggesting that this condition is plesiomorphic for 

 iguanines. The unique articulation between squamosal and quadrate in Cyclura and Iguana 

 suggests that the large ventral process in Iguana may not be homologous with those of 

 Amblyrhynchus and non-iguanines. In order to maintain objectivity, however, I did not 

 assume that such was the case. 



Quadrates (Figs. 5B,C, 6A, 15). The quadrates lie at the posteroventral comers of the 

 skull. They are streptostylic and are important in jaw mechanics and feeding (Rieppel, 

 1978; K. K. Smith, 1980). Ventrally, each quadrate forms the articulation of the skull with 

 the articular bone of the mandible, and it also articulates dorsally with the squamosal, 



