98 University of California Publications in Zoology 



denticulations are formed by enlarged keels on the anterior edges of the subdigital scales. 

 Varying degrees of enlargement of these keels are seen in iguanines. In Sauromalus the 

 anterior keels of the subdigital scales are nearly the same size as the posterior ones (the 

 subdigital scales are usually bi- or tricarinate), and the subdigital scales are roughly 

 bilaterally symmetrical with respect to the long axis of the toe (Fig. 45 A). In Dipsosaurus 

 and Iguana the anterior keels of the subdigital scales are slightly larger than their posterior 

 counterparts, and the subdigital scales are asymmetrical. Further enlargement of the 

 anterior keels and a concomitant increase in the asymmetry of the pedal subdigital scales is 

 seen in Amblyrhynchus, Conolophus, Brachylophus (Fig. 45B), and Cyclura (Fig. 45C) 

 (increasing in size roughly in that order). Much of this variation can be seen within 

 Ctenosaura. 



All subdigital scales do not exhibit equal enlargement of the keels, which are usually 

 largest under the first phalanx of digit II and the first and second phalanges of digit HI. 

 Cyclura and Ctenosaura defensor differ from other iguanines in that the scales bearing these 

 largest keels are fused at their bases, giving the scales the appearance of a comb when 

 viewed anteriorly (Fig. 45C). In Cyclura these combs are formed under the first phalanx 

 of digit II and the first and second phalanges of digit III (illustrated in Barbour and Noble, 

 1916: Plates 13-15); in Ctenosaura defensor they occur only under the first phalanx of digit 

 III. 



Enlargement of the anterior keels of the subdigital scales is present in all outgroups 

 examined in this study except basiliscines, though the degree of enlargement is variable. 

 Basiliscines cannot be compared with iguanines because they have but a single median keel 

 on the subdigital scales. In oplurines and crotaphytines the keels are moderately enlarged 

 as in Dipsosaurus, but in morunasaurs (especially Morunasaurus) they are very large. 

 Thus it is not possible to determine the precise plesiomorphic size of the keels of iguanines. 

 Nevertheless, two conditions seen in iguanines can be considered to be apomorphic. 

 Because the subdigital scales of all outgroups (except basiliscines) bear large anterior keels, 

 the small anterior keels and concomitant symmetry of the subdigital scales in Sauromalus 

 are apomorphic. Fusion of the bases of the subdigital scales with enlarged anterior keels is 

 not seen in any outgroup and must also be considered apomorphic. 



Hands and Feet. The hands and feet of Amblyrhynchus are partially webbed 

 (Boulenger, 1885), which is presumably related to the semi-aquatic habits of these lizards 

 and is unique among iguanids. 



Caudal Squamation. One of the supposedly diagnostic features of Ctenosaura is a tail 

 armed with strong, spinous scales (Bailey, 1928); however, similar caudal squamation also 

 occurs in most Cyclura (Barbour and Noble, 1916; Schwartz and Carey, 1977). Within 

 these two taxa the caudal squamation is highly variable among species. In some Cyclura 

 (e.g., C. cornuta), the caudal scales in adjacent verticils are of similar size and are not 

 spinous, a condition like that seen in most other iguanines. In the remaining Cyclura and in 

 Ctenosaura the tail bears whorls of enlarged, spinous scales at regular intervals along its 

 length. These whorls are separated by verticils of smaller scales that are smooth or much 

 less spinous (except the middorsal scale row). The number of verticils between the whorls 



