148 University of California Publications in Zoology 



2. Posterolateral processes of parabasisphenoid absent or relatively small (29-B). 



3. Posterolateral processes on pleurapophyses of second sacral vertebra absent (57-B). 

 This character also occurs in Iguana and most Cyclura, and may be a synapomorphy of a 

 more inclusive group. 



4. One subocular scale very long (85-C). The polarity of this character is 

 questionable. An elongate subocular occurs also in Dipsosaurus, in which it is interpreted 

 as convergent. 



5. Tail bears whorls of enlarged, spinous scales (94-B). This character occurs also in 

 most Cyclura, in which it is interpreted as convergent. 



Other derived characters occur only in some Ctenosaura and may provide useful 

 information concerning relationships within this taxon: 



1. Prefrontal contacts jugal behind lacrimal foramen (7-B). This character also occurs 

 in Amblyrhynchus, Conolophus, and some Cyclura; within Ctenosaura, prefrontal-jugal 

 contact is characteristic only of C clarki and may be a synapomorphy of that taxon. 



2. Crista cranii forms step rather than smooth curve between frontal and prefrontal (10- 

 B). This character also occurs in Conolophus; within Ctenosaura it occurs only in C. 

 defensor and may be a synapomorphy of that taxon. 



3. Parietal foramen located entirely within frontal (13-B). This character occurs also in 

 Dipsosaurus and in some Cyclura and Sauromalus; within Ctenosaura it varies as much 

 within species as among them, and it is therefore uninformative about relationships among 

 these species. 



4. Infraorbital foramen located entirely within palatine (24-B). This character also 

 occurs in Brachylophus and in some Amblyrhynchus and Sauromalus; within Ctenosaura it 

 varies as much within species as among them, and it is therefore uninformative about 

 relationships among these species. 



5. Surangular extends anteriorly well beyond coronoid apex and sometimes beyond 

 posteriormost dentary tooth (39-B). This character occurs also in Iguana and Cyclura; its 

 pattern of variation within Ctenosaura needs further study. 



6. Crowns of posterior marginal teeth polycuspate (46-C). This character occurs also 

 in Iguana, Cyclura, and Sauromalus; within Ctenosaura it occurs only in C. defensor and 

 may be a synapomorphy of that taxon. 



7. Crowns of posterior marginal teeth tricuspid (46- A). Within Ctenosaura this 

 character, a presumed reversal, occurs in C. bakeri and C. quinquecarinata. 



8. Posterior portion of pterygoid tooth patch doubles ontogenetically (49-B). This 

 character, or a further modification of it, occurs also in Iguana and some Cyclura. Since 

 members of the small species of both Ctenosaura and Cyclura do not exhibit ontogenetic 

 doubling of the tooth row, and since small maximum size in these taxa is thought to be 

 derived (see comments on Iguanini, above), it is likely that this character is a 

 synapomorphy at a higher level and that failure to double the pterygoid tooth row is derived 

 within Ctenosaura. 



9. Fewer than 40 caudal vertebrae (59-B). This character also occurs in Sauromalus; 

 within Ctenosaura it occurs in C. clarki and C defensor. 



