Phylogenetic Systematics of I guanine Lizards 1 59 



13. Scapular fenestrae small or absent (65-B). This character occurs also in 

 Amblyrhynchus, in which it is interpreted as convergent. 



14. Clavicles narrow, the lateral shelf small or absent (67-B). 



15. Posterior process of interclavicle does not extend beyond lateral comers of sternum 

 (68-B). This character also occurs in Amblyrhynchus, in which it is interpreted as 

 convergent. 



16. Lateral processes of interclavicle form angles of between 75° and 90° with posterior 

 process, interclavicle roughly T-shaped (69-B). This character also occurs in 

 Amblyrhynchus, in which it is interpreted as convergent. 



17. Sternal fontanelle small or absent (70-B). This character occurs also in 

 Amblyrhynchus, in which it is interpreted as convergent. 



18. Sternum pentagonal; xiphistema widely separated (71-B). This condition is 

 approached in Amblyrhynchus. 



19. Pelvic girdle short and broad (72-B). 



20. Anterior iUac process small (73-B). 



21. Heart extends posterior to transverse axillary plane (75-B). 



22. Rostral scale divided by a median suture (81-B). 



23. Superciliary scales quadrangular and non-overlapping (84- A). This character also 

 occurs in Amblyrhynchus, in which it is interpreted as convergent. 



24. Enlarged anterior auricular scales (85-B). 



25. Middorsal scale row absent (89-B). 



26. Anterior and posterior keels of subdigital scales approximately equal in size; 

 subdigital scales roughly symmetrical with respect to long axis of toe (91-B). 



27. Body strongly depressed (95-B). 



Another possible synapomorphy of Sauromalus is the failure of the lateral edges of the 

 parietal table to meet ontogenetically. This character occurs also in Dipsosaurus and in 

 some Brachylophus, Ctenosaura, and Cyclura. 



In addition, the following derived characters occur in some Sauromalus: 



1. Lateral process of palatine behind infraorbital foramen fails to contact jugal (23-A). 

 This reversal occurs variably within ater, hispidus, and varius. 



2. Infraorbital foramen located entirely within the palatine (24-B). This character 

 occurs also in Brachylophus and in some Amblyrhynchus and Ctenosaura. Within 

 Sauromalus it is known only in obesus, and its occurrence is variable in this taxon. 



3. Coeliac artery originates between mesenteric arteries (78-B). This character occurs 

 also in Iguana. Its pattern of variation is poorly known, owing to small samples. 



Fossil record: Estes (1983) summarized information on fossil Sauromalus, and 

 additional material has been described subsequendy by Norell (1986). The oldest fossils 

 referred to this taxon are from the Pleistocene of California, Nevada, and Arizona. Stevens 

 (1977) referred a fragment of a left dentary from the lower Miocene of Texas to either 

 Ctenosaura or Sauromalus, but thought that it was probably closer to Ctenosaura. 



