Phylogenetic Systematics of I guanine Lizards 157 



supposed geographic ranges of the species and the actual geographic distribution of 

 specimens possessing the diagnostic characters of each species, Ray and Williams 

 (unpubl.) considered pectinata to be a synonym of acanthura. The primary character used 

 by Bailey (1928) to distinguish between these two taxa was whether the middorsal scale 

 row was continuous (pectinata) or interrupted {acanthura) in the sacral region, but Hardy 

 and McDiarmid (1969) claim that this character is variable within pectinata from western 

 Mexico. Nevertheless, synonymizing pectinata with acanthura on the basis of such data 

 rests on an assumption that the two taxa are not broadly sympatric. 



Stejneger (1901) described Ctenosaura bakeri from Utilla (Utila) Island, Honduras, and 

 Bailey (1928) surmised that it may also occur on Bonacca (Guanaja) and Ruatan (Roatan) 

 islands. Specimens collected subsequently on Roatan have been considered to be C. bakeri 

 (Wilson and Hahn, 1973; Meyer and Wilson, 1973), but they differ from the Utila 

 specimens in several ways (Table 10), including characters suggesting that they may not 

 even be one another's closest relatives. The populations from the two islands are probably 

 best considered separate species. 



Sauromalus Dumeril 1856 



Type species (by monotypy): Sauromalus ater Dumeril 1856. 



Etymology: (Greek) Sauros, lizard, + omalos, flat. 



Definition: The most recent common ancestor of the Recent species of Sauromalus 

 (ater, australis, hispidus, obesus, slevini, and varius) and all of its descendants. 



Distribution: Deserts of the southwestern United States in southeastern California, 

 southern Utah and Nevada, and western and central Arizona, southward into Mexico in 

 western Sonora and eastern Baja California as well as various islands in the Gulf of 

 California (Fig. 56). 



Diagnosis: Members of this taxon can be distinguished from other iguanines by the 

 following synapomorphies: 



1. Parietal foramen located variably within frontal (13-B). This character occurs also 

 in some populations of Ctenosaura and Cyclura; the parietal foramen is invariably located 

 within the frontal in Dipsosaurus and Cyclura carinata. 



2. Splenial relatively small (33-B). 



3. Angular does not extend far up labial surface of dentary and is not visible, or is only 

 barely visible in lateral view (37-B). This character also occurs in Amblyrhynchus and 

 Conolophus; thus, it is either convergent or a synapomorphy of a more inclusive taxon. 



4. Angular reduced and narrow posteriorly (38-B). 



5. Modal number of premaxillary teeth fewer than seven (absolute range 3-7; range of 

 modes for species 4-6) (43-44- A). This character also occurs in Ctenosaura defensor. 



