McGUIRE-SYSTEMATICS OF CROTAPHYTID LIZARDS 101 Gambelia copei Gambelia wislizenii 120 Krn Arizona Sonora Fig. 50.-Geographic distribution of Gambelia copei. The small rectangular block in northern Baja California denotes the narrow zone where G. copei and G. wislizenii occur together. The asterisks represent sight records by the author for G. copei near Bahia de San Luis Gonzaga. The question marks along the Pacific coast of Baja California Sur indicate localities that must be considered questionable because of imprecise locality data.
102 BULLETIN CARNEGIE MUSEUM OF NATURAL HISTORY NO. 32 Il1usrrations.-Black-and-white photographs of adult lizards were provided in Banta and Tanner ( 1968) and Montanucci (1 978). Taxonotnic Remarks.-Gambelia copei and G. wislizenii are easily distinguished on the basis of their coloration (see diagnosis above). However, geographic variation in the dorsal coloration of Gambelia wislizenii is extensive and this alone is not particularly compelling evidence for the recog- nition of copei as a distinct species. The primary motivation for this taxonomic rearrangement is the occurrence of both forms in syntopy along a narrow zone within Paseo de San Matias in northeastern Baja California. Within Paseo de San Matias, in- dividuals that are easily identified to species occur together in the same microhabitat over a zone of 1.6 km without showing any obvious evidence of intergradation. Aside from this narrow contact zone, the distributions of G. copei and G. tvislizenii are widely separated. Paseo de San Matias is a low elevation dispersal corridor that connects the lower Colorado Desert with the coastal region of northwestern Baja Cali- fornia. Several desert species extend their ranges westward toward the Pacific coast by way of this corridor and some coastal species nearly reach the desert by extending eastward (Welsh and Bury, 1984). It may appear as though G. copei and G. tvislizenii are geographic variants and that the pat- tern change is the result of in situ selection where the habitat changes from extremely xeric creosote desert to more mesic mountainous terrain. How- ever, typical G. copei occur in the lower Colorado Desert region in the vicinity of Bahia de San Luis Gonzaga, documenting that the distinctive color pattern of G. copei is not another G. rvislizenii pat- tern type that appears only in mesic habitats. Gam- belia copei in the Bahia de San Luis Gonzaga region are approached by G. wislizenii in the vicinity of Puertocitos, where they are separated by a trans- verse volcanic field that is 31.5 road km in width. This lava field extends from the peninsular ranges to the edge of the Gulf of California and appears to be a dispersal bamer for Gantbelia. Because the color pattern differences noted above are main- tained in these populations, which occur in essen- tially identical habitats that are separated only by the lava field, the notion that the G. copei and G. wislizenii color pattern differences are the result of in situ selection is unlikely. Nevertheless, because this taxonomic decision is based only on differences in coloration that are relatively subtle, on a single osteological character that differs in frequency (the presence of a well-developed tubercle on the an- terolateral margin of the postorbital was present in all G. copei examined [n = 81, whereas in G. wisli- zenii, the tubercle usually is absent [present in four of 49 specimens]), and on presumed reproductive isolation in this region, the recognition of G. copei as a full species is considered tentative. Electropho- retic analyses of the Paseo de San Matias popula- tions are planned in order to determine if fixed al- lelic differences can be detected that are consistent with the dorsal color pattern data. Montanucci (1978) considered the populations of Gantbelia on Isla Tiburon and coastal Sonora be- tween Puerto Libertad and Bahia Kino to be con(sub)speci fic with copei. Although there are no- table similarities between certain individuals from the coastal Sonoran region and those from Baja Cal- ifornia (particularly in CAS 17050 from the south- eastern end of Isla Tiburon), they differ in that the Sonoran lizards have spots that continue onto the dorsal surface of the head, whereas G. copei nearly always lack this spotting. While some individuals from coastal Sonora clearly resemble those of Baja California, the majority examined here were char- acteristic of those of the remaining portions of So- nora. Gantbelia coronat Norell Gantbelia corona Norell, 1989:ll; fig. 10. Type locality: LACM locality 7058, Vallecito Badlands, Anza-Borrego Desert State Park (holotype: LACM 42880). Er)~mology.-From the Latin corona, a crown, in reference to the distinctive characteristics of the frontal and irontoparietal suture. Diagnosis. - Gambelia coronat is distinguished from other Gambelia by the presence of the fron- toparietal suture anterior to the posterior extent of the orbits. It is further distinguished from Gambelia copei and G. tvislizenii by the presence of a trans- versely concave frontal bone. Distribution. -Known only from the type locality. Rentarks. -Gambelia coronat is an extinct spe- cies known only from a fossilized skull and man- dibles. Black-and-white photographs of dorsal and lateral views of the skull were provided by Norell (1 989). Gambelia silus Stejneger Croraphytus silus Stejneger, 1890: 105. Typ locality: "Fresno, Cal." (holotype: USNM 1 1790A). Cruraphytus ~vislizenii-Cope, 1 900:255.
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