Relationships of the Baja California Ground Snakes, Genus Sonora

Abstract

Sonora bancroftae Klauber, 1943, and S. mosaueri Stickel, 1938, are placed in the synonymy of S. semiannulata Baird and Girard, 1853. The characters that have been used to separate these taxa (color pattern, numbers of ventrals and subcaudals, and dorsal scale row reduction pattern) are shown to be insufficient for that purpose. Three species of Sonora presently are recognized as occurring in Baja California, M6xico, and the adjacent United States. S. bancroftae Klauber, 1943 (type locality: 2 mi. E San Jorge, Baja California Norte), is found in northwestern Baja California, and S. mosaueri Stickel, 1938 (type locality: Comondfi, Baja California Sur), is found in the southern half of Baja California. S. semiannulata Baird and Girard, 1853 (type locality: Sonora, restricted by Stickel, 1943, to the vicinity of the Santa Rita Mountains of southern Arizona, United States) is found in the southwestern quadrant of the United States and northern mainland Mexico, but in Baja California occurs only in the northeastern part, northward from the vicinity of Santa Rosalia (Stickel, 1943; Stebbins, 1966). These species have not been reviewed since Stickel (1938, 1943). In the intervening years, several specimens have been collected that improve our understanding of the relationships of these ground snakes. As first revised by Stickel (1938), the Sonora semiannulata complex (all Sonora except S. aemula and S. michoacanensis) contained five species: S. taylori (South Texas), S. episcopa (Great Plains), S. mosaueri (Baja California), S. semiannulata (western United States), and S. miniata (Idaho south to Arizona and California). The features used to diagnose these phenetically very similar species were temporal formula (1+1 in S. taylori and 1+2 in all others), numbers of ventrals and subcaudals, numbers of dorsal scale rows, and color pattern. Although Stickel was aware of color pattern polymorphism in S. episcopa and in S. semiannulata in the eastern part of its range, he distinguished western S. semiannulata from the largely sympatric