Serradigitus Stahnke, 1974

Soleglad, Michael E. & Fet, Victor, 2008, Contributions to scorpion systematics. III. Subfamilies Smeringurinae and Syntropinae (Scorpiones: Vaejovidae), Euscorpius 71 (71), pp. 1-115 : 87

Genus Serradigitus Stahnke, 1974

Type Species. Vaejovis wupatkiensis Stahnke, 1940

[= Serradigitus wupatkiensis (Stahnke, 1940) ].

References (selected):

Serradigitus : Stahnke, 1974: 130–132, figs. 6C, 6D (in part); Williams & Berke, 1986: 351 (in part); Sissom, 1990a: 114 (in part); Sissom & Stockwell, 1 991: 197–214; Stockwell, 1992: 40 9, 416, figs. 19, 40, 42 (in part); Kovařík, 1998: 145 (in part); Sissom, 2000: 518–524 (in part); Soleglad & Fet, 2003b: 88 (in part); Soleglad & Fet, 2006: 26–27, 29, figs. 1–5, 12–14, 17–29, 33–40, 46; Graham & Soleglad, 2007: fig. 13.

Composition. This genus includes the following 19

species and subspecies:

S. adcocki (Williams, 1980) S. armadentis (Williams, 1980) S. baueri ( Gertsch, 1958)

S. bechteli (Williams, 1980) S. calidus (Soleglad, 1974) S. dwyeri (Williams, 1980) S. gertschi gertschi (Williams, 1968) S. gertschi striatus (Hjelle, 1970) S. gigantaensis (Williams, 19 80) S. gramenestris (Williams, 1970) S. haradoni (Williams, 198 0) S. hearnei (Williams, 1980) S. joshuaensis (Soleglad, 19 72) S. littoralis (Williams, 1980) S. minutis (Williams, 1970) S. pacificus (Williams, 1980) S. torridus Williams et Berke , 198 6 S. wupatkiensis (Stahnke, 1940) S. yaqui Sissom et Stockwell , 1 991

Distribution. Mexico (Baja California, Baja California Sur, Coahuila, Sonora), USA (Arizona, California, Nevada, Utah).

The range of the genus Serradigitus is disjunct (see map in Fig. 202 ): it includes the southwestern United States and Baja California peninsula, and mainland Mexico. Mexico represents its primary disjunction, with a small representation in central coastal Sonora; S. yaqui , and S. calidus found in Coahuila, Mexico. The most northern species are the type species S. wupatkiensis ranging into central Utah and S. gertschi striatus , found as far north as Mendocino County, California. The most southern species occur in Baja California Sur: S. minutis , S. adcocki , S. bechteli , S. armadentis , S. haradoni , and S. gigantaensis . The majority of Serradigitus species are found throughout Baja California, accounting for 12 endemic species (out of 19 species and subspecies); several species are limited to islands on both the Pacific and the Sea of Cortez, S. baueri , S. dwyeri , S. bechteli , and S. armadentis .

Diagnosis. Modification to basal pectinal teeth of female usually significant, lacking sensorial area variable, affecting 1–4 teeth, blunted and ovoid to swollen and elongated, with little or no distal angling; OD denticles serrated, indistinguishable after OD -3; distal denticle elongated and hook-like with “whitish patch”; inner accessory denticles (IAD) absent; subaculear spinoid tooth not present.

Taxonomic history. Stahnke (1974) established the genus Serradigitus based on former “wupatkiensis ” group of Vaejovis . Williams (1980) synonymized this genus back to Vaejovis , but later (Williams & Berke, 1986). reinstated it in reduced scope. Sissom & Stockwell (1991) provided a detailed study of Sonoran species. Beutelspacher (2000), without any reasoning, synonymized Serradigitus back to Vaejovis . Soleglad & Fet (2006) separated five species of Serradigitus as a new genus Stahnkeus , and included both genera in their new tribe Stahnkeini .

Discussion. Species in Serradigitus are small to medium in size, ranging from the smallest, S. minutis , S. dwyeri , S. gigantaensis , S. joshuaensis , and S. haradoni , 18–22 mm in length, to S. pacificus , S. adcocki , and S. wupatkiensis , 40 mm.

Serradigitus and its sister genus Stahnkeus exhibit the most exaggerated form of the modified basal pectinal teeth in the female and the serrated condition of the chelal fingers. Except for the occurrence of S. calidus in Coahuila and S. yaqui in coastal Sonora, this genus occurs primarily in California and Baja California and all species appear to be lithophilic.

Figures

Figure 202: General distribution of scorpion subfamily Syntropinae (tribe Stahnkeini) in North America with the ranges of genera Stahnkeus, Serradigitus, Gertschius, and Wernerius delineated.