Genus Serradigitus Stahnke 1974
Prosoma. – Anterior carapacial margin broadly V-shaped to essentially straight, with a subtle median indentation.
Mesosoma. – Pectinal tooth counts 13-27 in males, 11-23 in females. Proximalmost or proximal two pectinal teeth in females modified, either larger or smaller than the others and without sensorial areas.
Metasoma. – Dorsal carinae of segments I-IV with angular termination, sometimes with the distalmost denticle enlarged, subspinoid. Ventral submedian carinae of segments I-IV paired and variously developed, ranging from absent on all segments to granular to denticulate (strength and granulation usually increasing posteriorly). Segment V with linear ventromedian carina (i.e., not bifurcated distally).
Chelicerae. – Ventral margin of the cheliceral movable finger smooth; fixed finger ventral carina smooth. Serrula well developed distoventrally on movable finger.
Pedipalps. – Patella: Inner face with basal tubercles moderately developed; inner longitudinal carina present . Chelal carinae: Carinal development variable, some with all carinae developed and granular to denticulate, others with various carinae reduced, still others with all carinae absent. Chela dentition: Terminal denticles in most prominent, blade-like, and overlapping when fingers closed. Chela fixed finger with primary denticle row divided into two to five subrows of denticles, these are flanked by four to 18 (usually six) inner accessory denticles. Chela movable finger with primary denticle row divided into two to six subrows of denticles, these flanked by five to 20 (usually seven) inner accessory denticles. Denticles of denticle row variable, but in most consisting of narrow, elevated, sharp granules making the denticle row serrated in lateral view.
Trichobothrial Pattern. Patella with two ventral trichobothria along ventroexternal carina (the third ventral trichobothrium is positioned on the external face). Chela with four ventral (V) trichobothria. Chelal trichobothria ib positioned on the fixed finger, displaced distally to near the level of the sixth inner accessory denticle of the finger dentate margin or beyond. Chela finger trichobothrium est about equidistant between et and esb.
Legs. – Basitarsi and telotarsi in most species without setal combs. Telotarsi ventrally with a median row of small spinules that are flanked distally by one pair of slightly larger spinules. Ventromedian spinule row flanked laterally by setae.
Hemispermatophore. – Mating plug present, but lacking hooks on ental process. Lamellar process a bilobed flange, elevated on distal lamina and positioned on ectal margin.
Included species. – S. baueri (Gertsch, 1958); S. wupatkiensis (Stahnke, 1940); S. gertschi (Williams, 1968) with two subspecies, S. g. gertschi (Williams, 1970) and S. g. striatus (Hjelle, 1972); S. deserticola (Williams, 1970); S. gramenestris (Williams, 1970); S. harbisoni (Williams, 1970); S. minutis (Williams, 1970); S. joshuaensis (Soleglad, 1972); S. subtilimanus(Soleglad, 1972);S. calidus (Soleglad, 1974); S. adcocki (Williams, 1980); S. armadentis (Williams, 1980); S. bechteli (Williams, 1980); S. dwyeri (Williams, 1980); S. gigantaensis (Williams, 1980); S. haradoni (Williams, 1980); S. hearnei (Williams, 1980); S. littoralis (Williams, 1980); S. pacificus (Williams, 1980); S. torridus Williams & Berke, 1986; S. agilis Sissom & Stockwell, 1991; S. allredi Sissom & Stockwell, 1991; S. polisi Sissom & Stockwell, 1991; S. yaqui Sissom & Stockwell, 1991.
Similar taxa. – See Vaejovis C. L. Koch (nitidulus, mexicanus, and eusthenura groups).
Remarks. - This genus, with 24 species (one with two subspecies), developed through sequential addition of species to the Vaejovis wupatkiensis group, originally defined by Soleglad (1972). A key covering all Serradigitus species is unavailable. Workers must consult Williams (1980) for a key to the 13 species of Baja California and Sissom & Stockwell (1991) for a key to the Sonoran species. The genus includes some of the smallest species of vaejovids. Serradigitus are lithophilous inhabitants of rocky and boulder-strewn slopes, canyon walls and vertical cliff faces, seeking shelter in cracks and crevices during periods of inactivity. Although generally encountered in low elevation deserts, some inhabit mesic pine-oak or pine-juniper forests at moderate to high elevations (ca. 2500 m). They are typically uncommon and/or exhibit sporadic surface activity. Several new species should be found in northwestern México, especially in the Sierra Madre Occidental.
Included herein is the new genus Stahnkeus, proposed recently by Soleglad & Fet (2006) and placed in a new tribe Stahnkeini. Although the proposed genus shares apomorphic characters, its recognition renders the remainder of the Stahnkeini paraphyletic.