Femtobuthus, Lowe, 2010

Lowe, Graeme, 2010, New picobuthoid scorpions (Scorpiones: Buthidae) from Oman, Euscorpius 93 (93), pp. 1-53 : 17

Genus Femtobuthus , gen. nov.

Type species. Femtobuthus shutuae , sp. nov.

Diagnosis. A member of the picobuthoid group (see diagnosis above), differentiated as follows: very small scorpions, adults <18 mm; metasoma ( Figs. 51–52 ) with segments I–III stout, ventral and ventrolateral carinae well developed, median lateral carinae weak, dorsal and dorsolateral carinae obsolete; ventrosubmedian carinae on II–III armed with enlarged dentate granules, lobate in females; metasoma IV–V wider, more robust than I–III; anterior ventral margins of metasoma III–IV rimmed by arcs of large rounded granules; metasoma V robust, dorsolateral carinae strong, ventrolateral carinae and ventral surface armed posteriorly with large, lobate granules; ventral and lateral surfaces of metasoma IV–V granular, not smooth, weakly pitted with shallow depressions; telson vesicle moderately swollen, ovoid; tibial spurs usually present on leg IV, sometimes present but often reduced or absent on leg III; fixed finger of chelicera armed ventrally with two denticles, distal denticle large, proximal denticle very small ( Fig. 54 ); pedipalps ( Figs. 47–50 , 62 ) with weak or obsolete carination, chela fixed finger weakly deflected upward at base, moderately curved, not strongly arched vertically ( Fig. 50 ); trichobothria ( Figs. 47–50 , 163–168 ): femur: 2 external, 2 dorsal (d 2, d 3 and d 5 absent), 2 internal (i 2 and i 4 absent); patella: 5 external (esb 2 and em absent), 4 dorsal (d 2 absent), 1 internal; manus: 4 external (Eb 3 and Esb absent), 2 ventral; fixed finger: 6 (esb absent).

Comparisons. This monotypic genus is created for one of the smallest known scorpions. The morphology of Femtobuthus is intermediate between Picobuthus , gen. nov., and Microbuthus . Characters shared with Picobuthus include: very small size, cheliceral fixed finger with proximal ventral denticle much smaller than distal ventral denticle, absence of smooth, pitted metasomal segments IV–V, stout pedipalp segments, lack of strongly arched pedipalp fingers, 5 external patellar trichobothria, and basitarsal bristle combs; characters shared with Microbuthus include: strongly trapezoidal carapace, relatively short, deep telson vesicle, and presence of tibial spurs on leg IV. It is distinguished from both Picobuthus and Microbuthus by subtractive neobothriotaxy of the pedipalp femur (2 dorsal, 2 internal trichobothria). Comparisons are summarized in Table 1.

Etymology. The name is derived from the prefix ‘ femto ’ which signifies a factor of 10 -15 in SI units, a reference to the very small size of these scorpions.

Figures

Figures 46–52: Femtobuthus shutuae, sp. nov., holotype male. 46. Carapace, dorsal aspect. 47. Right pedipalp femur, dorsal aspect. 48. Right pedipalp patella, dorsal aspect. 49. Right pedipalp patella, external aspect. 50. Right pedipalp chela, dorsoexternal aspect. 51–52, metasoma and telson. 51. Right lateral aspect. 52. Ventral aspect. Scale bar: 46: 1 mm; 47, 48, 49, 50: 0.70 mm; 51, 52: 1.37 mm.

Figures 53–62: Femtobuthus shutuae, sp. nov. 53–54, 58–59, paratype male from type locality; 55–57, 60–62, holotype male. 53–54, right chelicera. 53. Dorsal aspect. 54. Ventral aspect. 55. Right basitarsus and telotarsus III, retrolateral aspect. 56. Right telotarsus III, ventral aspect. 57. Left pectine, ventral aspect. 58–59, right hemispermatophore, lobes at base of flagellum. 58. Convex aspect. 59. Outer aspect. 60–61, right pedipalp chela movable finger terminus. 60. Dorsal aspect. 61. External aspect. 62. Right pedipalp chela, ventral aspect. Scale bar: 53, 54, 58, 59: 0.357 mm; 57: 0.76 mm; 55, 56, 60, 61, 62: 0.5 mm.

Figures 163–168: Trichobothrial map of Femtobuthus shutuae, sp. nov., holotype male. 163. Base of femur, internal aspect. 164. Femur, dorsal aspect. 165. Patella, dorsal aspect. 166. Patella, external aspect. 167. Chela, external aspect. 168. Chela, ventral aspect. Trichobothrial nomenclature after Vachon (1974), except for revised nomenclature in Figs. 126– 127.