Physoctonus Mello-Leitao 1934

Physoctonus Mello-Leitão, 1934

Figures 1 E, 2 D, 9, 10D, 11G, 12F, 16A, B, 17D, 20A, B, 21G, 22G, 24S–U, 48–52

Vaejovis debilis C.L. Koch, 1840 [= Physoctonus debilis (C.L. Koch, 1840)], type species, by subsequent designation.

Vaejovis (part): C.L. Koch, 1840: 21, 22, pl. CCLIX, fig. 605; Kraepelin, 1899: 96.

Waejovis (lapsus): Gervais, 1844 b: 458.

Rhopalurus (part): Borelli, 1910: 5–8, fig. 1; Mello-Campos, 1924 a: 252, 275–277; Mello- Leitão, 1932: 14, 30; Meise, 1934: 42; Prado, 1940: 26, 29, 30; Mello-Leitão, 1945: 266, 272, 273; Bücherl, 1959: 268; 1971: 327; Francke, 1977 a: 125, 127–134, figs. 1–15; Lourenço, 1982 a: 108, 133, 135–137, fig. 78; Armas, 1984: 8; Lourenço, 1986 a: 133, 135, figs. 12, 16; 1986b: 165, fig. 7; 1990: 161; 1992: 55; Kovařík, 1998: 118; Lourenço, 2002: 101, 111, figs. 225, 226; Lira-da-Silva et al., 2005: 1, 2; Teruel, 2006: 51; Ubinski et al., 2016: 122.

Physoctonus Mello-Leitão, 1934 b: 76, 77, figs. 1–7; 1942: 129; 1945: 129–132, figs. 40, 41; Bücherl, 1967: 115; 1969: 768; Vachon, 1963: 161, 165; Stahnke, 1974: 129; Francke, 1977 a: 127; Lourenço, 2007: 359–364; Outeda-Jorge et al., 2009: 43–46; Prendini et al., 2009: 222; Brazil and Porto, 2010: 50, 57.

DIAGNOSIS: Physoctonus differs from other rhopalurusine genera by the obsolete carapacial carinae, the asetose proximal dorsal fulcra of the pectines, the simple (nonbifurcate) prolateral pedal spur of leg I, and the oblique subrows of primary denticles on the pedipalp chela fingers flanked by small, widely spaced prolateral accessory (supernumerary) denticles and sparse retrolateral accessory denticles. It differs further from Heteroctenus, Ischnotelson, gen. nov., Jaguajir, gen. nov., Rhopalurus, and Troglorhopalurus by the small size (total length, 20–25 mm); from Heteroctenus, Ischnotelson, Jaguajir, and Rhopalurus by the slender pedipalp chela manus of the adult male; from Heteroctenus, Jaguajir, and Rhopalurus by the absence of a pecten-sternite stridulatory organ; from Heteroctenus by the absence of depressions in the male pectinal plate and the presence of a subaculear tubercle on the telson; from Ischnotelson by the separate (unfused) lateral ocular and central lateral carinae of the carapace and the telson vesicle not laterally compressed; and from Troglorhopalurus by the proximal dentate margin of the chela fixed and movable fingers of the adult male emarginate, with a distinct gap evident between them, when closed.

DESCRIPTION: The following general description outlines characters common to both species of Physoctonus (for measurements, see table 3).

Total length: Relatively small scorpions (total length, 20–25 mm).

Color: Base color pale to dark yellow (fig. 1E). Carapace immaculate except interocular surface infuscate, forming dark triangle. Tergites immaculate except for dorsomedian band of infuscation, forming longitudinal stripe on mesosoma. Coxosternal region, pectines, and sternites immaculate, pale to dark yellow. Metasomal segments I–III, dorsal surfaces immaculate, yellow, similar color as carapace and tergites, segments IV and V, dorsal surfaces darker than preceding segments; I–III, ventral surfaces slightly darker than dorsal surfaces, IV and V noticeably darker than I–III, V darker than IV; I–IV each with dark ventromedian band of infuscation. Telson vesicle yellow, similar to metasomal segment V, aculeus almost black. Chelicerae, pedipalps, and legs base color yellow, similar to tergites, with reticulate infuscation; chela fingers dark brown.

Chelicerae: Base, dorsal surface with medial transverse row of well-developed tubercles.

Carapace: Median ocular tubercle low (fig. 16A, B); two median ocelli; three pairs of lateral macroocelli; one pair of lateral microocelli. Anteromedian, median ocular, and posteromedian sulci present, forming single, almost continuous, longitudinal sulcus. Carinae obsolete, finely granular, and barely distinguishable from surface granulation; lateral ocular and anterior central submedian carinae separate (unfused); central lateral and posterior central submedian carinae fused.

Pedipalps: Pedipalp femur retrolateral accessory carinae present. Pedipalp chela manus of adult male slender, proximal dentate margins of fixed and movable fingers slightly curved proximally (fixed finger curved dorsally, movable finger curved ventrally), such that proximal dentate margin emarginate, slight gap present between fingers proximally, when closed (fig. 48A, C), manus of female not incrassate, fixed and movable fingers not curved proximally, such that proximal dentate margin sublinear, little or no gap present between them proximally, when closed (fig. 48B); manus, proventral carina absent, promedian carina present; fixed and movable fingers, median denticle rows each comprising eight oblique subrows of primary denticles flanked by small, widely spaced prolateral accessory (supernumerary) denticles and sparse retrolateral accessory denticles; movable finger without proximal lobe (fig. 17 D). Pedipalps orthobothriotaxic Type A, α configuration; femur with five dorsal trichobothria, trichobothrium d 2 situated on prolateral surface; patella trichobothrium d 3 situated retrolateral to dorsomedian carina; chela fixed finger trichobothrium db proximal to or aligned with trichobothrium et.

Legs: Legs III and IV, tibial spurs absent; I and II, basitarsi each with simple prolateral pedal spur; telotarsi each with distinct pro- and retroventral rows of fine, acuminate macrosetae.

Pectines: Pectinal plate without depressions (male), anterior margin with sulcus (fig. 20A, B). Pectines not proximally expanded; proximal dorsal fulcra asetose; pectinal teeth almost straight, slightly curved laterally, proximal teeth, dorsal surfaces without striations but covered with small denticles, dorsobasal surfaces without macrosetae; pectinal sensillae short and blunt (figs. 11G, 12F).

Mesosoma: Tergites V–VII slightly wider than than I–IV; I–VI unicarinate, dorsosubmedian carinae absent, dorsomedian carina reduced to posterior half on I–VI, complete on V and VI. Tergite VII pentacarinate, dorsomedian carina complete (fig. 51). Sternites smooth, carinae absent or obsolete; sternite III, lateral margins not forming smooth, raised carina, ventromedian carina not elevated anteriorly, ventrosubmedian surfaces not forming paired depressions, smooth; respiratory spiracles (stigmata) width less than 5× length (fig. 10E).

Metasoma: Metasoma slender, increasing slightly in width posteriorly, segment V only slightly wider than I in adult male, I and V similar width in adult female (figs. 49, 50). Segments I–III each with 10 distinct, granular carinae, IV with eight distinct, granular carinae, V with five distinct, granular carinae; dorsosubmedian carinae obsolete, reduced to rows of granules on dorsal surfaces of segments I–IV, more pronounced on segment I; dorsolateral carinae complete on segments I–IV, and terminating in slightly larger, subspiniform granules posteriorly on II–IV, absent on V; lateral supramedian carinae complete on segments I–V; lateral inframedian carinae complete on segments I–III, complete but obsolete on IV, and absent on V; ventrosubmedian carinae complete on segments I–IV, absent on V; ventromedian carina absent on segments I–IV, complete on V. Intercarinal surfaces finely and densely granular on lateral and ventral surfaces of segments I–V and dorsal surfaces of I–III.

Telson: Vesicle oval, not laterally compressed, narrower than metasoma V; anterodorsal lateral lobes prominent; lateral and ventral surfaces granular, pentacarinate with distinct ventromedian carina; subaculear tubercle vestigial.

Hemispermatophore: Flagelliform; flagellum, elongate and narrow (fig. 24S–U); trunk concave; three lobules, ental (LI), ectal (LE), and basal (LB); LI inclined to ental side of trunk and continuous to flagellar base; flagellar base wide, ca. two thirds width of trunk; LE length ca. half that of LI, spiniform with curved tip; LB base wide and slightly elongate, apex thin and curved.

Cytogenetics: The diploid chromosome number of P. debilis (table 2) is 2n = 26 (Ubinski et al., 2016).

INCLUDED SPECIES: Physoctonus debilis (C.L. Koch, 1840); Physoctonus striatus, sp. nov.

DISTRIBUTION: Physoctonus is endemic to northeastern Brazilian, and has been recorded in the states of Bahía, Ceará, Paraíba, Pernambuco, and Piauí (fig. 9).

ECOLOGY: The two species of Physoctonus inhabit the semiarid Brazilian caatinga and cerrado (fig. 2D). These small, lapidicolous scorpions have been collected under stones and with UV light detection at night.

REMARKS: Physoctonus, created to accommodate Physoctonus physurus Mello-Leitão, 1934, was synonymized with Rhopalurus when Francke (1977 a) synonymized P. physurus with Rhopalurus debilis. Physoctonus was later revalidated by Lourenço (2002). Its validity was upheld by the analyses of Esposito et al. (in review), which consistently recovered the monophyly of its two species as distinct from the species of Rhopalurus (fig. 13), and the cytogenetic study of Ubinski et al. (2016) which identified a diploid chromosome number of 2n = 26 for R. debilis (table 2).