Stygochactas, Vignoli & Prendini, 2009

Vignoli, Valerio & Prendini, Lorenzo, 2009, Systematic Revision Of The Troglomorphic North American Scorpion Family Typhlochactidae (Scorpiones: Chactoidea), Bulletin of the American Museum of Natural History 2009 (326), pp. 1-94 : 46-52

Stygochactas , new genus

Type species Typhlochactas granulosus Sissom and Cokendolpher, 1998 [5 Stygochactas granulosus ( Sissom and Cokendolpher, 1998) ].

DIAGNOSIS: Stygochactas is the sister taxon of Typhlochactas (fig. 4). It may be separated from Typhlochactas and Sotanochactas on the basis of the following combination of characters. Size moderate to large, total length of adult estimated (from single pedipalp chela) to be 60–70 mm. Cheliceral fixed finger with four teeth (subdistal present); median and basal teeth fused into a bicusp. Cheliceral movable finger with four dorsal teeth (one subdistal present). Carapace, anterior margin, median projection (epistome) obsolete. Pedipalps moderately elongated, chela fingers slightly longer than manus. Pedipalp femur, ventroexternal carina and patella, internomedian carina absent. Pedipalp chela, dorsal secondary, digital, ventroexternal, ventromedian, and ventrointernal carinae distinct. Chela fixed and movable fingers, median denticle rows of each comprising seven oblique primary subrows; basal primary subrows similar in length to other subrows; terminal denticle of fixed finger considerably larger than preceding denticles, hooklike, fingertips interlocking unevenly when closed. Patella trichobothrium v 1 situated level with trichobothrium esb 1. Chela fixed finger, external trichobothria distributed across entire length of finger, with trichobothrium eb situated near base of finger; trichobothria it and ib situated near base of finger. Legs without prolateral pedal spurs. Basitarsi I and II, proventral surfaces without short row of closely aligned spinules subdistally. Telotarsi, ventral surface, with curved proximal row spinules; without ventromedian row of spinules. Tergite VII, dorsolateral carinae absent or vestigial. Metasomal segments I–IV, dorsosubmedian carinae obsolete; I–III, dorsolateral carinae distinct; I, median lateral carinae absent; I–V, ventrolateral carinae absent or obsolete; V, ventromedian carina absent.

INCLUDED TAXA: Monotypic genus: Stygochactas granulosus ( Sissom and Cokendolpher, 1998) .

DISTRIBUTION: Endemic to Mexico. Recorded from Veracruz.

Stygochactas granulosus ( Sissom and Cokendolpher, 1998) ( Figs. 1B , 4 , 5C , 6D , 8A , 9E, 9F , 10I–L , 12B , 20–22 ; table 7)

Typhlochactas granulosus Sissom and Cokendolpher, 1998: 285–290 , table 1, figs. 1–11.

Typhlochactas granulosus : Sissom, 2000b: 499; Soleglad and Fet, 2003a: fig. 13; 2003b: 30, 162; Vignoli and Kovařík, 2003: 131; Volschenk and Prendini, 2008: 236 (table 1).

TYPE MATERIAL: Mexico: Veracruz: Município Tlaquilpa: Holotype: 1 juv. ³ ( AMNH), Sótano de Poncho [18 ° 379N 97 ° 079W, 273 m], P. Sprouse, 22.III.1995.

DIAGNOSIS: As for genus.

DESCRIPTION: The following redescription supplements the original description of the holotype (fig. 20) by Sissom and Cokendolpher (1998).

Color: Chelicerae, carapace, legs, tergites, sternites, metasoma uniformly Cream (54); pedipalp chela Buff Yellow (53). Cheliceral teeth paler; pedipalp chela manus and denticle rows of fingers darker; ungues similar in color to telotarsi, but slightly darker distally (fig. 20).

Chelicerae: Manus, dorsal and ventral surfaces smooth; dorsal surface with four microsetae situated near base of fixed finger; movable finger with few microsetae. Fixed finger, dorsal margin with four teeth (distal, subdistal, median, and basal; fig. 5C); distal tooth largest, median and basal teeth equal, fused into bicusp. Movable finger, internal distal and external distal teeth opposable, internal distal tooth completely overlapping external distal tooth in dorsal view; dorsal margin with four teeth (internal distal, subdistal, median, and basal), internal distal tooth largest, subdistal and median teeth equal, smaller, basal tooth smallest; ventral surface with serrula along distal half of finger, comprising relatively large tines, partially covered by dense brush of macrosetae.

Carapace: Length similar to anterior width (table 7). Anterior margin sublinear, with small median projection (epistome) and six macrosetae (fig. 6D). Posterior margin sublinear; asetose. Median and lateral ocelli absent. Median longitudinal sulcus present, shallow; posterolateral sulci shallow; posteri- or transverse sulcus deep. Surface acarinate, uniformly finely granular, especially on posterolateral surfaces. Surface and margins with several microsetae.

Pedipalps: Pedipalps moderately elongated (figs. 21, 22). Femur, dorsoexternal, dorsointernal, ventrointernal, ventroexternal carinae obsolete, granular (fig. 22A). Dorsal, external, and internal surfaces with scattered granules; ventral surfaces smooth. Patella dorsoexternal carina distinct, granular; dorsoexternal, ventroexternal, and ventrointernal carinae obsolete; internomedian carina absent or vestigial, comprising at most one or two granules besides dorsal process; externomedian carinae absent (fig. 22B–D). Intercarinal surfaces less granular than femur; dorsal surfaces smooth; external surfaces with few larger granules distally; internal surface uniformly finely granular, with few larger granules proximally; ventral surfaces smooth. Chela manus slightly swollen, fingers longer than manus (fig. 21). Dorsal secondary, digital, ventroexternal, ventromedian, and ventrointernal carinae distinct, composed of similar, rounded granules; external secondary carina obsolete; other carinae absent. Manus, intercarinal surfaces smooth; internal surface with prominent, isolated granule near movable finger condyle and pair of prominent, isolated granules situated close together at base of fixed finger; fixed finger, proximal half granular dorsally. Manus and fingers covered by macrosetae; several extremely long macrosetae situated terminally on fingers. Fixed finger, median denticle row comprising seven oblique primary subrows of denticles, similar in length except for basal subrow, which is shorter (fig. 9E); internal denticles larger than external denticles; terminal denticle of fixed finger considerably larger than preceding denticles, hooklike, fingertips interlocking unevenly when closed. Movable finger, median denticle row comprising seven oblique primary subrows of denticles, terminal and proximal subrows shortest (fig. 9F); terminal denticle enlarged.

Trichobothria: Femur with three trichobothria (fig. 22A): one external (e), one dorsal (d), one internal (i). Patella with 19 trichobothria (fig. 22B–D), five petite (d 1, d 2, et 2, esb 2, eb 2), one accessory (em 3): two ventral (v 1, v 2); 14 external (et 1 –et 3, est, em 1 –em 3, esb 1, esb 2, eb 1 – eb 5); two dorsal (d 1, d 2); one internal (i). Chela with 26 trichobothria (fig. 21), seven petite (V 1, Et 4, Et 5, Esb, Db, esb , db): 16 on manus, four ventral (V 1 – V 4), 10 external (Et 1 – Et 5, Est, Esb, Eb 1 – Eb 3), two dorsal (Db, Dt); 10 on fixed finger, four external (et, est, esb , eb), four dorsal (dt, dst, dsb, db), two internal (it, ib).

Legs: Femur and patella II–IV, ventral surfaces, sparsely granular; basitarsi each with two rows of long macrosetae. Basitarsi I–IV without prolateral pedal spurs; I and II, proventral surface without spinules. Telotarsi, dorsomedian lobe with one microseta; ventral surface with curved row of spinules, proximally, and four or five submedian pairs of subspiniform macrosetae (fig. 10I–L); ungues long, curved, equal in length; dactyl short, robust.

Tergites: Pretergites, surfaces smooth. Posttergites, surfaces densely and finely granular, more so on VII, with scattered microsetae and pair of macrosetae submedially on posterior margins; I–VI, acarinate, VII, dorsosubmedian and dorsolateral carinae vestigial, reduced to few posterior granules (fig. 20A).

Sternum: Posterior width greater than length (fig. 8A); apex slightly rounded; lateral margins converging anteriorly; lateral lobes flat; posterior depression shallow. Surface with two pairs of macrosetae and several microsetae.

Genital operculum: Sclerites completely divided, strongly rounded posteriorly, each with single macroseta situated medially; genital papillae protruding distinctly beyond posterior edges (fig. 8A).

Pectines: Pectinal plate, surface with pair of macrosetae. Lamella comprising three segments (fig. 8A), demarcated by very faint sutures; surfaces with several macrosetae and numerous microsetae. Tooth count: 5/4; distal tooth larger, broader.

Sternites: Surfaces and margins smooth, acarinate (fig. 20B), with scattered microsetae; VII with several macrosetae. Respiratory spiracles (stigmata) small, round, situated posterolaterally.

Metasoma: Segments elongated, length greater than width (fig. 12B), progressively increasing in length, decreasing in width (table 7); segment V much longer than carapace. Dorsosubmedian carinae, segments I–IV, obsolete, granular, distal granules not noticeably larger than preceding granules (fig. 12B); V, absent. Dorsolateral and ventrolateral carinae, segment V, obsolete, granular, complete. Dorsolateral, median lateral, ventrolateral and ventrosubmedian carinae, segments I–IV, and ventromedian carina, segment V, absent. Dorsal intercarinal surfaces, segments I–IV, slightly concave; V, convex. Dorsal and ventral intercarinal surfaces sparsely granular, especially posteriorly; lateral intercarinal surfaces smooth. All segments with several macrosetae, especially on ventral surfaces.

Telson : Vesicle broad, elongated, flattened dorsally, rounded ventrally; anterodorsal lateral lobes absent (fig. 12B); surface smooth, with scattered long macrosetae. Aculeus short, weakly curved, arising gradually from vesicle.

Hemispermatophore: Adult male unknown.

Ontogenetic variation: The granulation and sclerotization of the chela are more pronounced in the adult than the juvenile.

Sexual dimorphism: Female unknown.

Geographical variation: Single complete specimen.

REMARKS: The movable finger of the dextral pedipalp chela of the holotype is detached. A large, sinistral pedipalp chela, also without a movable finger, was collected together with the holotype and placed in the same vial. According to Sissom and Cokendolpher (1998: 289) this chela ‘‘structurally resembles the chela of Alacran tartarus Francke, 1982 , known only from deep caves of the Sistema Huautla, Oaxaca … but until more material becomes available it will not be possible to draw comparisons with the Oaxacan specimens.’’ We compared the damaged chela with the types of A. tartarus and the holotype of S. granulosus and observed that, aside from its larger size, more pronounced granulation and sclerotization (all consistent with sexual maturity), the chela was otherwise identical to that of the holotype of S. granulosus . The proximal half of the fixed finger was granular dorsally, the median denticle row comprised seven oblique primary subrows, the basal subrow being the shortest, and there were six internal denticles. The chelal carination, though more pronounced, was consistent with the holotype of S. granulosus . Except for three trichobothria, which could not be observed due to damage to the specimen (V 1, Et 1, ib), the following 23 trichobothria were observed in the same positions as in the holotype of S. granulosus (fig. 18): 14 on manus, three ventral (V 3 – V 4), nine external (Et 2 – Et 5, Est, Esb, Eb 1 – Eb 3), two dorsal (Db, Dt); nine on fixed finger, four external (et, est, esb , eb), four dorsal (dt, dst, dsb, db), one internal (it). Six of these trichobothria were petite, based on the smaller diameter of their areolae: Et 4, Et 5, Esb, Db, esb , db. The presence of seven primary subrows on the median denticle row of the fixed finger, six petite trichobothria, the absence of three accessory trichobothria, and other differences in trichobothrial positions rule out the possibility that the chela is conspecific with A. tartarus , or indeed that it is congeneric. Based on the overwhelming similarity of the chela to that of the holotype of S. granulosus , together with their collection from nearby one another in the same cave, we conclude that they are conspecific, that the chela belongs to an adult of the species and that the holotype is a juvenile. The discovery is significant because the length of the chela (at least 11 mm, as the tip of the finger is missing) is comparable to that of A. tartarus (12–14 mm), implying that the adult of S. granulosus may be similar in size (adult A. tartarus measure 60–70 mm in length), and hence that this would represent the second large-bodied species in the family, albeit from a much shallower cave (273 m). The finding also calls into question whether some species of Typhlochactas , known only from single specimens and/or females (notably T. cavicola and T. reddelli ), are adult and, if not, what size the adults might reach. In this regard, it is noteworthy that the second-largest typhlochactine specimen known, the holotype of T. sissomi , is subadult. Its total length is 0.3 mm greater than the adult male holotype of T. rhodesi and 0.9 mm greater than the adult male paratype of S. elliotti (tables 4, 5).

DISTRIBUTION: Known only from the type locality, Sótano de Poncho (Veracruz, México) (fig. 1B).

ECOLOGY: This troglobitic species was taken from a vertical cave, 95 m long and 73 m deep, with a small entrance ( Sissom and Cokendolpher, 1998). The holotype was collected on the talus slope at the base of the entrance drop and the single pedipalp chela collected nearby.

ADDITIONAL MATERIAL: Mexico: Veracruz: Município Tlaquilpa: 1 ad., pedipalp chela only (AMNH), Sótano de Poncho [18 ° 379N 97 ° 079W, 273 m], P. Sprouse, 22.III.1995.

Figures

Fig. 1. Map of Mexico, showing the known localities of Typhlochactidae Mitchell, 1971. A. Known localities of Alacraninae, new subfamily: Type locality of Alacran tartarus Francke, 1982, on the Huautla Plateau, Oaxaca (1); Te Cimutaá Cave, Oaxaca, a new record for the genus possibly representing a new species of Alacran Francke, 1982 (2). B. Type localities of Typhlochactinae Mitchell, 1971: Sotanochactas elliotti (Mitchell, 1971), El Sótano de Yerbaniz, San Luis Potosí (1); Stygochactas granulosus (Sissom and Cokendolpher, 1998), Sótano de Poncho, Veracruz (2); Typhlochactas cavicola Francke, 1986, Cueva del Vandalismo, Tamaulipas (3); Typhlochactas mitchelli Sissom, 1988, Cerro Ocote, Oaxaca (4); Typhlochactas reddelli Mitchell, 1968, La Cueva del Ojo de Agua de Tlilapan, Veracruz (5); Typhlochactas rhodesi Mitchell, 1968, La Cueva de la Mina, Tamaulipas (6); Typhlochactas sissomi Francke et al., 2009, Cañada de La Joya, Queretaro (7); Typhlochactas sylvestris Mitchell and Peck, 1977, 25 km S Valle Nacional, Oaxaca (8).

Fig. 4. Single most parsimonious tree (312 steps, CI: 57, RI: 56) obtained by cladistic analysis of 142 morphological characters (appendix 1) scored for nine taxa in the family Typhlochactidae Mitchell, 1971, and three outgroup taxa under weighting regimes that maximized fit and minimized length (Prendini et al., 2009). Unambiguous synapomorphies are indicated with bars. Solid bars indicate uniquely derived apomorphic states, whereas empty bars indicate parallel derivations of apomorphic states. The number above each bar gives the character number, the number below gives the character state.

Fig. 5. Typhlochactidae Mitchell, 1971, chelicerae, dorsal aspect. A. Alacran tartarus Francke, 1982, paratype ³ (AMNH). B. Sotanochactas elliotti (Mitchell, 1971), paratype ³ (WDS). C. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH). D. Typhlochactas cavicola Francke, 1986, holotype ♀ (AMNH). E. Typhlochactas mitchelli Sissom, 1988, holotype ³ (AMNH). F. Typhlochactas reddelli Mitchell, 1968, holotype ♀ (AMNH). G. Typhlochactas rhodesi Mitchell, 1968, holotype ♀ (AMNH). H. Typhlochactas sissomi Francke et al., 2009, subad. ³ holotype (IBUNAM), dextral chelicera. I. Typhlochactas sylvestris Mitchell and Peck, 1977, holotype ♀ (AMNH), sinistral chelicera. Scales: A 5 1 mm; B–H 5 0.1 mm.

Fig. 6. Typhlochactidae Mitchell, 1971, carapace, dorsal aspect. A. Alacran tartarus Francke, 1982, paratype ³ (AMNH). B. Alacran tartarus Francke, 1982, ♀ (WDS). C. Sotanochactas elliotti (Mitchell, 1971), paratype ³ (WDS). D. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH). Scales: A, B 5 1 mm; C, D 5 0.5 mm.

Fig. 8. Typhlochactidae Mitchell, 1971, sternum, genital operculum and pectines, ventral aspect. A. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH). B. Typhlochactas mitchelli Sissom, 1988, holotype ³ (AMNH). C. Typhlochactas cavicola Francke, 1986, holotype ♀ (AMNH). D. Typhlochactas sylvestris Mitchell and Peck, 1977, holotype ♀ (AMNH). Scales 5 0.5 mm.

Fig. 9. Typhlochactidae Mitchell, 1971, dextral pedipalp chela fixed (left) and movable (right) fingers, dentition patterns. A, B. Alacran tartarus Francke, 1982. C, D. Sotanochactas elliotti (Mitchell, 1971). E, F. Stygochactas granulosus (Sissom and Cokendolpher, 1998). G, H. Typhlochactas cavicola Francke, 1986. I, J. Typhlochactas mitchelli Sissom, 1988. K, L. Typhlochactas reddelli Mitchell, 1968. M, N. Typhlochactas rhodesi Mitchell, 1968. O, P. Typhlochactas sissomi Francke et al., 2009. Q, R. Typhlochactas sylvestris Mitchell and Peck, 1977.

Fig. 10. Typhlochactidae Mitchell, 1971, sinistral legs I–IV, basitarsi and telotarsi, retrolateral aspect. A–D. Alacran tartarus Francke, 1982, ♀ (WDS). E–H. Sotanochactas elliotti (Mitchell, 1971), paratype ³ (WDS). I–L. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH). Scales: A 5 0.1 mm; B, C 5 0.5 mm.

Fig. 12. Typhlochactinae Mitchell, 1971, metasoma and telson, lateral aspect. A. Sotanochactas elliotti (Mitchell, 1971), paratype ³ (WDS). B. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH). C. Typhlochactas cavicola Francke, 1986, holotype ♀ (AMNH). D. Typhlochactas mitchelli Sissom, 1988, holotype ³ (AMNH). E. Typhlochactas reddelli Mitchell, 1968, holotype ♀ (AMNH), segments IV, V and telson only. F. Typhlochactas rhodesi Mitchell, 1971, holotype ♀ (AMNH). G. Typhlochactas sylvestris Mitchell and Peck, 1977, holotype ♀ (AMNH). Scales 5 1 mm.

Fig. 20. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH), habitus. A. Dorsal aspect. B. Ventral aspect. Scale 5 1 mm.

Fig. 21. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH), sinistral pedipalp chela showing carinae and distribution of trichobothria. A. Dorsal aspect. B. External aspect. C. Ventral aspect. Scale 5 0.5 mm.

Fig. 22. Stygochactas granulosus (Sissom and Cokendolpher, 1998), juv. ³ holotype (AMNH), sinistral pedipalp femur (A) and patella (B–D) showing carinae and distribution of trichobothria. A, B. Dorsal aspect. C. External aspect. D. Ventral aspect. Scales 5 0.5 mm.