Megachactops, Ochoa & Rojas-Runjaic & Pinto-da-Rocha & Prendini, 2013

Ochoa, José A., Rojas-Runjaic, Fernando J. M., Pinto-da-Rocha, Ricardo & Prendini, Lorenzo, 2013, Systematic Revision Of The Neotropical Scorpion Genus Chactopsis Kraepelin, 1912 (Chactoidea: Chactidae), With Descriptions Of Two New Genera And Four New Species, Bulletin of the American Museum of Natural History 2013 (378), pp. 1-121 : 108-111

Megachactops , n. gen.

TYPE SPECIES: Megachactops kuemoi , n. sp.

ETYMOLOGY: The generic name reflects the larger size and close phylogenetic relationship with Chactopsis , and is masculine in gender.

DIAGNOSIS: Megachactops , n. gen., is most closely related to Chactopsis and Chactopsoides , n. gen. The three genera exhibit the following similarities, by means of which they may be separated from other chactid genera: cheliceral movable finger with one subdistal tooth on ventral margin; pedipalp patella with seven ventral trichobothria, chela manus with three ventral and seven external trichobothria, and fixed finger with 16 trichobothria; chela manus with nine carinae; fixed and movable fingers with multiple primary rows of denticles; metasomal segments with DL, ML, and VL carinae consistently present, and with porous areas situated posteriorly at LIM position.

Megachactops , n. gen., may be separated from Chactopsis and Chactopsoides , n. gen., as follows. The carapace exhibits distinct lateral median carinae, and its anterior margin possesses a conspicuous median notch in Megachactops , n. gen. (fig. 64), whereas the carapace is acarinate or with obsolete carinae and its anterior margin possesses a moderate to shallow median notch in Chactopsis and Chactopsoides , n. gen. (figs. 10, 11, 45). The pedipalp patellar DM carinae are present and the DPP prominent in Megachactops , n. gen. (figs. 70B, 74B), whereas the DM carinae are absent and the DPP present but weakly developed in Chactopsis and Chactopsoides , n. gen. Pedipalp patellar trichobothria v 6 and v 7 are aligned with v 1 – v 5 and situated close to the VE carina in Megachactops , n. gen. (figs. 70D, 74D), whereas v 6 and v 7 are situated submedially and out of alignment with v 1 – v 5, which are situated close to the VE carina, in Chactopsis and Chactopsoides , n. gen. Pedipalp chela trichobothrium db is situated medially on the fixed finger, and V 3 is situated in the distal third of the manus, closer to V 1 than to V 4 in Megachactops , n. gen., whereas db is situated in the proximal third of the fixed finger, and V 3 is situated medially on the manus, equidistant between V 1 and V 4, in Chactopsis and Chactopsoides , n. gen. The VSM carinae of metasomal segment IV are partial and the VM carina present (well developed or vestigial) medially in Megachactops , n. gen. (fig. 66, 68), whereas the VSM carinae are complete and the VM carina absent in Chactopsis and Chactopsoides , n. gen. (figs. 18, 19, 47). The ML carinae of metasomal segment V occupy less than half the length of the segment in Megachactops , n. gen., but more than half its length in Chactopsis and Chactopsoides , n. gen. The hemispermatophore of the three genera differs as follows. The apex is short and subtriangular, the lobe region well developed, occupying a third of the hemispermatophore length, with two lobes, the ental lobe elongated, the median lobe auriculate and almost apapillose, and the dorsal apophysis absent in Megachactops , n. gen. (figs. 72, 76), whereas the apex is elongat- ed, the lobe region reduced to one-fifth of the hemispermatophore length, the dorsal apophysis present, and the median lobe usually papillose in Chactopsis and Chactopsoides , n. gen.; the ental lobe is small in Chactopsis or absent in Chactopsoides , n. gen.

DESCRIPTION: The following general description outlines characters shared by both species of Megachactops , n. gen.

Total length: Scorpions of medium size, ranging in total length from 57–65 mm.

Coloration: The coloration in the two species is brownish with dark spots.

Chelicerae: Manus, dorsoexternal surfaces sparsely setose; ventral and internal surfaces densely setose. Fixed finger, dorsal margin with four teeth (distal, subdistal, median, and basal), median and basal teeth fused into a bicusp. Movable finger, dorsal margin with five teeth (distal, two subdistal, median, and basal); ventral margin with two teeth (distal, subdistal); dorsal distal tooth smaller than ventral distal tooth; ventral surface with short serrula.

Carapace: Anterior margin with deep median notch (fig. 64A–D). Posterior margin sublinear. Surfaces finely and densely granular ( M. coriaceo , n. comb., fig. 64A, B) or coarsely granular with nongranular surfaces punctate ( M. kuemoi , n. sp., fig. 64C, D); covered with scattered microsetae; anteromedian carinae well developed, granular; posteromedian carinae obsolete. Ocular tubercle well developed, situated slightly anteromedially; median ocelli well developed. Four pairs of lateral ocelli; anterolateral and median lateral pairs similar in size, approximately half the size of median ocelli; posterolateral pair smaller, approximately one-quarter the size of anterolateral and median lateral ocelli; dorsomedian pair greatly reduced, approximately one-quarter the size of posterolateral ocelli. Anteromedian longitudinal sulcus broad, well developed; postocular sulcus deep; posteromedian longitudinal, posterolateral, and posterior transverse sulci well developed; sulcus shallow.

Pedipalps: Patella, DM carina present. Chela manus narrow and cylindrical, with elongated fingers; nine carinae (D, SD, DS, DMA, DI, E, IM, VE, and VI) present, finely or moderately granular on manus. Fixed finger carinae moderately developed, granular; dentition very complex with multiple primary rows, median denticle row continuous, complete, flanked by nine or 10 internal and external denticles in distal twothirds; and numerous accessory denticles arranged in five (three internal and two external) rows.

Trichobothria: Femur with three trichobothria (figs. 70A, 74A): one external (e), one dorsal (d), one internal (i). Patella with 33 trichobothria (figs. 70B–D, 74B–D): two dorsal (d 1, d 2); seven ventral (v 1 –v 7), aligned and situated close to VE carina; 23 external (et 1 –et 5, est 1 –est 5, em 1 –em 3, esb 1 –esb 4, eb 1 – eb 6); one internal (i). Chela with 26 trichobothria (figs. 71, 75): 10 situated on manus, three ventral (V 1, V 3, V 4), V 3 situated in distal third of manus, closer to V 1 than to V 4, seven external (Et 1 – Et 3, Est, Esb, Eb 1, Eb 2); 16 situated on fixed finger, seven external (et 1 – et 3, est, em, esb, eb), six dorsal (dt, dst, dm 1, dm 2, dsb, db), db situated slightly distal to or in same axis as esb, three internal (it, ist, ib), ist situated approximately medially on fixed finger, isb absent.

Legs: Prolateral surfaces usually granular, retrolateral surfaces smooth. Tibial spurs absent. Pro- and retrolateral pedal spurs present. Basitarsi setose, each with dorsal and ventral rows of small brushlike spinules. Telotarsi setose, each with ventromedian row of elongated spinules, flanked by two paired rows of setae (pro- and retroventral and pro- and retrolateral); ungues well developed, curved, equal in length.

Sternum: Shape subpentagonal with two lateral lobes, and lateral margins converging anteriorly; posterior width greater than length; posterior depression deep (fig. 65).

Pectines: Pectinal plate, anterior margin with conspicuous median notch, lateral margins converging posteriorly (more so in ³). Pectines each comprising four lamellae, proximal and marginal lamellae larger, subdistal and distal lamellae smaller; fulcra absent (fig. 65). Tooth count, nine or 10.

Sternites: III–VI each with pair of small, oval spiracles, situated mediolaterally; surfaces finely and sparsely granular ( M. coriaceo , n. comb.), or smooth and punctate ( M. kuemoi , n. sp.). Sternite VII, VL carinae absent or obsolete, surfaces granular ( M. coriaceo , n. comb.) or smooth ( M. kuemoi , n. sp.).

Metasoma: Metasomal segments I–V, intercarinal surfaces coarsely and densely granular ( M. coriaceo , n. comb.) or smooth and punctate ( M. kuemoi , n. sp.); DL and VL carinae complete, granular; DSM and LSM carinae, vestigial or obsolete; DL carinae converging distally on segments I–III, subparallel on IV; ML carinae complete on segments I–IV, restricted to anterior half of V; LIM carinae less developed, complete only on segment I; porous areas, usually forming raised mounds, present posteriorly in place of LIM carinae on segments II–IV; VSM carinae discontinuous on segments III and IV, well developed ( M. coriaceo , n. comb.) or obsolete ( M. kuemoi , n. sp.); VM carinae restricted to anterior half of segments III and IV (vestigial in M. kuemoi , n. sp.), complete on V.

Telson: Vesicle slightly elongated. Aculeus short, gently curved (fig. 69).

Hemispermatophore: Lamina weakly sclerotized distally, lobe region and pedicel strongly sclerotized (figs. 72, 76); apex, subtriangular, and tapering distally; flagellum short; ental margin of apex with shallow proximal fold; articular flexure present; slight basal constriction, forming elongated pedicel, broadly fused with lobe region. Trunk well developed, tortuous medially; proximal part forming sheath-shaped base; distal part concave on ventral surface; foot well developed. Lobe region well developed, occupying approximately one-third the length of hemispermatophore, with two lobes (ental and median lobes); ental lobe elongated, terminating in strongly sclerotized apophysis; median lobe well developed, auriculate, extended ventrally, forming internobasal reflexion of sperm duct, almost apapillose; median trough conspicuous; dorsal apophysis absent.

INCLUDED TAXA: Two species, Megachactops coriaceo ( González-Sponga, 1991) , n. comb., and Megachactops kuemoi , n. sp.

DISTRIBUTION: The genus Megachactops , n. gen., is endemic to the state of Amazonas, Venezuela (fig. 2).

HABITAT: Both known species of Megachactops , n. gen., inhabit primary rainforest.