Isometrus tamhini Sulakhe & Dandekar & Padhye & Bastawade 2020, sp. n.

Isometrus tamhini sp. n.

(Figures 1–14, 36, 40, 46, 50, 54, 58, Tables 1a, e, 2–6)

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TYPE LOCALITY AND TYPE REPOSITORY. India, Maharashtra State, Pune District, Tamhini, Dongarwadi, 18.48°N 73.41°E, 638 m a. s. l.; BNHS.

TYPE MATERIAL. India, Maharashtra State, Pune District, Tamhini, Dongarwadi, 18.48°N 73.41°E, 638 m a. s. l., 1♂ (holotype, BNHS SC 155), 27 October 2018, 1♂ (paratype, INHER-73), 30 October 2018, 1♂ (paratype INHER-92), 2♀ (paratypes INHER-91 and INHER-94), 27 October 2018, 1♀ (paratype BNHS SC 156), 1♀ (paratype INHER-78), 23 October 2018. All specimens collected by S. Sulakhe, R. Yenpure, C. Risbud & M. Ketkar.

ETYMOLOGY. The species epithet is a noun in apposition indicating the Tamhini Village located in the Pune District, northern Western Ghats, the type locality of the new species. Suggested common name: Tamhini Tree Scorpion.

DESCRIPTION. (♂ holotype, measurements in Table 1a)

Coloration (Figs. 1, 2, 8, 9). Body and appendages yellowish brown and variegated with blackish brown stripes and spots; metasomal segment V and pedipalp fingers dark brownish. Ventral portion of the body uniformly yellow and posterior one-third portion of sternite V light yellowish to whitish. Basal segments of chelicera dorsally yellowish with blackish reticulation ending anteriorly into brownish transverse patch; Ventral surface of chelicera yellowish; fingers of chelicera dark brown. Telson blackish brown.

Carapace (Figs. 6, 36, 40). Surface densely and coarsely granular, almost entirely except few areas on lateral and posterior median portion. Carapace without carinae, except for a pair of conspicuous median supra-ocular carinae; with coarse granular texture. A pair of median eyes situated anteriorly in the ratio 1:2.2 (ratio of median eyes to anterior margin and median eyes to posterior margin). Anterolateral ocular tubercle granular, with three pairs of sub-contiguous lateral ocelli and two micro-ocelli situated behind the lateral ocelli. Median longitudinal furrow throughout the length of carapace. Anterior margin with shallow emargination coarsely granulated with conspicuous median notch. Lateral margins finely and densely crenulated below the lateral ocelli. Posterior margin almost entirely smooth, except for the latero-posterior portion.

Chelicerae. Characteristic of the family Buthidae. Basal segments and movable fingers with short and firm setae on the basal and ventral surfaces.

Pedipalp (Figs. 11–14). Femur with 5 carinae (dorsal exterior, dorsal interior, exterior median, interior median and exterior ventral). Exterior median carina with few granules more prominent, robust and triangularly tuberculate. All remaining carinae are evenly crenulated. Intercarinal space more granular on dorsal surface. Ventral surface almost smooth except few closely set granules on proximal portions. Patella with 7 distinct carinae (dorsal median, dorsal interior, dorsal exterior, exterior median, ventral exterior, interior median and ventral interior). Dorsal exterior, dorsal interior and dorsal median weakly granular. Dorsal interior supported with an additional short carina on anterior sub-dorsal portion. Interior median strongly tuberculated with few sub-denticulate granules. Exterior median, ventral exterior and ventral interior carinae smooth and obsolete. Intercarinal space weakly and finely granular. Manus without carinae and finely and sparsely granular. Fixed fingers with 2 smooth and obsolete carina (dorsal exterior and dorsal interior). Fixed and movable finger armed with 5 rows of linear dentition. Trichobothrial pattern typical for the genus.

Legs. Femur and patellae carinated. All carinae granular. Tibiae 3 and 4 without tibial spur. All legs with a pair of pedal spurs. Tarsomere covered with long delicate setae arranged in parallel rows on ventral side. Tarsomere I with a tuft of short, stout blackish setae. Tarsomere II compressed laterally. Dorsal margin of each leg ending into a pointed projection and ventrally provided with paired row of short, pointed, anteriorly directed, closely placed setae. Tarsomere II armed with a pair of sharply pointed curved claws and a soft, triangular and blunt basal claw.

Genital operculum (Figs. 3, 10). Wider than long, elliptical, separated, with a pair of short male genital papillae.

Pectines (Figs. 3, 10). Basal piece rectangular, deeply notched on anterior median margin. Posterior margin of basal piece slightly curved; smooth on surface with a parallel wide subbasal piece along the posterior margin. Surface provided with pairs of short, red setae. Pectines 4.5 times longer than width, marginal lamella of 3 digits and median lamella of 6 digits, external margin armed with a row of stout short red setae and few setae on surface. Fulcra number 15, roughly triangular each armed with few short red setae, placed in between adjacent pectinal teeth. Teeth number 16, strong and stout.

Mesosoma (Figs. 1–3, 6–9). Tergites I–VI sparsely and finely granular and with a granular median carina. Posterior and lateral margins granular. Tergite I with short median carina. Tergite VII narrow posteriorly, granular, provided with 2 pairs of lateral granular carinae, inners up to pre-tergal portion while external pair runs diverging laterally up to two-thirds portion and end abruptly. A broad median carina limited to anterior one-third of median portion. Sternites III – VI almost entirely smooth with a pair of spiracles; with very finely granular on posterior margins, other margins smooth, each tergite with different numbers of setae on surface and posterior margins. Sternite V with extended, convex, exceptionally smooth posterior median margin. Sternite VII smooth on posterior margin while finely crenulated to serrated on lateral margins; with 2 pairs of granular carinae; median carinae restricted to posterior two-thirds portion; lateral carinae present in the middle portion.

Metasoma (Figs. 1–2, 6–9). All segments longer than wide; basal segment two times longer than wide. Segment I with 5 pairs of carinae (dorsals, dorsolaterals, laterals, ventrolaterals and ventrals) well developed and granular, ending posteriorly in a sub-triangular blunt and weakly pointed tubercle. Intercarinal space weakly and finely granular, anterior margin granular. Segments II and III provided with 4 pairs of carinae (dorsal, dorsolateral, ventrolaterals and ventrals). Laterals granular and marked on posterior one-third portion of II and III segments. Intercarinal portion irregularly granular, dorsolateral and dorsal carinae posteriorly ending in to subtringular tubercles. Segment IV with 4 pairs of granular carinae (dorsal, dorsolateral, ventrolaterals and ventrals). Dorsals ending into subtringular tubercles. Intercarinal space less irregularly granular. Segment V with 7 carinae (dorsal, dorsolateral and ventrolateral pairs and single ventral); dorsal carinae weakly, sparsely and obsoletely granular. Dorsolaterals present throughout. Laterals totally absent. Ventrolaterals and single ventral median carinae granular and ending posteriorly into weakly granular anal rim. Intercarinal space irregularly and weakly granular than segments I–IV.

Telson (Figs. 4–5, 54).Vesicle elongated, smooth on dorsal surface. Lateral surface demarcated with granular ridge. Ventral median carina strongly granular ending into triangular, subaculear tooth, armed with a pair of minute denticles on inner margin. Ventral portion with 2 pairs of sparsely and finely granular carinae. Intercarinal space weakly and finely granular. Aculeus with strong acute angle between subaculear tooth and base of aculeus. Subaculear tooth more pointed and external margin along the ventral median carina almost straight with the vesicle.

SEXUAL DIMORPHISM. Male genital operculum partially exposed on posterior portion, from which a pair of small genital papillae is seen. In females, the genital operculum is separated with a median suture covering the female genital orifice (Figs. 3, 10).

AFFINITIES. Isometrus tamhini sp. n. is distinguished from its congeners based on the following set of characters:

1) Surface of carapace densely and coarsely granular as opposed to densely and finely granular in I. amboli sp. n., granular throughout but obsolete in I. maculatus, as opposed to sparsely granular with some areas without granules in I. thurstoni (Figs. 36–39). 2) External margin of subaculear tooth of telson along the ventral median carina, almost straight with the vesicle (Fig. 4). 3) Pedipalp length more than 5 times the carapace length in males as opposed to less than or equal to 5 times in males of I. thurstoni, I. amboli sp. n.,and I. maculatus (Table 1e). 4) Anterior margin of carapace with shallow emargination as opposed to anterior margin of carapace with deep emargination in I. thurstoni (Figs. 56–59). 5) Telson depth to telson length ratio is equal to or more than four times in males as opposed to less than four times in I. amboli sp. n. and I. thurstoni (Table 1e). 6) Telson aculeus less elongated in males (telson length 3 times or more than 3 times telson aculeus length) as opposed to telson aculeus more elongated (telson length always less than 3 times telson aculeus length) in males of I. amboli sp. n. and I. thurstoni (Table 1e, Figs. 52–54). 7) Ventral median carina on vesicle strongly granular as opposed to very weakly granular in I. thurstoni (Fig. 5). 8) Pectine length less than 5 times pectine width as opposed to pectine length greater than 5 times pectine width in I. maculatus (Table 1e).

DISTRIBUTION, HABITAT AND ECOLOGY. The new species is currently known only from the type locality. In our primary surveys, the specimens were found on tall trees in the semievergreen forests of Tamhini and Dongarwadi. All the specimens were found on large trees with rough bark having ridges, at a height of 2 to 4 meters (Figs. 15–16, 34–35).