A new species of the genus Mesobuthus Vachon , 1950 ( Scorpiones , Buthidae ) from Xinjiang , China

A new species of the genus Mesobuthus Vachon, 1950 is described, based on specimens collected in the northern piedmont of the Tianshan Mountains, Xinjiang. It is characterized by a slender chela, general coloration yellow to pale brownish-yellow, elongate aculeus and 2–4 markedly large and moderately extroversive lobed granules of the ventrolateral carinae of metasoma segment V. With the description of this new species, the number of known Chinese species of Mesobuthus is raised to fi ve.


Introduction
Th e genus Mesobuthus Vachon, 1950 currently includes 12 species (Fet and Lowe 2000;Gantenbein et al. 2000;Lourenço et al. 2005;Kovařík 2007), and it is widespread in the Palearctic region, from Balkans to China and Korea Peninsula.It is distributed in diff erent habitats, but especially in the arid deserts, from Gobi to Central Asia and to Northwest China and Mongolia.Th e fi rst species of Mesobuthus described from China was Mesobuthus martensii martensii by Karsch (1879), originally described in the genus Buthus as Buthus martensii.After the description of M. martensii martensii two other species, Mesobuthus caucasicus przewalskii and Mesobuthus eupeus mongolicus were described by Birula (1897Birula ( , 1911)).Moreover, Birula (1904) also described a new subspecies, Mesobuthus martensii hainanensis, based on one specimen of unknown sex, and labeled from Hainan Island.Th is subspecies remains, however, of dubious validity mainly because it was never found again in the Island of Hainan or from adjacent areas, but also because no species of Mesobuthus was ever found inhabiting evergreen rain forest.Mesobuthus eupeus thersites and Mesobuthus caucasicus intermedius have also been recorded from China (Fet 1994;Fet and Lowe, 2000).More recently, Lourenço et al. (2005) described the fourth species of this genus from China, Mesobuthus songi, based on old preserved specimens from the northern piedmont of Himalayas, Xizang (Tibet).
In comparison with scorpion faunas in adjacent regions (e. g.Vachon 1958;Tikader and Bastawade 1983;Fet 1989), the diversity of scorpions in Xinjiang appear to be rather poor.Having in account that this region of China remained inaccessible during the past several decades and considering its very important surface, it is quite possible that this fauna has been largely underestimated.In fact, scorpion taxonomy and biogeography in China remains yet a considerably poorly known subject of study, and this until very recently (Zhu et al. 2004).All studies in Xinjiang were done by foreign experts (Birula, 1897(Birula, , 1904(Birula, , 1911(Birula, , 1917;;Schenkel, 1936).Since then, no other experts have been involved in the study of Xinjiang scorpions.As a part of a research project on the entire Chinese scorpion fauna, a research team is conducting fi eld work in Xinjiang.Among the scorpions found in the region, there are several specimens of Mesobuthus, which were collected in the northern piedmont of the Tianshan Mountains and correspond to a distinct new species.It represents the fi fth known species of this genus from China.

Material and methods
Specimens were examined and measured under a Leica M165c stereomicroscope with an ocular micrometer.Illustrations were produced using a Leica M165c stereomicroscope with a drawing tube.All measurements follow Stahnke (1970) and are given in millimetres (mm), except for the chela (Vachon, 1952).Trichobothrial notations follow Vachon (1974) and morphological terminology mostly follows Hjelle (1990).Specimens used in this taxonomic work come from the Museum of Hebei University, Baoding (MHBU) and the American Museum of Natural History, New York (AMNH).Diagnosis.Coloration.Basically brownish-yellow; all carinae and posterior edges of carapace and tergites with blackish-brown to black pigments; dorsal surfaces of segments I-IV on metasoma and each surface of segment V with irregular netlike dark pigments.Pedipalps: brownish-yellow; femur and patella with dark pigments, especially around carinae; manus with irregular netlike dark pigments; rows of granules on dentate margins of the fi ngers blackish-brown.Legs: pale yellow to yellow; tip of femur and base of patella with some dark spots.
Morphology.Total length 66-77 mm in females and 55-60 mm in males.Prosoma: anterior margin with a weak median concavity, not serrate; all carinae moderately strong, granular, and granules moderately developed; Mesosoma: Tergite: I to VI tricarinate; carinae on I weak, and carinae on II-VI moderately to strong, granular; the intercarinal surfaces relatively smooth, except for the segments I-III with sparse and fi ne granules; exterior surfaces coarsely granular.Pectinal teeth number 20-25 in females and 26-30 in males.Metasoma: Segments I-V with 10-8-8-8-5 complete carinae; median lateral carinae complete on segment I, only with sparse granules and covered 1/3 length of segment on II, and obsolete, remaining 1-3 granules at distal end on III; ventrolateral carinae on segment V strong, serrate, becoming stronger gradually from anterior to posterior; lateral surfaces smooth, dorsal with some fi ne granules and ventral with sparse large granules.Aculeus longer than a half of telson length.Pedipalps: Trichobothrial pattern: Orthobothriotaxic A-β (Vachon, 1974(Vachon, , 1975)).Dentate margins of movable and fi xed fi ngers with 12 and 11 oblique rows of granules respectively; outer accessory denticles becoming smaller from base to tip markedly, and obviously smaller than inner accessory denticles on the tip.Legs: Tarsus ventrally with two moderate to long longitudinal rows of setae.
Note.Although our fi eld works in Xinjiang are going along in past four years, and we got a large amount of specimens, we could not fi nd any evidence to support the distribution of Mesobuthus caucasicus intermedius in China.But here, we decide to refer to Fet and Lowe (2000) before our completing the investigations.
Morphology.Total length 68-78 mm in females and 50-68 mm in males.Prosoma: anterior margin with a weak median convexity, fi nely serrate; all carinae strong, granular and granules markedly biggish; Mesosoma: Tergite: I to VI tricarinate; all carinae strong, granular, except the median carina on I, weak; the intercarinal surfaces relatively smooth, except for the segments I-III with sparse and fi ne granules; exterior surfaces coarsely granular.Pectinal teeth number 15-19 in females and 19-23 in males.Metasoma: Segments I-V with 10-8-8-8-5 complete carinae; median lateral carinae complete on segment I, only with sparse granules and covered 1/2 length of segment on II and 1/3 on III; ventrolateral carinae strong, serrate, becoming stronger gradually from anterior to posterior; lateral and dorsal surfaces with some fi ne granules and ventral with sparse large granules.Aculeus about equal to a half of telson length.Pedipalps: Orthobothriotaxic A-β (Vachon, 1974(Vachon, , 1975)).Manus of chela relatively robust.Dentate margins of movable and fi xed fi ngers with 11 and 10 oblique rows of granules respectively; outer accessory denticles becoming smaller from base to tip, and smaller than inner accessory denticles on the tip.Legs: Tarsus ventrally with two moderate to long longitudinal rows of setae.
Diagnosis.Species of moderate size, with respect to the genus.General coloration yellow to pale brownish-yellow; ventral and lateral surfaces of metasoma segment V with inconspicuous variegated black pigment.Chela smooth without carinae, long and slender.Th e metasoma segments elongate; median lateral carinae complete on segment I, only with sparse granules and covered 1/2-2/3 length of segment on II and obsolete, remaining 1-2 granules at distal end on III; ventrolateral carinae of segment V strong, serrate, becoming strongly marked posteriorly and with 2-3 markedly large and extroversive lobed granules; aculeus markedly longer than a half of telson length.Dentate margins of movable and fi xed fi ngers with 12 and 11 oblique rows of granules.Pectinal tooth count 22-23 in females and 27-28 in male.Mesobuthus longichelus sp.n. is undoubtedly associated with Mesobuthus caucasicus intermedius and Mesobuthus caucasicus przewalskii, but it can be distinguished by above features, and especially by these three characters: the shape of chela, the median lateral carinae of segment II and III on metasoma, and the shape of ventrolateral carinae of segment V on metasoma.
Etymology.Th e specifi c name derives from the Latin "longi + chel", meaning long and chela, referring to the long and slender chela, especially the manus.
Description.Based on female holotype.
Morphology.Prosoma: anterior margin with a very weak median concavity; carinae moderately strong, granular and granules relatively minor; central median carinae directly connected with posterior median carinae and lateral median carinae by a row of sparse granules; posterior median carinae terminating distally in a small spinoid process which extends slightly beyond the posterior margin of the carapace; intercarinal surfaces smooth, except for the surfaces between central median carinae and posterior median carinae, which are globally, sparsely and fi nely granular; the extercarinal surfaces with sparse small granules; the surfaces between anterior median carinae and lateral eyes coarsely granular; furrows moderate.Median ocular tubercle slightly anterior to the centre of carapace; median eyes separated by almost 1.75 ocular diameters; three pairs of lateral eyes.
Mesosoma: Tergite: I to VI tricarinate; lateral carinae on I-VI moderate, granular; the median carina on I weakly, median carinae on II-VI moderate, granular; each carina on I-VI terminating distally in a small spinoid process which extends beyond the posterior margin of tergite, except the median carina on I; the intercarinal surfaces relatively smooth, except for the posterior margins with sparse and fi ne granules; exterior surfaces moderately to coarsely granular; VII pentacarinate; two pairs of lateral carinae moderate to strong; median carinae present on proximal half, moderate; the intercarinal surfaces smooth.Sternites: III-VII smooth; lateral margins slightly serrate; VII with four weakly marked carinae, granular.Pectines: moderately long; pectinal teeth 22-23 (see variation on table I).
Metasoma: Segments I with 10 complete carinae, segment II-IV with 8 complete carinae; all carinae moderately strong, granular, except the dorsal carinae, serrate; median lateral carinae complete on segment I, only with sparse granules and covered 1/2-2/3 length of segment on II and obsolete, remaining 1-2 granules at distal end on III.Intercarinae surfaces on segments I to IV smooth, except the surfaces between dorsal and dorsolateral carinae on segment I, which are weakly granular.Segment V pentacarinate; ventral carina moderate, granular; ventrolateral carinae strong, serrate, becoming strongly marked posteriorly and with 2-3 markedly large and extroversive lobed granules; dorsolateral carinae weakly developed, obsolete posteriorly; dorsal and lateral surfaces smooth, ventral surface with sparse large granules.Telson smooth dorsally and weakly granular ventrolaterally; aculeus long, markedly more than a half of telson length (see variation on table I).
Chelicerae: Dentition as defi ned by Vachon (1963) for the family Buthidae.Pedipalps: Trichobothrial pattern: Orthobothriotaxic A-β (Vachon, 1974(Vachon, , 1975)).Femur pentacarinate, moderately to strongly granular; ventrointernal carina with spinoid granules.Patella with seven carinae, very weakly to moderately granular.Intercarinal surfaces on both segments smooth.Chela smooth without carinae; long and slender (table I).Dentate margins of movable and fi xed fi ngers with 12 and 11 oblique rows of granules respectively; outer accessory denticles becoming smaller from base to tip, and smaller than inner accessory denticles on the tip.
Legs: Tarsus ventrally with two long longitudinal rows of setae; tibial spurs present on legs III and IV, moderately marked; pedal spurs present and moderately developed on all legs.
Ecology.Th e new species was found mainly in habitats composed of very arid and strongly desertifi ed grassland, under very big and oval rocks.Th is region is constituted by alluvial plains, and is located about 10 km north of the Tianshan Mountains.Th e area is quite droughty during the whole year, and even during summer.Th e vegetation is composed of scarcely shrubs, and is strongly xerophytic.