Geosesarma raj, Schubart & Ng, 2014

Schubart, Christoph D. & Ng, Peter K. L., 2014, Two new species of land-dwelling crabs of the genus Geosesarma De Man, 1892 (Crustacea: Brachyura: Thoracotremata: Sesarmidae) from Bintan Island, Indonesia, Raffles Bulletin of Zoology 62, pp. 615-619 : 616-618

publication ID	https://doi.org/ 10.5281/zenodo.4504166
publication LSID	lsid:zoobank.org:pub:924CD2C9-3007-4321-81E2-0237EE1359BA
persistent identifier	https://treatment.plazi.org/id/C89B65EA-D107-464B-9325-23A53624BE3B
taxon LSID	lsid:zoobank.org:act:C89B65EA-D107-464B-9325-23A53624BE3B
treatment provided by	Carolina
scientific name	Geosesarma raj
status	sp. nov.

Treatment

Geosesarma raj View in CoL , new species

( Figs. 1B, D View Fig , 2B, D View Fig , 3B, D, F View Fig , J–M, 4)

Material examined. Holotype – male (11.8 × 10.9 mm) ( MZB Cru 3814, ex ZRC 2007.0676 View Materials ), Indonesia: Riau Archipelago, northern Bintan Island , coll. G. Subaraj, 18 October 2007 . Paratypes – 1 female (11.8 × 10.7 mm) ( ZRC 2007.0677 View Materials ), Indonesia: Riau Archipelago, Bintan Island , in tree hole, coll. G. Subaraj, 21 October 2007 ; 1 male (10.0 × 9.7 mm) ( ZRC 2007.0675 View Materials ), Indonesia: Riau Archipelago, Bintan Island: Gunong (= Mount ) Bintan , above lower waterfalls (attacked by ants), coll. G. Subaraj, 23 June 2007 ; 1 male (9.4 × 9.0 mm), 2 females (7.3 × 6.8 mm, 6.4 × 6.2 mm) ( ZRC 1996.133 View Materials – 135 View Materials ), Gunung Bintan Besar , coll. Y. H. Lee, 19 February 1996 .

Diagnosis. Carapace almost squarish, not distinctly wider than long, lateral margins almost parallel ( Fig. 1B, D View Fig ); dorsal surfaces evenly covered with numerous granules and striae; H-shaped median depression deep; postfrontal cristae prominent, margins sharp; exorbital tooth triangular, curving obliquely, with additional low tooth behind it ( Figs. 1B View Fig , 2B View Fig ). Exopod of third maxilliped relatively stout, without flagellum ( Fig. 3B View Fig ). Male chelae with long fingers, numerous granules on palm (dorsally and ventrally) and proximal part of dactylus; dorsal margin of dactylus with 8 or 9 sharp granules on proximal two-thirds ( Fig. 2D View Fig ). Ambulatory legs with relatively slender meri, with sharp subdistal spine on dorsal margin, surface almost smooth; propodus elongate ( Figs. 1B View Fig , 3D View Fig ). Male abdomen relatively narrow; telson longer than broad, with rounded tip ( Fig. 3F View Fig ). G1 relatively stout, distal chitinous part elongate, tapering; subdistal part broad ( Fig. 3 View Fig J–M).

Colour. The carapace of this species is reddish brown in life, with the chelipeds bright orange ( Fig. 4 View Fig ).

Etymology. The species is named after G. Subaraj (“Raj” to all his friends), the collector. The specific epithet, raj , is used as a noun in apposition.

Remarks. The quadrate carapace, the absence of a flagellum on the exopod of the third maxilliped, and the stout G1, which has a prominent, chitinised, beak-like structure on the distal end with the subdistal part broad, ally Geosesarma raj , new species, with species like G. malayanum Ng & Lim, 1986 , G. scandens Ng, 1986 , G. tiomanicum Ng, 1986 , from Peninsular Malaysia, and G. katibas Ng, 1995 , from Sarawak, East Malaysia.

Geosesarma raj , new species, can be distinguished from G. scandens (type locality: Fraser’s Hill) by its relatively longer third maxilliped merus ( Fig. 3B View Fig ) (shorter in G. scandens ; cf. Ng, 1988: fig. 62C) and the upward-directed (at a more gradual angle) chitinised distal part of the G1 ( Fig. 3 View Fig J–M) (chitinised distal part directed at a steeper angle in G. scandens ; cf. Ng, 1988: fig. 62D, E). Geosesarma raj , new species, can be separated from G. malayanum (type locality: Johor) by its more rugose dorsal surfaces of the carapace ( Fig. 1B, D View Fig ) (relatively less rugose in G. malayanum ; cf. Ng & Lim, 1987: pl. 1; Ng, 1988: fig. 63A); relatively shorter ambulatory legs ( Fig. 1B View Fig ) (longer in G. malayanum ; cf. Ng & Lim, 1987: pl. 1; Ng, 1988: fig. 63A); and the G1 which is slightly less stout, with the chitinised distal part relatively longer ( Fig. 3 View Fig J–M) (stouter with the chitinised distal part relatively short in G. malayanum ; cf. Ng & Lim, 1987: fig. 1; Ng, 1988: fig. 63D–G). The new species differs from G. tiomanicum (type locality: Pulau Tioman) by its relatively longer third maxilliped merus ( Fig. 3B View Fig ) (relatively shorter merus in G. tiomanicum ; cf. Ng, 1988: fig. 61C), the tip of the chitinised distal part of the G1 being subtruncate ( Fig. 3 View Fig J–M) (tip sharp; cf. Ng, 1988: fig. 61D, E). From G. katibas (type locality: Sarawak), G. raj , new species, can be distinguished by its relatively longer third maxilliped merus ( Fig. 3B View Fig ) (shorter in G. katibas ; cf. Ng, 1995: fig. 11B); the dorsal margin of the dactylus of the male major chela having fewer (8 or 9) and less developed granules ( Fig. 2B View Fig ) (11 distinct granules; cf. Ng, 1995: fig. 11C, D); and the G1 being proportionately longer and less stout ( Fig. 3 View Fig J–M) (relatively shorter and stouter in G. katibas ; cf. Ng, 1995: fig. 12A–E).

In many other parts of Peninsular Malaysia and Singapore, there is one lowland species living in swampy areas, often in burrows, and another that occurs in higher altitudes, under rocks in fast-flowing streams. In Johor and Singapore, for example, G. peraccae occurs in lowland freshwater swamps while G. nemesis and G. malayanum prefer high-elevation areas with fast-flowing streams (see Ng & Lim, 1987; Ng, 1988, 1990). The same situation appears to be present in Pulau Bintan, with G. bintan as the lowland species while G. raj occurs in more montane habitats, but not necessarily in streams.