Singhaplax dichotoma, Castro, 2007

Castro, Peter, 2007, A reappraisal of the family Goneplacidae MacLeay, 1838 (Crustacea, Decapoda, Brachyura) and revision of the subfamily Goneplacinae, with the description of 10 new genera and 18 new species, Zoosystema 29 (4), pp. 609-774 : 714-715

Singhaplax dichotoma n. sp.

( Fig. 35 )

TYPE MATERIAL. — KARUBAR, stn DW 29, ♂ holotype, cl 4.0 mm, cw 6.1 mm ( MNHN-B 30069). — MUS- ORSTOM 1, stn CP 25, ♂ paratype, cl 3.2 mm, cw 5.0 mm ( MNHN-B 30070). — MUSORSTOM 2, stn DR 34, ♂ paratype, cl 3.8 mm, cw 5.9 mm ( MNHN-B 10286).

TYPE LOCALITY. — Indonesia, Kai Islands, 05°36’S, 132°56’E, 181- 184 m.

MATERIAL EXAMINED. — Philippine Islands. South China Sea, MUSORSTOM 1, stn CP 25, 14°03’N, 120°20’E, 191-200 m, 22.III.1976, 1 ♂ paratype, cl 3.2 mm, cw 5.0 mm ( MNHN-B 30070).

MUSORSTOM 2, stn DR 34, 13°27.0’N, 121°12.0’E, 167- 155 m, 24.XI.1980, 1 ♂ paratype, cl 3.8 mm, cw 5.9 mm ( MNHN-B 10286).

Indonesia. Kai Is, KARUBAR, stn DW 29, 05°36’S, 132°56’E, 181-184 m, 26.X.1991, ♂ holotype, cl 4.0 mm, cw 6.1 mm ( MNHN-B 30069).

ETYMOLOGY. — From dichotomus, Greek for “cut in two”, in reference to the bilobed tip of the G1 characteristic of the species.

DISTRIBUTION. — Philippine Is and Indonesia (Kai Is). Depth: 155- 200 m.

DESCRIPTION

Carapace ( Fig. 35A ) transversely rectangular, much wider than long (1.5 as wide as long in holotype). Carapace convex, without clear indication of regions. Front straight to slightly sinuous. Slight notch between front, inner edge of supraorbital border. Supraorbital borders broad, conspicuously sinuous, smooth, with long simple setae. Suborbital borders conspicuously sinuous, with short, acute granules; short, wide inner tooth not visible dorsally. Long, slender, acute tooth on outer orbital angle; tooth medially placed on carapace. Lateral borders beyond outer orbital teeth slightly curved, no anterolateral teeth.

Subhepatic, pterygostomial regions, with low, round tubercles.

Eye peduncles ( Fig. 35A ) long (equal to front width), cornea elongated, spherical distal margin.

Chelipeds (P1) unequal (female unknown); fingers slender, dactylus curved, slightly shorter than propodus, with blunt teeth; no dark colour on fingers; inner (ventral) margin of propodus smooth. Broad tooth on inner (ventral), proximal margin of carpus; outer (dorsal) margin of merus with low tubercles, long simple setae. Ambulatory legs (P2-P5) long, slender, unarmed, varying number of long, plumose setae; dactyli long, slender, each with 2 carinae along each side; length of P5 merus 0.8 cl.

Male abdomen wide (see abdomen of S. platypoda n. sp., Fig. 36A ), with 6 freely-movable somites plus telson; telson slightly longer than wide. Somite 3 covers most of space between P5 coxae; somite 2 only slightly narrower than somite 3, leaving small portion of thoracic sternite 8 visible. G1 ( Fig. 35B ) long, relatively stout, slightly wider basal part, straight distal part with large denticles; wide, truncated tip with 2 divergent, nearly triangular processes. G2 ( Fig. 35C ) slender, long, nearly equal or slightly longer than G1, curved flagellum slightly shorter than proximal part (peduncle), tip with terminal spinule.

Female unknown.

REMARKS

The new species is closest to Singhaplax ockelmanni ( Serène, 1971) . The G1 is bilobed in both species but the apical processes are different. They are large and beak-like in S. ockelmanni ( Serène & Umali 1972: figs 86, 87; Serène & Soh 1976: fig. 15B, B’) but they are much smaller in the new species ( Fig. 35B ). Specimens from the Philippine Is and Indonesia identified here as S. ockelmanni are of the same size range of the type material of S. dichotoma n. sp., which precludes the possibility that the new species represents the pre-adult of S. ockelmanni . Another difference is the G2, with a pointed tip in S. ockelmanni ( Serène & Umali 1972: fig. 88; Serène & Soh 1976: fig. 15C) but with a conspicuous terminal spinule in the new species ( Fig. 35C ). The male telson is different from that of other species of Singhaplax , except S. platypoda n. sp. and S. styrax n. sp., by being slightly longer than wide.

Figures

FIG. 35. — Singhaplax dichotoma n. sp.,♂ holotype,cl 4.0 mm, cw 6.1 mm, Kai Is, Indonesia,KARUBAR,stn DW 29 (MNHN-B 30069): A, dorsal surface of the carapace; B, left G1, ventral view; C, right G2, ventral view. Scale bars: A, 5 mm; B, C, 1 mm.

FIG. 36. — Singhaplax platypoda n. sp., ♂ holotype, cl 2.8 mm,cw 5.1 mm,Kai Is, Indonesia,KARUBAR,stn DW 22 (MNHN-B 29215): A, abdomen; B, right G1, ventral view; C, right G2, ventral view. Scale bars: A, 2 mm; B, C, 1 mm.