Singhaplax orientalis ( Tesch, 1918 ) 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 : 715-716

Singhaplax orientalis ( Tesch, 1918) n. comb.

Ommatocarcinus orientalis Tesch, 1918: 186 , pl. 10, figs 2, 2 a- 2 e [ Indonesia]. — Barnard 1950: 286 [discussion]. — Serène 1968: 89 [in list]. — Takeda & Miyake 1969b: 174 [discussion]. — Guinot 1971: 1082 [in list].

TYPE MATERIAL. — Siboga , stn 260, ♂ holotype, cl 2.3 mm, cw 4.5 mm ( ZMA De 103.007).

TYPE LOCALITY. — Indonesia, Kai Islands, 05°36.5’S, 132°55.2’E, 90 m.

MATERIAL EXAMINED. — Indonesia. Kai Is, Siboga Expedition , stn 260, 05°36.5’S, 132°55.2’E, 90 m, 16-18.XII.1899, ♂ holotype, cl 2.3 mm, cw 4.5 mm ( ZMA De 103.007).

DISTRIBUTION. — Known only from Indonesia (Kai Is). Depth: 90 m.

REMARKS

Ommatocarcinus orientalis Tesch, 1918 is known from only one specimen, the male holotype. It was collected by the Siboga Expedition from the Kai Is, Indonesia ( Tesch 1918: 186). The long G2 clearly shown in Tesch’s illustration ( Tesch 1918: pl. 10, fig. 2 e, as Ommatocarcinus orientalis ), the length of the eye peduncles (much shorter than Ommatocarcinus ), the general morphology of the carapace and pereopods, and the small overall size clearly show that Tesch’s species does not belong to Ommatocarcinus but to Singhaplax .

Tesch unfortunately did not include the G1 (nor the G2, even if it was illustrated) in the extensive description of his new species. The holotype (ZMA De 103.007) still has the intact G1 even if the abdomen was detached. The G1 is slender and nearly straight, with a scarcely wider proximal part (peduncle). The tip is pointed and acute, and there is a row of small, obtuse denticles along the inner margin of the distal part. The G2, as shown by Tesch (1918: 186, pl. 10, fig. 2e, as O. orientalis ), is long and slender and has one terminal spinule.

The morphologies of the G1 and G2 plus other characters (narrow male abdomen, absence of a tooth on the median portion of the cheliped meri) demonstrate that S. orientalis , even if known from only one specimen, is distinct from the other four species of Singhaplax ( S. dichotoma n. sp., S. platypoda n. sp., S. rhamphe n. sp., and S. styrax n. sp.) plus a similar small-size species ( Microgoneplax pelecis n. sp.) that are being described from apparently similar habitats in the Kai Is. These six species of Singhaplax and Microgoneplax n. gen. appear to be sympatric, although it is possible that there are dif- ferences in their particular microhabitats (sediment size, relative position in the sediment) or behaviours (feeding habits, activity patterns, association with other species).

Barnard (1950: 286) commented that the small holotype of S. orientalis “appears to be a juvenile”, but his assumption was most probably wrong. The G1 and G2 of the holotype are clearly fully formed.