Hephthopelta occidentalis Ng & Castro, 2016, n. sp.
Creators: name: Ng, Peter K. L.
name: Castro, Peter
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chasmocarcinidae
Hephthopelta
Hephthopelta occidentalis

description: Hephthopelta occidentalis n. sp.
(Figs. 10 I, J; 24B; 31C; 40G, H; 52B, C; 59C; 72)
Type material. Holotype male (6.1 × 6.6 mm, with sacculinid) (MNHN-IU-2010-1031), Madagascar, along Mahajamba Bay, MIRIKI, stn CP3249, 14°48’S, 47°00’E, 620‒637 m.
Paratypes: 1 male (4.7 × 4.9 mm) (ZRC 2015.247, ex-MNHN-IU-2010-1284), between Majunga and Cape Saint-André, MIRIKI, stn CP3279, 15°22’S, 45°57’E, 780‒1020 m, 12.07.2009.
Diagnosis. Carapace (Fig. 10 I, J) subtrapezoidal, globose, slightly wider than long; front bilobed, with shallow to well-defined median cleft; anterolateral margins arcuate, minutely granular, without distinct lobes or teeth. Orbits (Fig. 24 B) short, eye peduncle filling orbit, short, immobile; cornea reduced, with prominent spot of black pigment. Posterior margin of epistome (Fig. 24 B) with broadly triangular median lobe, deep median fissure, lateral margins semicircular. Third maxilliped (Fig. 31 C) merus ovate, ischium slightly elongated, slightly longer than merus. Proportionally long ambulatory legs (Fig. 10 I), folded P5 merus almost reaching anterior margin; P5 merus 0.8 cl. Meri of P2, P3 with short teeth, meri of other ambulatory legs with microscopic granules, unarmed.
Chelipeds (Figs. 10 I, J; 40G, H) subequal in length, slightly dissimilar in female, heteromorphic in males; fingers of minor chela (Fig. 40 H) flattened laterally, broad throughout most of length, shear-like, cutting margins with low, broad teeth. Ventral surface of cheliped merus with 3 teeth (additional smaller teeth or large tubercle) on outer margin, inner margin unarmed. Inner margin of carpi with long distal tooth (Fig. 10 I, J). Fused thoracic sternites 1, 2 (Fig. 52 B) transversely narrow, high; fused thoracic sternites 3, 4 (Fig. 52 B); transversely narrow. Pleon of holotype parasitized by sacculinid (Fig. 52 C). G1 (Fig. 72 A–C) stout, distal part straight with spinules. G2 (Fig. 72 D) longer than G1, straight, slender, distal segment directed inwards, almost as long as basal segment. Female unknown.
Etymology. The epithet occidentalis refers to geographical distribution of the new species, which is so far restricted to the Western Indian Ocean.
Remarks. Although only two specimens of H. occidentalis n. sp. are available, they possess several characters that separate them from H. lugubris. Hephthopelta occidentalis can be separated by the posterior margin of the epistome being broadly triangular (Fig. 24 B) (posterior margin of epistome is truncate in H. lugubris, Fig. 24 A), the ambulatory meri are relatively longer (Fig. 10 I) (meri are relatively shorter in specimens of H. lugubris of comparable size; Fig. 10 D–H), the ischium and merus of the third maxilliped are proportionately longer (Fig. 31 C) (ischium and merus proportionately shorter and more quadrate in specimens of H. lugubris of comparable size; Fig. 31 A, B), and the cornea of the eye has a prominent spot of black pigment (Fig. 24 B) (cornea with only a faint trace of black pigmentation in H. lugubris, Fig. 24 A).
The G1 of H. occidentalis appears to be relatively shorter and stouter (Fig. 72 A) than that of H. lugubris (Fig. 71 A, B, F, G, J). A smaller specimen of H. lugubris from Fiji (6.3 × 6.5 mm, MNHN-IU-2013-9028), however, also has a relatively short G1 (Fig. 71 K, L), suggesting the distal part elongates in larger specimens. While the tip of the G 1 in H. occidentalis is directed obliquely laterally (Fig. 72 A–C), however, that of H. lugubris is still gently curved upwards (Fig. 71 K, L). In any case, the G1 appears to vary slightly in H. lugubris, a smaller specimen from Solomon Is. (7.3 × 7.8 mm, MNHN-IU-2013-9037) has a more rounded carapace but with a G 1 in which the distal part is elongated and gently curved upwards, but has the basal part relatively more slender than that of larger males (Fig. 71 J versus Fig. 71 F, G).
Distribution. Only known from Madagascar. Depth: 620‒1020 m.
description: Published as part of Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), pp. 1-182 in Zootaxa 4209 (1) on pages 53-55, DOI: 10.11646/zootaxa.4209.1.1, http://zenodo.org/record/272646