Angustopelta cribrorum Rathbun 1932, n. comb.
Creators: name: Ng, Peter K. L.
name: Castro, Peter
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chasmocarcinidae
Angustopelta
Angustopelta cribrorum

description: Angustopelta cribrorum (Rathbun, 1932) n. comb.
(Figs. 11 D–F; 24E; 31F; 41C‒F; 52E, F; 59E, I; 73F‒I; 101E)
Hephthopelta cribrorum Rathbun, 1932: 35 [type locality: Japan, Sagami Bay].— Sakai 1939: 575; 1976: 551, fig. 298 [Japan].—Ng et al. 2008: 76 [in list].
Hephthopelta criborum [sic]— Serène 1964a: 240 [in list], 241, 242 [in key]; 1968: 92 [in list].
Type material. Holotype male (13.6 × 14.9 mm) (USNM 46388), Japan, Sagami Bay, 14 mi. off Joka Shima Light, Albatross, stn 5086, 35°08’15”N, 139°22’E, 534 m, green mud, coarse black sand, 23.10.1906.
Other material examined. South China Sea. 1 male (9.9 × 11.6 mm) (ZRC 2015.214), off Pratas Is., stn CP4130, 20°17.971’N –15.914’N to 116°07.966’E– 116°07.987’E, 795–822 m, T.- Y. Chan coll., 02.05.2014; 1 female (10.8 × 12.5 mm) (ZRC 2015.296), southwest off Tungsha Islands, stn. CP4133, 20°04.51’N– 19°58.89’N to 116°22.367’E–116°24.28’E, 999–1070 m, sandy bottom with thin-stalked sponges, Zhongsha Expedition, T.-Y. Chan coll., 22.07.2015.
Diagnosis. Carapace (Figs. 11 D–F; 101E) subtrapezoidal, gently convex, front bilobed, with shallow median cleft; anterolateral margins arcuate, minutely granular with granules higher along lateral margins, without distinct large tubercles or teeth. Eye peduncle (Fig. 24 E) filling orbit, short, immobile; cornea reduced, with reduced pigmentation. Epistome (Fig. 24 E) broad, posterior margin with semicircular median lobe with deep median fissure, semicircular lateral margins. Third maxilliped (Fig. 31 F) merus subquadrate, ischium quadrate, slightly longer than merus. Proportionally long ambulatory legs (Fig. 11 D, E), folded P5 reaching front. Chelipeds (Figs. 11 E, F; 41C–F; 101E) subequal in length, heteromorphic; fingers of minor chela (Fig. 41 D, F) subcircular in crosssection, gently tapering to tip, scissor-like, cutting margins with distinct sharp teeth; closed fingers of major chela of males forming wide, circular gap. Inner margin of cheliped carpus with sharp tooth. Ventral surface of cheliped merus with 4 teeth along outer margin, large median tubercle on distal margin in holotype. Inner margin of carpi with long distal tooth (Fig. 11 D, E). Fused thoracic sternites 1, 2 (Fig. 52 E, F) semicircular, transversely narrow, long. Press-button for pleonal holding as small, short tubercle posterior to thoracic sternal suture 4/5 near edge of sterno-pleonal cavity (Fig. 59 I). Male pleon (Figs. 52 E, F; 59E) with proportionally short telson. G1 (Fig. 73 F‒H) stout, distal segment curved outwards, with short spinules, tuft of setae just before tip. G2 (Fig. 73 I) about 1/2 G1 length, straight, distal segment proportionally long. Female unknown.
Colour. The carapace and pereiopods are dirty white when cleaned in freshly collected specimens (Fig. 101 E).
Remarks. The illustration of the supposed USNM holotype given by Sakai (1976: fig. 298) is very schematic and does not correspond to the actual specimen (USNM 46388; Fig. 11 D). The front is rounded, not straight, and the carapace is nearly oval, not subtrapezoidal in the illustration. The only remaining cheliped, the left one, is drawn more accurately. The holotype is diagnosed in detail with ample figures here. Recent Taiwanese specimens collected from off Pratas Is. in the northern South China Sea agree very well with the type and we are confident they are conspecific.
Angustopelta cribrorum has a carapace that is very similar to A. robusta n. sp. and A. modesta n. sp., being subtrapezoidal and with the anterolateral margin entire or with only a small tubercle. In the case of A. cribrorum, no granule or tubercle is visible on the anterolateral margin at all in both specimens, although the margin appears to be uneven (Fig. 11 D‒F). While usually visible as a small tubercle in A. robusta n. sp. and A. modesta n. sp. (e.g., Fig. 13 F, H), however, it is also sometimes absent in these two species (e.g., Fig. 13 A, G) so this cannot be a good character. Compared to A. robusta n. sp., A. cribrorum has proportionately longer and more slender ambulatory legs (Fig. 11 D, E) (shorter and stouter in A. robusta n. sp.; Fig. 12 A, B); the lateral margins of male pleonites 3 and 4 are more rounded and convex (Fig. 59 E) (somites more acute and less convex in A. robusta n. sp.; Fig. 59 F); and most significantly, the basal part of the G1 is more truncate and the distal part is relatively more slender (Fig. 73 F‒H) (G1 with basal part less truncate and the distal part is relatively stouter in A. robusta n. sp.; Fig. 74 A‒D). The ambulatory legs of A. modesta n. sp. (Fig. 12 C‒G) are comparable to those of A. cribrorum (Fig. 11 D, E), but the sutures between male pleonites 3‒5 are still visible (Fig. 59 G, H) (absent in A. cribrorum; Fig. 59 E), and the basal part of the G1 is relatively more slender, with the distal part longer, more slender and distinctly curved (Fig. 74 F‒H) (G1 with basal part stouter and distal part shorter, stouter and gently curved in A. cribrorum; Fig. 73 F‒H).
Distribution. Western Pacific Ocean (Japan, South China Sea). Depth: 534– 822 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 57-59, DOI: 10.11646/zootaxa.4209.1.1, http://zenodo.org/record/272646