Chinommatia cavimanus ( Rathbun, 1914 )

Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), Zootaxa 4209 (1), pp. 1-182 : 64-65

Chinommatia cavimanus ( Rathbun, 1914) n. comb.

( Figs. 14 A‒E; 25A; 32A; 42J, K; 43A, B; 44A, B, E, F; 53A, B; 60A; 75A‒D; 87D; 91D)

Chasmocarcinus cavimanus Rathbun, 1914: 149 [type localilty: Philippines].— Estampador 1959: 90 [in list] [Philippines]. Hephthopelta cavimanus — Serène 1964a: 240 [in list], 241, 243 [in key]; 1968: 92 [in list].— Zarenkov 1972: 238, fig. 1–3 [Vietnam].

Hephthopelta littoralis — Chen 1998: 298, fig. 22. Not Hephthopelta littoralis Tesch, 1918 . Hephthopelta cavimana —Ng et al. 2008: 76 [in list].

Type material. Holotype male (11.4 × 13.9 mm) ( USNM 46413 ), Philippines, Tanon Strait, east coast of Negros, Pescador I., 0 9o 56’30”N, 123o15’E, 549 m.

Other material examined. 6 males, 8 females, Philippines, type locality ( USNM 46412 ).—PANGLAO 2004 : 1 male (9.6 × 11.9 mm), 2 females (6.3 × 7.7 mm, 7.0 × 8.7 mm) ( ZRC 2015.223 ), Bohol I., Cortes , stn T25, 09°41.1’N, 123°49.3'E, 160–210 m, 24.06.2004 ; 2 females (4.5 × 6.0 mm, 9.2 × 11.2 mm), Bohol I., Cortes , stn T26, 09°43.3’N, 123°48.8'E, 123‒135 m, 24.06.2004 ( ZRC 2015.224 ). — AURORA 2007: 2 females (7.6 × 9.1 mm, 7.8 × 9.1 mm) ( ZRC 2015.225 ) [photographed] , 1 female (6.5 × 7.9 mm) (MNHN-IU-2014-12804, ex ZRC 2015.226), stn CP2655, 16°03’N, 121°54’E, 189 m, 20.05.2007 20.05.2007; 1 male (10.4 × 12.3 mm), 1 female (7.4 × 8.6 mm), 1 damaged female (ZRC 2015.227), stn CP2715, 14°31.50’N‒14°33.09’N to 121°42.14’E‒121°42.05’E, 244‒249 m, 29.05.2007; 3 males (8.1 × 10.2 mm, 9.0 × 11.2 mm, 10.1 × 12.2 mm), 1 female (7.6 × 9.0 mm) [photographed] (ZRC 2015.228), stn CP2716, 14°32.14’N‒14°30.41’N to 121°40.80’E‒121°41.16’E, 298‒356 m, 29.05.2007; 1 male (9.2 × 11.0 mm) (QM), 2 males (6.0 × 7.2 mm, 10.7 × 12.9 mm), 3 females (7.6 × 9.2 mm, 8.2 × 9.4 mm, 8.4 × 10.1 mm) (ZRC 2015.229), stn CP2717, 14°29.96’N‒14°28.94’N to 121°41.67’E‒121°43.13’E, 311‒362 m, 29.05.2007, 29.05.2007; 2 males (5.7 × 7.0 mm, 8.6 × 10.1 mm), 1 female (7.3 × 8.7 mm) (ZRC 2015.230), stn CP2720, 14°25.30’N‒14°26.63’N to 121°47.70’E‒121°46.68’E, 256‒301 m, 29.05.2007; 1 male (7.6 × 9.3 mm) (MNHN-IU-2014-12805, ex ZRC 2015.231), stn CP2721, 14°24.03’N‒14°26.26’N to 121°46.83’E‒121°47.56’E, 340‒360 m, 29.05.2007; 1 female (9.0 × 10.3 mm) (ZRC 2015.232), stn CP2722, 14°24.45’N‒14°25.80’N to 121°47.90’E‒121°46.19’E, 291‒338 m, 29.05.2007; 1 male (5.4 × 6.7 mm), 1 female (6.8 × 8.2 mm) (ZRC 2015.233), stn CP2723, 14°25.30’N‒14°23.27’N to 121°48.93’E‒121°50.45’E, 147‒156 m, 29.05.2007; 1 male (9.7 × 11.5 mm) (ZRC 2015.234) [photographed], stn CP2741, 16°02.67’N–16°02.93’N to 121°55.32’E‒121°53.72’E, 194‒203 m, 0 1.06.2007.

South China Sea. 1 male (6.1 × 7.3 mm) (IOCAS-MBM166773) [photographs examined], station SSBV 26-20 , Nansha Is., 10°04′N 115°55′E, 127 m, 31.07.1988.

Indonesia. 1 male (MNHN-IU-2013-9051), Makassar Strait , CORINDON 2, stn CH 276, 01°54.6’S, 119°13.8’, 456– 395 m, 0 8.11.1980.

Diagnosis. Carapace ( Fig. 14 A‒F) subtrapezoidal, convex, slightly tomentose in small individuals, 1.2 wider than long; front bilobed, with shallow to well-defined median cleft; anterolateral margins arcuate, minutely granular, anterolateral row of low tubercles ( Fig. 14 E, F), slightly high tubercle as part of row of low tubercles in some small specimens. Posterior margin of epistome ( Fig. 25 A) with narrowly rectangular median lobe with deep median fissure, semicircular lateral margins. Eye peduncle ( Fig. 25 A) filling orbit, long, slender, mobile; cornea not reduced, pigmented. Third maxillipeds ( Fig. 32 A) not filling buccal cavern when closed; merus subovate, outer margin convex, slightly elevated anteriorly, anteroexternal angle auriculiform; ischium slightly rectangular, about same length as merus. Chelipeds ( Figs. 14 A‒D; 43A, B; 44A, B) subequal in length, slightly dissimilar in female, heteromorphic in males; fingers of minor chela ( Fig. 43 A) subcircular in cross-section, gently tapering to tip, scissor-like, cutting margins with distinct, often sharp teeth; cutting margins of major chela of males with broad, blunt, pointed teeth in both sexes, largest most proximal on upper, lower cutting margin ( Fig. 43 A); propodus of minor chela of male ( Fig. 44 A, B) with large, swollen, elongated tooth on the inner margin anterior to large hollow, flat area, opposing flattened area on ventral surface of merus (tooth much smaller in female minor cheliped). Ventral surface of cheliped merus with row of tubercles, low sharp teeth in large individuals, along outer margin in both sexes ( Fig. 42 J, K). Inner margin of carpus with short distal tooth, short proximal part rounded (Fig. A‒E). Inner margin of basis-ischium of adult major cheliped gently granuliform ( Fig. 14 B). Adult ambulatory legs relatively long ( Figs. 14 A‒D; 44E, F). P5 dactylus distinctly upcurved (Fig, 14B), merus 0.7‒0.9 cl; meri of P2, P3 with small spinules or sharp granules along posterior margin, meri of other ambulatory legs with microscopic granules, unarmed. Fused thoracic sternites 1, 2 ( Fig. 53 A, B) semicircular, distinctly broad, short; fused sternites 3, 4 ( Figs. 53 A, B; 87D; 91D) broad. Male pleon ( Fig. 53 A, B; 60A) lateral margins of somite 6 nearly straight, fused somites 3–5 concave; telson proportionally long; postero-lateral regions as in rest of somite, not particularly swollen. Sterno-pleonal cavity deep, press-button for pleonal holding as short tubercle at center of sternal somite 5 near edge of sterno-pleonal cavity. Male thoracic sternite 8 long, rectangular; “supplementary plate” long subovate; structures tightly appressed with most of penis concealed (e.g., Fig. 60 C). G1 ( Fig. 75 A‒C) with slender basal part, gradually tapering along slightly curved distal part to tip, with short spinules. G2 ( Fig. 75 D) about 3/4 G1 length, slightly curved, distal segment proportionally long. Female telson proportionally long ( Fig. 87 D). Sterno-pleonal cavity of female ( Fig. 91 D) deep, vulvae relatively close together, located on outer margins of cavity close to suture 5/6.

Remarks. The ventral surface of the propodus of the small chela of both sexes is hollowed as a flat depression, with a large, compressed tooth on the inner, distal margin in the propodus in the case of males. As noted by Rathbun (1914: 150), this tooth fits in a concavity on the inner margin of the ventral surface of the merus when flexed.

Specimens identified and figured by Chen (1998: 298, fig. 22) as “ Hephthopelta littoralis ” are clearly C. cavimanus ; photographs of her specimens in IOCAS confirm this ( Fig. 14 E).

The name of the species remains as “ cavimanus ” regardless of the gender of the genus. This is because when Rathbun (1914) established “ Chasmocarcinus cavimanus ”, she did not give any indication if the name was to be used as a noun or adjective. Article 31.2.2 of the Code ( ICZN 1999) states that “Where the author of a speciesgroup name did not indicate whether he or she regarded it as a noun or as an adjective, and where it may be regarded as either and the evidence of usage is not decisive, it is to be treated as a noun in apposition to the name of its genus”. As such the spelling of the name “ cavimanus ” stays unchanged.

Distribution. Western Pacific Ocean ( Philippines to Indonesia). Depth: 123‒ 549 m.