Camatopsis thula n. sp.

(Figs. 7 C‒F; 23G; 30D; 39E, F; 51D; 58D; 67M‒O; 86D; 90D; 100H)

Camatopsis rubida — Yokoya 1933: 202 [Japan].— Sakai 1936: 193, pl. 55, fig. 4; 1939: 576, pl. 68, fig. 4; 1965: 173, pl. 85, fig. 4; 1976: 552, pl. 195, fig. 4 [Japan].— Takeda 1973a: 13; 1973b: 55; 1997: 247 [Japan].— Fang 1991: 352, 355, fig. 4 [map] [Taiwan].— Muraoka 1998: 47 [Japan].—Ng et al. 2001: 34 [in list] [Taiwan].— Hsueh & Huang 2002: 113, fig. 2A [Taiwan].— Jiang 2008: 770 [in list] [Taiwan].— Komai et al. 2012: 149, fig. 6. Not Camatopsis rubida Alcock & Anderson, 1899 .

Type material. Holotype male (8.9 × 9.3 mm) (ZRC 1999.0662), Taiwan, Ilan County, Tashi Fishing Port.

Paratypes: 1 male (9.0 × 10.5 mm) (ZRC 2009.0347), Taiwan, Ilan County, Tahsi Fishing Port, 26.08.2000; 1 female (7.3 × 8.2 mm) (ZRC 2009.0348), Ilan County, Tahsi Fishing Port, 01.12.1999; 2 females (ZRC 1999.0749), S.H. Wu coll., 02.10.1990; 1 ovigerous female (10.1 × 10.7 mm) (ZRC 1999.752), P.K.L. Ng et al. coll., 15.05.1995; 1 female (ZRC 1998.420), Ilan County, Tashi Fishing Port, S.H. Wu coll., 05.1997; 1 female (8.7 × 9.7 mm) (ZRC 2015.185), Ilan County, Tashi Fishing Port, P. - H. Ho coll., 09.01.1999; 1 male (9.9 × 10.8 mm), 1 female (10.2 × 11.1 mm) (ZRC 1999.0751), Ilan County, Tashi Fishing Port, P.K.L. Ng & K. Lim coll., 05.1999; 1 male (10.2 × 11.1 mm) (ZRC 2001.2215), TAIWAN 2001, stn CP77, 24°54.18’N, 122°02.46’E, 360 m.

Other material examined. Japan. 1 male, 1 female (SMF) [dried], unknown location, T. Sakai collection. — 1 male, 2 females (NSMT-Cr 12101), Suruga Bay, South Senoumi Bank, stn DG96-6, 157– 159 m, 14.11.1996.

Taiwan. 1 male, J.W. Lim coll., 0 5.01.1999 (ZRC 1999.0750).

Diagnosis. Carapace (Figs. 7 C–F; 100H) subtrapezoidal, 1.0‒1.2 wider than long; front bilobed, with shallow or deep median cleft; anterolateral margins arcuate, carapace minutely granular with granules higher along lateral margins, without distinct lobes or teeth. Eye peduncle (Fig. 23 G) filling orbit, short, slightly mobile; cornea reduced, with reduced pigmentation. Epistome (Fig. 23 G), semicircular median lobe with deep median fissure, semicircular lateral margins. Third maxilliped (Fig. 30 D) merus quadrate, outer margin convex, ischium subquadrate, about same length as merus. Proportionally short ambulatory legs (Fig. 7 E, F); P5 merus 0.6 cl. Chelipeds (Figs. 7 E–F; 39E, F; 100H) subequal in length, slightly dissimilar in females, heteromorphic in males. Major chela of males (Fig. 39 E) with thick propodus, cutting margins with few sharp teeth (arched, proximal, toothless gap in large males). Minor chela of both sexes (Fig. 39 F) with cutting margin of pollex having 2 long, sharp teeth that overlap dactylus when closed. Inner margin of cheliped carpus smooth. Fused thoracic sternites 1, 2 (Fig. 51 D) triangular, proportionally narrow, short. Male pleon (Figs. 51 D; 58D) with proportionally short telson G1 (Fig. 67 M, N) stout, distal segment slightly curved, distal segment curved inwards towards sternum at approximately right angles, slightly twisted, with short to long spinules. G2 (Fig. 67 O) about 3/4 G1 length, straight, slender, short distal segment. Female pleon (Fig. 86 D) with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity of female (Fig. 90 D) moderately deep, vulvae far apart from each other.

Colour. The carapace and pereiopods are light brown in life (Fig. 100 H).

Etymology. The name is derived from Thoule, Greek for “farthest north”, in reference to the species showing the northernmost extension of all of the species of Camatopsis .

Remarks. Camatopsis thula n. sp. is characterised by possessing the shortest and stoutest ambulatory meri in the genus, and by having a G 1 in which the distal part is sharply bent inwards (Fig. 67 M, N).

Fang (1991) found C. thula (as C. rubida) to be the dominant species of brachyuran crab in soft sediments in the Taiwan Strait. Biomass of C. thula and other crab species was higher in finer sediments.

Distribution. Japan and Taiwan. Depth: 65‒660 m (Sakai 1976).