Typhlocarcinops yui Ng & Ho, 2003

Ng, Peter K. L. & Rahayu, Dwi Listyo, 2020, A synopsis of Typhlocarcinops Rathbun, 1909 (Crustacea: Decapoda: Brachyura: Pilumnidae), with descriptions of nine new species from the Indo-West Pacific, Zootaxa 4788 (1), pp. 1-100 : 37-40

Typhlocarcinops yui Ng & Ho, 2003

( Figs. 31 , 32 , 40J )

Typhlocarcinops yui Ng & Ho, 2003: 172 , figs. 1C, 3; Ng et al. 2008: 144.

Material examined. 1 male (10.7 × 8.1 mm) ( SMF 37555), 30 m, Japan, coll. T. Sakai, no date .

Diagnosis. Carapace ( Figs. 31A , 32A ) about 1.3–1.4 times broader than long, surface pitted, glabrous medially, regions not indicated, H-shaped gastro-cardiac grooves slightly indicated; anterolateral margin arcuate, lined with tiny granules and sparse setae, entirely, or with shallow fissures separated 3 slightly indicated broad lobes. Front entire ( Fig. 31B, C ) appears gently sinuous when viewed dorsally with median part slightly depressed; no trace of lateral lobules. Orbit ( Figs. 31B, C , 32A ) short, bulbous ocular peduncles filling orbit, immovable, cornea small, well pigmented. Epistome ( Fig. 31C ) relatively broad, broadly triangular median lobe with median suture. Antennal peduncles relatively long. Third maxilliped ( Fig. 32B, H ) with merus squarish, outer and inner margins straight, ischium subovate, slightly broader, much longer than merus, inner margin slightly shorter than outer margin, lower margin slightly oblique; exopod relatively stout, tip reaching to just before distal edge of merus, inner margin with distinct tooth. Chelipeds unequal in males ( Figs. 31A, F, G , 32D ), outer surface of fingers of chela smooth, with shallow longitudinal sulcus and scattered tubercles proximally on dactylus; fixed finger with longitudinal ridge, surface of palm, carpus and merus granular, carpus with slight triangular protuberance on inner angle ( Figs. 31H , 32C ); P2−P5 ( Fig. 31A, E ) proportionally short, fringe by sparse long setae on dorsal and ventral margins; merus of P5 not reaching front when folded. Fused thoracic sternites 1, 2 broadly triangular ( Fig. 31D ), proportionally narrow; thoracic sternites 3, 4 with suture discernible. Male pleon ( Figs. 31D , 32E, I ) relatively narrow, telson relatively short, about 1.5 times as long as somite 6, subtriangular with rounded distal margin. G1 ( Figs. 32F, G , J–M, 40J) slender, upper half about as long as lower half, distal part elongate, curved at right angle, with pointed tip.

Remarks. Typhlocarcinops yui was described from one male (6.5 × 4.7 mm) collected from 128–132 m depths in the Taiwan Straits, between the main island of Taiwan and Penghu Islands (23º16.00’N 119º52.80’E). The species is well characterized and figured, its most distinctive feature being its G1, with the distal part elongate and curved at right angles ( Ng & Ho 2003: 174). The present specimen from Japan agrees well in all features. The G1 shape of T. yui superficially resembles that of T. denticarpes , but in T. denticarpes , the upper half is shorter than the lower half (versus upper and lower halves about the same length in T. yui ), and the distal part is relatively long, sinuous with pointed tip ( Fig. 40 G‒I) (versus the distal part is distinctly elongate, curved at right angle, and with pointed tip in T. yui , Fig. 40J ).

Type locality. Taiwan .

Distribution. Taiwan and Japan. Soft sediments at 30–132 m depth.

Figures

FIGURE 31. Typhlocarcinops yui Ng & Ho, 2003, male (10.7 × 8.1 mm) (SMF 37555), Japan. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, anterior thoracic sternum and pleon; E, right fourth ambulatory leg; F, outer view of left chela; G, outer view of right chela; H, right carpus of cheliped.

FIGURE 32. Typhlocarcinops yui Ng & Ho, 2003.A–F, holotype male (6.5 × 4.7 mm) (NTOU), Taiwan; G–L, male (10.7 × 8.1 mm) (SMF 37555), Japan.A, carapace; B, right third maxilliped; C, outer view of carpus of right cheliped; D, outer view of left chela; E, male pleon; H, left third maxilliped; F, J, left G1 (ventral view); G, K, left G1 (dorsal view); L, distal part of left G1 (ventral view); M, distal part of left G1 (dorsal view). Scales: B, D, E = 2.0 mm; C, H, J, K = 1.0 mm; I = 2.0 mm; F, G, L, M = 0.5 mm. A–G after Ng & Ho (2003: fig. 3).

FIGURE 40. A–I, left G1 (ventral view); J, right G1 (ventral view; laterally transposed for comparative purposes). A, Typhlocarcinops canaliculatus Rathbun, 1909, male (5.5 × 4.2 mm) (ZRC 1995.0374), Singapore; B, T. canaliculatus Rathbun, 1909, male (8.6 × 6.5 mm) (ZRC 1985.1385), Singapore; C, T. canaliculatus Rathbun, 1909, male (13.2 × 10.5 mm) (ZRC 2018.0696), Hong Kong; D, T. decrescens Rathbun, 1914, male (6.8 × 5.3 mm) (ZRC 2018.0269), Papua, Indonesia; E, T. decrescens Rathbun, 1914, male (6.1 × 4.5 mm) (AS 2137), China; F, T. decrescens Rathbun, 1914, male (15.2 × 11.9 mm) (ZRC 2018.0699), Hong Kong; G, T. denticarpes Dai, Yang, Song & Chen, 1986, male (11.4 × 8.6 mm) (ZRC 2018.0694), Hong Kong; H, T. denticarpes Dai, Yang, Song & Chen, 1986, male (15.9 × 12.4 mm) (ZRC 2018.0700), Hong Kong; I, T. denticarpes Dai, Yang, Song & Chen, 1986, male (14.3 × 10.7 mm) (ZRC 2016.0686), Kyushu, Japan; J, T. yui Ng & Ho, 2003, male (10.7 × 8.1 mm) (SMF 37555), Japan; K, T. robustus n. sp., holotype male (15.2 × 11.3 mm) (MZB Cru 4804), Papua, Indonesia; L, Typhlocarcinops hamus n. sp., holotype male (5.0 × 3.5 mm) (MNHN-IU-2013-1441a), Papua New Guinea.