Typhlocarcinops hamus, Ng & Rahayu, 2020

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 : 46-48

Typhlocarcinops hamus n. sp.

( Figs. 38 , 39 , 40L )

Material examined. Holotype: male (5.0 × 3.5 mm) (MNHN-IU-2013-1441a), station PD73, Yomba Island , 0514.7’S 14547.3’E, 20–25 m, Papua New Guinea, coll. Expedition Papua Niugini, 6 December 2012 . Paratypes: 1 male (3.6 × 2.6 mm) (MNHN-IU-2013-1441b), 2 males (4.6 × 3.2 mm, 4.1 × 3.0 mm) ( ZRC 2018.0735 ), same data as holotype. Others : 1 poorly preserved male (4.1 × 2.8 mm) (with Sacculina ) ( ZRC 2019.1704 ), stn PD73, Yomba Island, 05°14.7’S 145°47.3’E, 20-25 m, Papua New Guinea, coll. A. Anker, Expédition PAPUA NIUGINI, 6 December 2012 .

Diagnosis. Carapace about ( Fig. 38A, B ) 1.4 times broader than long, surface glabrous medially, slightly narrowing on posterolateral margin, regions demarcated, H-shaped gastro-cardiac grooves shallow, indistinct, anterolateral margin arcuate, lined with small granules, separated by 2 shallow depressions, forming 3 broad lobes; posterolateral margin subparallel antero and posterolateral surface with scattered tubercles. Front bilobed ( Fig. 38B, C ), with shallow median cleft, margin of each lobe convex. Orbit ( Fig. 38B, C ) short, bulbous ocular peduncles filling orbit, immovable, cornea small, pigmented. Epistome ( Fig. 38C ) relatively broad, triangular median lobe with slight median suture. Antennal peduncles long. Third maxilliped ( Fig. 39A ) with outer margin of merus broad, outer and inner margins straight, anteroexternal angle rounded; ischium slightly broader, but much longer than merus, inner margin slightly shorter than outer margin; exopod relatively slender. Chelipeds unequal in males ( Fig. 38A, G, H ), fingers of major chela smooth, outer surface of dactylus and fixed finger with longitudinal ridge, long fine setae on upper and lower margins of dactylus and fixed finger, cutting edges with prominent broad teeth; palm with sparse granules on upper and lower outer surface, smooth medially, carpus and merus smooth, tufts of sparse setae on its surfaces; carpus without protuberance ( Fig. 38E, F ). P2−P5 proportionally long ( Fig. 38A ), dorsal and ventral mar- gins fringe with sparse, long setae; dactylus straight; merus of P5 not reaching front when folded. Fused thoracic sternites 1, 2 broadly triangular ( Fig. 38D ), proportionally narrow; thoracic sternites 3, 4 fused, suture discernible. Male pleon ( Figs. 38D , 39B ) relatively broad; telson relatively long, 1.7 times as long as somite 6, with rounded distal margin. G1 ( Figs. 39 C–F, 40L) slender, slightly curved, upper half longer than lower half, distal part strongly curved, directed inwards, ending in pointed tip, with setae subdistally.

Etymology. The name is derived from the Latin for hook, alluding to the G1 structure. The name is used as a noun.

Remarks. The curved G1 distal part in T. hamus n. sp. is a character shared with T. raouli n. sp., which differs in the degree of curvature. In T. raouli n. sp., the curved distal part form is hook-shaped with a flared and rounded tip that is directed obliquely laterally ( Fig. 44 C–F) versus strongly curved with the pointed tip directed inwards in T. hamus n. sp. ( Figs. 39 C–F, 40L).

Type locality. Yomba Island , Papua New Guinea .

Distribution. Only known from Yomba Island, Papua New Guinea. From depths of 20− 25 m.

Figures

FIGURE 38. Typhlocarcinops hamus n. sp., holotype male (5.0 × 3.5 mm) (MNHN-IU-2013-1441a), Papua New Guinea. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, anterior thoracic sternum and pleon; E, carpus of left cheliped; F, carpus of right cheliped; G, outer view of right chela; H, outer view of left chela.

FIGURE 39. Typhlocarcinops hamus n. sp., holotype male (5.0 × 3.5 mm) (MNHN-IU-2013-1441a), Papua New Guinea. A, left third maxilliped; B, male pleon; C, left G1 (ventral view); D, left G1 (dorsal view); E, distal part of left G1 (ventral view); F, distal part of left G1 (dorsal view). Scales: A–D = 0.5 mm; E, F = 0.1 mm.

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.

FIGURE 44. Typhlocarcinops raouli n. sp., holotype male (8.0 × 5.7 mm) (MZB Cru 4806), Papua, Indonesia. A, left third maxilliped; B, male pleon; C, left G1 (ventral view); D, left G1 (dorsal view); E, distal part of left G1 (ventral view); F, distal part of left G1 (dorsal view). Scales: A–D = 1.0 mm; E, F = 0.5 mm.