A synopsis of Typhlocarcinops Rathbun, 1909 (Crustacea: Decapoda: Brachyura: Pilumnidae), with descriptions of nine new species from the Indo-West Pacific Author Ng, Peter K. L. Author Rahayu, Dwi Listyo text Zootaxa 2020 2020-06-05 4788 1 1 100 journal article 10.11646/zootaxa.4788.1.1 1175-5326 3878222 7A461DBA-00B7-48DB-9320-4775DA8F21B2 Typhlocarcinops diminutus n. sp. ( Figs. 67–69 ) Material examined . Holotype : male (3.5 × 2.5 mm ) ( ZRC 2018.0295 ), dredge, station PS252, Pulau Semakau , Singapore , coll. 1990s . Paratypes : 3 males (4.2 × 2.9 mm , 2.9 × 2.4 mm , 3.3 × 2.7 mm ); 2 females 3.8 × 2.9 mm , 2.9 × 2.2 mm ); 1 ovigerous female (3.6 × 2.7 mm ) ( ZRC 1992 5955–5999), Pulau Semakau , Singapore , coll. 27 January 1992 . FIGURE 67 . Typhlocarcinops diminutus n. sp . , male (3.5 × 2.5 mm) (ZRC 2018.0295), Singapore. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, anterior thoracic sternum and telson; E, subdorsal view of right cheliped (denuded); F, outer view of right chela; G, outer view of right chela (denuded); H, left fourth ambulatory leg (denuded). FIGURE 68 . Typhlocarcinops diminutus n. sp . A, B, paratype ovigerous female (3.6 × 2.7 mm) (ZRC 1992.5953), Singapore; C, E, F, paratype female (3.8 × 2.9 mm) (ZRC 1992.5954), Singapore; D, paratype male (4.2 × 2.9 mm) (ZRC 1992.5952), Singapore. A, overall habitus; B–D, dorsal view of carapace; E, anterior thoracic sternum and pleon; F, sternopleonal cavity and vulvae. Diagnosis . Carapace ( Figs. 67A, B , 68 A–D) 1.2−1.4 times broader than long, slightly narrowing on posterolat- eral margin, surface with tufts of short plumose setae, regions demarcated, H-shaped gastro-cardiac grooves shallow, indistinct, anterolateral margin arcuate, lined with small granules, separated by 3 broad, sharp teeth; posterolateral margin subparallel posterolateral surface with scattered tubercles. Front bilobed ( Figs. 67B , 68 B–D), with shallow median cleft, margin of each lobe convex. Orbit ( Fig. 67C ) short, bulbous ocular peduncles filling orbit, immovable, cornea small, pigmented. Epistome ( Fig. 67C ) relatively broad, triangular median lobe with slight median suture. Antennal peduncles long. Third maxilliped ( Figs. 67C , 69A ) with outer surface of merus covered with small granules on distal margin, outer margin straight, inner margin sinuous, anteroexternal angle gently produced; ischium as broad, but much longer than merus, inner margin slightly shorter than outer margin; exopod relatively slender. Chelipeds unequal in males, subequal in females ( Figs. 67 E–G, 68A), 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, carpus and merus smooth, tufts of sparse setae on its surfaces; inner angle of carpus with sharp low tooth ( Fig. 67E ). P2−P5 proportionally long ( Figs. 67A, H , 68A ); dorsal margin of the merus of first to third ambulatory legs smooth, unarmed; lateral surface, dorsal and ventral margins fringe with long setae; dactylus straight, relatively long; merus of P5 not reaching front when folded. Fused thoracic sternites 1, 2 broadly triangular ( Fig. 67C, D ), proportionally narrow; thoracic sternites 3, 4 fused, suture discernible. Male pleon ( Fig. 69B ) relatively broad; telson relatively short, 1.5 times as long as somite 6, with rounded distal margin. G1 ( Fig. 69C, D ) slender, upper and lower halves subequal, moderately curved, distal part strongly curved, relatively long and slender, tapering to relatively sharp tip, with setae subdistally. Female pleon ( Fig. 68E ) broad, somite 1 reaching coxae of fourth ambulatory legs; telson with rounded distal margin; tapering to pointed edge; vulva ( Fig. 68F ) relatively broad, rounded. Etymology . From the Latin “diminutus” for small sized, alluding to the small adult size of the species. Remarks . The general appearance of the species superficially resembles members of Heteropilumnus De Man, 1895 , and its allies ( Ser Rathbun, 1931 ; Zehntneriana Ng & Takeda, 2010 ), except that it lacks the long setae that lines the margins of the carapace, chelipeds and ambulatory legs and/or the dense velvet-like tomentum that covers the carapace (cf. Ng 1989 ; Ng & Davie 1991 ; Ng & Lin 2015 ; Ng & Tan 1988 ; Ng et al. 2018 ; Lee et al. 2015 ). FIGURE 69 . Typhlocarcinops diminutus n. sp. , male (3.5 × 2.5 mm) (ZRC 2018.0295), Singapore. A, right third maxilliped; B, pleon; C, left G1 (ventral view); D, left G1 (dorsal view). Scales: A, C, D = 0.5 mm; B = 1.0 mm. Like any other species assigned to Typhlocarcinops , the anterolateral margin of carapace is varied in relation with size and sex. The larger male (carapace width 4.2 × 2.9 mm ) and the females have less pronounced lobes on the anterolateral margin than the small one. The dactylus and fixed finger of the chelipeds of the larger male are without longitudinal ridge. The species most resembles T. canaliculatus , but differs in the shape of the carapace in which the posterolateral margin is slightly narrowing, the G1 with the upper and lower halves are subequal, moderately curved in T. diminutus n. sp. ( Figs. 67A, B , 68 B‒D, 69C, D), versus the posterolateral margin of the carapace is parallel and the upper half of G1 is much longer than the lower half, strongly curved in T. canaliculatus ( Figs. 5B, C , 7A, D , 8B , 9B, C , 10A , 11B , 12B , 13 D‒G, I‒L, 14B‒E, H‒K, 15E‒G, 40A–C). Type locality . Pulau Semakau , Singapore . Distribution . Singapore ; from shallow subtidal habitats with soft substrates less than 20 m depth.