Typhlocarcinops Rathbun, 1909

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 : 8-9

Genus Typhlocarcinops Rathbun, 1909

Typhlocarcinops Rathbun 1909: 112 ; 1910: 345; 1914: 151; Tesch 1918: 210; Serène 1964: 222; Ng 1987: 89.

Type species. Typhlocarcinops canaliculatus Rathbun, 1909 , by original designation. Gender of genus is masculine.

Diagnosis. Carapace subovate to subrectangular; dorsal surfaces smooth or pubescence; regions indistinct with shallow median H-shaped groove; front bilobed, slightly produced, bent downwards; anterolateral margins arcuate, subcristate (to anterior part of posterolateral margin), granular, with or without lobes, lined with numerous long setae; anterolateral margins not distinctly separated from subparallel posterolateral margins. Epistome relatively broad, subtriangular median lobe with median fissure. Orbital hiatus open, eye peduncle filling orbit, immobile, cornea reduced, sometimes pigmented. Basal antennular article subrectangular; antennules folding vertically. Third maxillipeds with merus subquadrate, anteroexternal angle rounded or auriculiform; ischium rectangular, longer than merus. Male thoracic sternum wide, sternites 1, 2 completely fused to form triangular plate, sternites 3, 4 sometimes fused with only lateral sutures discernible; sternopleonal cavity not reaching to base of sternite 3; press-button mechanism for holding male pleon present as small rounded tubercle on anterior third of sternite 5. Male pleon with somite 1 laterally elongate, touching or almost reaching coxae of fourth ambulatory legs; lateral margin of somite 3 produced forming triangular structures; telson subtriangular. Gl relatively long, slender, curved or sinuous, distal surfaces with scattered spinules; G2 short. Female pleon broad, somite 1 reaching coxae of fourth ambulatory legs, tapering to pointed edge.

Comparative material. Paraselwynia ursina Tesch, 1918 : holotype female (11.5 × 7.7 mm) (NNM-ZMA Crust De 103.315), station 258, Tual , Kei islands, 22 m, coll. M. Webber, Siboga Expedition, 12–16 December 1899.

Remarks. Rathbun (1909) established the genus when she described T. canaliculatus from the Gulf of Thailand. She subsequently described Typhlocarcinops piroculata Rathbun, 1911 , from the Amirante Islands, Indian Ocean and four species from the Philippines ( Rathbun 1914). All of these descriptions were brief and without illustrations. This has proved to be one of the greatest challenges in Typhlocarcinops taxonomy, as the lack of figures restricted later generic studies. Tesch (1918) reviewed the status of the genus, provided a key, noted that T. piroculatus should be assigned to Typhlocarcinodes Alcock, 1900 , and described two new species from eastern Indonesia, T. angustipes and T. transversus . Records of species from Indonesia by Rathbun (1914), Japan and China by Tesch (1918), Yokoya (1933), Sakai (1935, 1939, 1965, 1976), Serène (1964), Dai et al. (1986), Dai & Yang (1991) are all in doubt as these authors relied wholly on Rathbun’s (1914) brief descriptions or had colleagues check specimens for them. In the intervening years, Türkay (1986) figured the holotype of T. marginata and its G1 when comparing it to his new species, T. serenei . Sakai (1976) provided simple figures of the carapace and chelipeds of the type of T. ocularius . Dai et al. (1986) figured the type of T. ocularius , noting that while it was not formally known from China, it was probably found there, and they therefore included it in the Chinese fauna. Ng (1987: 91) later noted that the structure of the male pleonal somite 1 of Ceratoplax arcuata Miers, 1884 (from Darwin, Australia) was extremely wide (cf. Miers 1884: pl. 25b’) and it should be assigned to Typhlocarcinops .

Some of the taxa originally included in the Rhizopinae are now shown to belong to other families, notably the Acidopsidae Števčić, 2005 (see Ng & Rahayu 2014), with T. piroculata referred to the acidopsid genus Raoulia Ng, 1987 . As such, it seemed important to figure the material of Rathbun (1914) and some species of Tesch (1918) in the present paper. This would greatly improve the comparisons of new species recognized by the present work and aid future studies of the group.

Three species are here regarded as synonyms: T. gallardoi Serène, 1964 , with T. canaliculatus Rathbun, 1909 ; T. genkaiae Takeda & Miyake, 1972 , with T. decrescens Rathbun, 1914 ; and T. takedai Ng, 1987 , with T. marginatus Rathbun, 1914 . Most of the current species have been described from Southeast Asia and the western Pacific, with only two ( T. stephenseni Serène, 1964 , and T. serenei Türkay, 1986 ) known from the Indian Ocean. Although Serène & Soh (1976: 20) commented that they had five or six species from the Andaman Sea, they did not have time to work on them.

For the present sudy, nine new species are recognised and more are added to the Indian Ocean fauna ( T. canaliculatus Rathbun, 1909 , T. atimovatae n. sp. and T. hadrotes n. sp.).