Typhlocarcinops marginatus Rathbun, 1914

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 : 66-68

Typhlocarcinops marginatus Rathbun, 1914

( Figs. 55 , 56 )

Typhlocarcinops marginata Rathbun, 1914: 152 ; Türkay 1986: 165, text fig. 58, pl. 4 figs. 17, 18; Ng 1987: 78. Typhlocarcinops marginatus — Ng et al. 2008: 144.

Typhlocarcinops transversa — Takeda & Miyake 1968: 569, pl. 6A, figs. 8a, b (not Typhlocarcinops transversa Tesch, 1918 ). Typhlocarcinops takedai Ng, 1987: 90 ; Ng & Huang 2002: 1380, fig. 1; Ng et al. 2008: 144; Ng et al. 2017: 63.

Material examined. Holotype: male (8.1 × 6.3 mm) ( USNM 46395 ), station 5426, off eastern Palawan, Philippines, 49 m, coll. RV Albatross, 3 April 1909.

Diagnosis. Carapace ( Fig. 55A, B ) 1.3 times broader than long, surface pubescent, margin fringe with sparse setae, regions indistinct, H-shaped gastro-cardiac grooves slightly indicated; anterolateral margin arcuate, lined with tiny granules, separated by 3 depressions, forming 4 low, broad lobes; posterolateral surface and margin with scarce, scattered tubercles. Front ( Fig. 55B, C ) slightly bilobed, with shallow median cleft, margin of each lobe slightly convex. Orbit ( Fig. 55C ) short, bulbous ocular peduncles filling orbit, immovable, cornea small, well pigmented. Epistome ( Fig. 55C ) relatively broad, broad triangular median lobe with median suture. Antennal peduncles relatively long. Third maxilliped ( Fig. 56A ) with merus broad, squarish, anteroexternal angle slightly expanded, auriculiform, outer and inner margins straight, ischium slightly broader, longer than merus, inner margin slightly shorter than outer margin, lower margin slightly oblique; exopod relatively slender, tip reaching to just before distal edge of merus. Chelipeds unequal ( Fig. 55A, F, G ) subequal, outer surface of fingers of chela smooth, major chela with longitudinal ridge on dactyle, groove on fixed finger; minor chela with longitudinal ridge on dactylus and fixed finger, surface of palm with scattered tubercles on half lower outer surface, tubercles denser and stronger on minor cheliped; cutting edges of fingers with prominent teeth; upper and lower outer surface of carpus with small tubercles, smooth medially, inner angle without protuberance, with short, broad tooth ( Fig. 55A ). Fused thoracic sternites 1, 2 broadly triangular ( Fig. 55D, E ), proportionally narrow; thoracic sternites 3, 4 partially fused, with only lateral suture discernible. Male pleon ( Fig. 55D, E ) relatively narrow, telson long, 1.8 times as long as somite 6, subtriangular with rounded distal margin. G1 ( Fig. 56B, C ) slender, upper and lower halves subequal, sinuous, distal part with blunt tip directed upward. Female not known.

Remarks. This species was described from a single Philippines male. Serène (1964) recorded the species from Indonesia, but his record of “ T. marginatus ” is not this species and should be referred to T. hadrotes n. sp. instead (see discussion for that species). Türkay (1986) figured the type and its G1 of T. marginatus when he compared his new species, T. serenei , from the Red Sea with it.

Ng (1987) referred Takeda & Miyake’s (1968) record of “ T. transversus ” from Japan to a new species, T. takedai , noting that it differed from that species in various carapace and cheliped characters. Ng & Huang (2002) subsequently reported T. takedai from Taiwan (see also Ng et al. 2017). Typhlocarcinops takedai agrees well with the type male of T. marginatus in all major aspects and we are confident both are synonyms.

Typhlocarcinops marginatus is superficially similar to T. transversus in the wide carapace with low lobes on the anterolateral margin. Although the carapace of adult T. transversus is proportionately wider ( Fig. 58 versus Fig. 55A, B ), smaller specimens are harder to separate. The third maxilliped and the G1 are the most reliable way to separate the two species, being constant even in small specimens. In T. marginatus , the anteroexternal angle is distinctly projected and auriculiform ( Fig. 56A ), whereas in T. transversus , the anteroexternal angle is rounded and not auriculiform ( Fig. 60A ). In T. marginatus , the G1 is evenly sinuous with the upper and lower parts subequal in length with the tip straight ( Fig. 56B, C ), versus the upper part of the G1 is proportionately longer and is almost straight, with the tip bent at an angle ( Fig. 60 C–G) in T. transversus ,

Type locality. Eastern Palawan, Philippines .

Distribution. Eastern Palawan, Philippines, 49 m.

Figures

FIGURE 55. Typhlocarcinops marginatus Rathbun, 1914, holotype male (8.1 × 6.3 mm) (USNM 46395), Palawan, Philippines. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, anterior thoracic sternum and pleon; E, posterior thoracic sternum and pleon; F, outer view of right chela; G, outer view of left chela.

FIGURE 56. Typhlocarcinops marginatus Rathbun, 1914, holotype male (8.1 × 6.3 mm) (USNM 46345), Palawan, Philippines. A, left third maxilliped; B, left G1 (ventral view); C, left G1 (dorsal view). Scales = 0.5 mm.

FIGURE 58. Typhlocarcinops transversus Tesch, 1918. A, C, male (7.5 × 5.5 mm) (ZRC 2018.0272), Philippines; B, D, female (7.3 × 5.0 mm) (ZRC 2018.0271), Sunda Strait, Indonesia. A, B, overall habitus; C, D, dorsal view of carapace.

FIGURE 60. Typhlocarcinops transversus Tesch, 1918. A, B, D–G, male (7.5 × 5.5 mm) (ZRC 2018.0272), Philippines; C, holotype male (8.0 × 4.1 mm) (NNM-ZMA De 103.003), Sumbawa, Indonesia. A, left third maxilliped; B, male pleon; C, right G1 (ventral view); D, left G1 (ventral view); E, left G1 (dorsal view); F, distal part of left G1 (ventral view); G, distal part of left G1 (dorsal view). Scales: A, D, E = 0.5 mm; B, C = 1.0 mm; F, G = 0.25 mm. C after Türkay (1986: text fig 59).