Typhlocarcinops angustifrons 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 : 64-66

Typhlocarcinops angustifrons Rathbun, 1914

( Figs. 53, 54)

Typhlocarcinops angustifrons Rathbun, 1914: 153 ; Ng 1987: 78; Ng et al. 2008: 144.

Material examined. Holotype: male (14.9 × 11.3 mm) ( USNM 46409 ), station 5220, between Marinduque and Luzon , Philippines, 91 m, coll. RV Albatross, 24 April 1908.

Diagnosis. Carapace ( Fig. 53 A–C) 1.3 times broader than long, surface smooth anteriorly, with granules posteriorly, regions indistinct, H-shaped gastro-cardiac grooves indicated; anterolateral margin arcuate, lined with tiny granules, separated by 2 fissures, forming 3 low, broad lobes; posterolateral surface and margin with scarce, scattered tubercles. Front ( Fig. 53 A–D) bilobed, with shallow median cleft, margin of each lobe slightly convex. Orbit ( Fig. 53D) short, bulbous ocular peduncles filling orbit, immovable, cornea small, slightly pigmented. Epistome ( Fig. 53D) relatively broad, broad triangular median lobe with median suture. Antennal peduncles relatively long. Third maxilliped ( Fig. 53E) with merus broad, squarish, outer and inner margins straight, ischium slightly broader, slightly 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. Cheliped ( Fig. 53A, H) with outer surface of fingers of chela smooth, longitudinal ridge and scattered tubercles proximally on dactylus and fixed finger, surface of palm smooth medially, lower outer surface with scattered prominent tubercles; 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. 53A). Fused thoracic sternites 1, 2 broadly triangular ( Fig. 53F, G), proportionally narrow; thoracic sternites 3, 4 partially fused, with only lateral suture dis- cernible. Male pleon ( Fig. 53F, G) relatively narrow, telson long, 1.8 times as long as somite 6, subtriangular with tapering distal margin. G1 ( Fig. 54) slender, upper half longer than lower half, distal part sinuous with broad, blunt tip, pointed upward. Female not known.

Remarks. This distinctive species is known only from the male holotype from the Philippines. The carapace of the species is similar to that of T. marginatus and T. transversus in the anterolateral armature but the G1 is quite different in having the distal two-thirds gently curved and proportionately much longer ( Fig. 54A, B) than those of these two species. Although the type male of T. angustifrons is much larger than the known specimens of T. marginatus and T. transversus , the G1 differences observed here ( Fig. 54A, B versus Fig. 56A, B and Fig. 60 C‒E respectively) cannot be accounted for by size alone.

Type locality. Between Marinduque and Luzon, Philippines .

Distribution. Philippines, at depths of 91 m.