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 canaliculatus Rathbun, 1909 ( Figs. 2A , 3 , 5–15 , 40 A–C) Typhlocarcinops canaliculata Rathbun, 1909: 112 ; 1910: 345 , text fig. 32, pl. 2 fig. 16; Tesch 1918: 211 ; Sakai 1935: 190 , textfig. 99, pl. 55, fig. 2; 1939: 571, text-fig. 67, pl. 68, fig. 2; 1976: 545, text-figs. 292 a, b, pl. 195 fig. 1; Dai et al. 1986: 383 , text fig. 202(1), pl. 55(6); Ng 1987: 90 ; Dai & Yang 1991: 413 , text fig. 202(1), pl. 55(6). Typhlocarcinops gallardoi Serène, 1964: 230 , text-fig. 11, pl. 20B; Ng et al. 2008: 144 . Typhlocarcinops canaliculatus — Ng et al. 2008: 144 . Material examined . Holotype : male (3.5 × 2.9 mm ) ( NHMD 5956 ), between Koh Mesan and Cap Liant, Gulf of Thailand , 9–15 m , coll. Th. Mortensen , 2 July 1900 . Others. 1 male (carapace width ca. 1.8 mm , badly dismembered) ( USNM 39751 ), sandstone bottom, south of Koh Mak , Gulf of Thailand , 9–11 m , coll. Th. Mortensen , 17 February 1900 ; 1 male (8.7 × 6.6 mm ) ( ZRC 1984.7749 ), Bangtao Bay , west coast of Phuket , Andaman Sea , western Thailand , coll. B. Chatananoaj , 22 February 1982 ; 1 male (5.5 × 4.2 mm ), 1 female (5.8 × 4.2 mm ) ( ZRC 1995.0374 ), Johor Shoal , Singapore , coll. May 1992 ; 1 male (8.6 × 6.5 mm ) ( ZRC 1985.1385 ), mud and sand substrate, 1 mile west of station B45, 11 m, coll. Singapore Regional Fisheries Research Station , 1960s; 1 male (4.2 × 2.9 mm ) ( ZRC 2018.0719 ), station DR 2, between Lazarus and mainland, Singapore , 01°13.991’ N 103°50.967’E , coll. 23 April 2012 ; 1 female (10.1 × 7.4 mm ) ( ZRC 2018.0277 ), Bangka , Riau Islands , Indonesia , coll. 30 May 2002 ; 1 male (13.2 × 10.5 mm ) ( ZRC 2018.0696 ), Lantau , Hong Kong , coll. University of Hong Kong trawls, 28 July 2007 ; 1 male (12.4 × 9.6 mm ) ( ZRC 2018.0739 ), Lantau , Hong Kong , coll. University of Hong Kong trawls, 30 July 2018 . Diagnosis . Carapace subovate ( Figs. 5 A–C, 6A, B, 7A, D, 8B, 9B, C, 10A, 11B), 1.2–1.4 times broader than long, front bilobed, with shallow broad, median cleft, margin of each lobe slightly convex. Orbit ( Figs. 5D , 8C , 9D , 11C ) short, bulbous ocular peduncles filling orbit, immovable, cornea small, slightly pigmented. Epistome ( Figs. 5D , 8C , 9D , 11C ) relatively broad, triangular median lobe with median suture. Antennal peduncles relatively long. Third maxillipeds ( Figs. 6D, E , 7E , 13B , 14A, F , 15B ) with merus broad, squarish, outer and inner margins straight, ischium slightly broader, much longer than merus, inner margin slightly shorter than outer margin, lower margin slightly oblique; exopod relatively slender. Chelipeds unequal in males, subequal in females ( Figs. 5A , E–G, 7B, F, 8A, E, F, 9A, G, H, 10C–F, 11F–H), outer surface of fingers of major chela smooth, with low longitudinal ridge and scattered tubercles proximally on dactylus, longitudinal groove on fixed finger, surface of palm smooth medially, upper, lower outer surface with scattered tubercles; cutting edges of fingers with prominent teeth; upper outer surface of carpus with tubercles, smooth medially, distinct tooth on inner angle, smaller tooth basally ( Figs. 5E , 10C, D , 11G, H ); lower outer surface of merus with scattered tubercles, margins covered with long setae. P2−P5 ( Figs. 5A , 7A , 8A , 9A , 11A ) proportionally long, fringe by long setae on dorsal and ventral margins; merus of P5 not reaching front when folded. Fused thoracic sternites 1, 2 broadly triangular ( Figs. 6C , 8D , 9E, F , 10B , 11D ), proportionally narrow; thoracic sternites 3, 4 partially fused, with only lateral suture discernible. Male pleon ( Figs. 6F , 7C, G , 13C, H , 14G , 15C, D ) relatively broad, telson long, 1.6–1.8 times as long as somite 6, subtriangular with rounded distal margin. G1 ( Figs. 13 D–G, I–L, 14B–E, H–K, 15E‒G, 40A–C) slender, upper half longer than lower half, strongly curved, distal part short, slightly curved, with pointed tip. Female pleon ( Fig. 12C ) broad, somite 1 reaching coxae of fourth ambulatory legs, tapering to pointed edge; telson subtriangular; vulva ( Fig. 12D ) large, ovate. Redescription. Carapace subovate, 1.2–1.4 times broader than long; dorsal surfaces mostly smooth, sparse granules dorsolaterally, regions poorly defined, H-shaped gastro-cardiac grooves shallow but clearly indicated ( Figs. 5 A–C, 6A, B, 7A, D, 8A, B, 9A–C, 10A, 11A, B, 12A, B, 15A). Front bilobed, with shallow broad median longitudinal depression; margin smooth, gently convex from dorsal view ( Figs. 5D , 8C , 9D , 11C ). Orbit broad, supraorbital margin gently granular, entire ( Figs. 5D , 8C , 9D , 11C ). Anterolateral margins prominently arcuate, lined with tiny granules, entire or with 4 low lobes/teeth; anterolateral margins gradually confluent with posterolateral margins; posterolateral margins subparallel with slightly produce lower margin; posterolateral surface and margin with scarce, scattered tubercles. Posterior carapace margin gently convex ( Fig. 5B, C ). Suborbital margin entire, without tooth. Suborbital region gently granular ( Figs. 9D , 11C ). Eyes relatively stout, completely filling orbit, immobile, bulbous, with small pigmented cornea ( Figs. 5D , 7D , 8C , 9D , 11C , 13A ). Antennal peduncles relatively long, basal article transversely rectangular, article 3 and 4 longer than wide. Third maxillipeds relatively short, completely covering buccal cavern when closed; palp (dactylus, propodus, carpus) short, tip of dactylus barely reaching distal margin of ischium; merus squarish, shorter than ischium, surface slightly convex, anterolateral angle rounded, not produced; ischium subquadrangular, 1.2 as long as broad, with very shallow sublateral sulcus; exopod narrow, reaching distal margin of merus, with long flagellum ( Figs. 6D, E , 7E , 8D , 9E , 13B , 14A, F , 15B ). Male chelipeds unequal, subequal in females; with short, plumose setae lining merus, carpus; outer surface of fingers of major chela smooth, with low longitudinal ridge and scattered tubercles proximally on dactylus, shallow longitudinal groove on fixed finger, surface of palm smooth medially, upper, lower outer surface with scattered tubercles; cutting edges of fingers with prominent teeth; upper outer surface of carpus with tubercles, smooth medially, distinct tooth on inner angle, smaller tooth basally ( Figs. 5 E–G, 7B, F, 8E, F, 9G, H, 10C‒F, 11F−H, 12A); lower outer surface of merus with scattered tubercles, margins covered with long setae. P2−P5 ( Figs. 5A , 7A , 8A , 11A , 12A ) proportionally long; P3 longest; dactylus elongated, as long as propodus, fringe with sparse long setae on dorsal and ventral margins of all segments; merus of P5 not reaching front when folded. FIGURE 5 . Typhlocarcinops canaliculatus Rathbun, 1909 , holotype male (3.5 × 2.9 mm) (NHMD 5956), Gulf of Thailand. A, overall habitus; B, C, dorsal surface of carapace from different angles; D, frontal view of cephalothorax; E, dorsal view of right cheliped; F, outer view of right chela; G, outer view of left chela. Fused thoracic sternites 1, 2 broadly triangular ( Figs. 6C , 8D , 9E , 10B , 11D ), proportionally narrow; thoracic sternites 3, 4 partially fused, with only lateral suture discernible. Male pleon ( Figs. 6F , 7C, G , 10B , 11D, E , 13C, H , 14G , 15C, D ) relatively broad; somite 1 extremely broad, medially narrow, tapering laterally to pointed edge, reaching coxae of fourth ambulatory legs; somite 2 rectangular, short, laterally slightly narrowing; somite 3 expanded laterally, forming triangular structure; somites 4–6 wider than long, rectangular, lateral margins almost straight or slightly concave; telson long, 1.6–1.8 times as long as somite 6, subtriangular with lateral margins gently convex, tip rounded. G1 ( Figs. 13 D–G, I–L, 14B–E, H–K, 15E‒G, 40A– C) slender, upper half longer than lower half, strongly curved, distal part short, slightly curved, with pointed tip. FIGURE 6 . Typhlocarcinops canaliculatus Rathbun, 1909 , holotype male (3.5 × 2.9 mm) (NHMD 5956), Gulf of Thailand. A, left anterolateral margin (denuded); B, right anterolateral margin (denuded); C, anterior thoracic sternum; D, right third maxilliped; E, left third maxilliped; F, pleon. Scales = 0.5 mm. Female pleon ( Figs. 12C , 15H ) broad, somite 1 conspicuously broad with sharply tapering acutely triangular lateral margin, reaching coxae of fourth ambulatory legs; telson subtriangular; vulva ( Fig. 12D ) large, ovate, without operculum. Remarks . This species was briefly described without figures by Rathbun (1909) from one male collected from the Gulf of Thailand . Rathbun (1910: 345 , text fig. 32, pl. 2 fig. 16) redescribed the species, adding a figure of the species and four drawings. In 1910, she noted that in addition to the type male listed in 1909, she had another male specimen from south of Koh Mak, Gulf of Thailand , but without any measurements. While she indicated that plate was based on the type male measuring 3.6 mm in carapace width, she did not mention which specimen was drawn. In the USNM is a badly damaged male approximately 1.8 mm in carapace width from south of Koh Mak (USNM 39751) which also has a small label with the writing “4 drawings”, indicating that Rathbun’s (1910 : text fig. 32) four figures were based on this specimen (reproduced here as Fig. 7 C–G). FIGURE 7 . Typhlocarcinops canaliculatus Rathbun, 1909 , non-type male (carapace width ca. 1.8 mm, badly crushed) (USNM 39751), Gulf of Thailand, Thailand. A, overall habitus; B, F, outer view of right chela; C, somites 1–3 of male pleon; D, dorsal view of carapace; E, left third maxilliped; G, male pleon. Scales = 0.5 mm. D–G after Rathbun (1910 : fig. 32). The study of the two specimens from the Gulf of Thailand show that Rathbun’s (1910) descriptions and figures are inaccurate. The anterolateral margin of the carapace of the two specimens was described and figured as entire but it is actually not the case. The right anterolateral margin of the type male actually has four of the granules relatively larger although the margin can still be described as approximately entire ( Figs. 6B , 7D ). The left anterolateral margin of the type male, however, is different, with four tubercles which clearly indicate the position of four low lobes ( Figs. 5 A–C, 6A). The anterolateral margins of the carapace of the smaller non-type male from the Gulf of Thailand (USNM 39751), although in a poor condition, also has some of the granules slightly larger like that of the type male, although it is relatively lower and more like what Rathbun (1910 : fig. 32a) figured ( Fig. 7A ). It thus appears that smaller specimens have a relatively more entire anterolateral margin, with the four lobes becoming more obvious in larger specimens, but there is clearly more variation than has been described. The male pleon figured by Rathbun (1910 : fig. 32b; present Fig. 7G ) shows a relatively slender structure with somite 1 extremely broad. Most of the pleon of the non-type specimen she drew this from is missing but fortunately the first few somites are still extant. Somite 1 is not as wide as depicted and the lateral margins of somite 3 are also not as angular ( Fig. 7C ). The first three somites of the male pleon of the holotype male closely resembles that of the non-type male ( Fig. 6F ) and overall, it is proportionately broader ( Fig. 6F ) than what was figured by Rathbun (1910 : fig. 32b; present Fig. 7G ). The third maxilliped and chela she figured ( Rathbun 1910 : fig. 32c, d; present Fig. 7E ), however, is relatively accurate ( Fig. 6D, E ). FIGURE 8 . Typhlocarcinops canaliculatus Rathbun, 1909 , male (5.5 × 4.2 mm) (ZRC 1995.0374), Singapore. A, overall habitus; B, dorsal view of carapace; C, frontal view of cephalothorax; D, anterior thoracic sternum; E, outer view of left chela; F, outer view of right chela. FIGURE 9 . Typhlocarcinops canaliculatus Rathbun, 1909 , male (8.6 × 6.5 mm) (ZRC 1985.1385), Singapore. A, overall habitus; B, C, dorsal view of carapace; D, frontal view of cephalothorax; E, anterior thoracic sternum; F, sternopleonal cavity showing pleonal locking tubercles; G, outer view of right chela; H, outer view of left chela. It is also important to note that the holotype male of T. canaliculatus is a juvenile male, with the gonopods barely developed, being neither chitinised or sinuous. As such, the structure of its male pleon ( Fig. 6F ) is likely to change in shape with size. Notably, the lateral margins of somite 3 will become more angular as the crabs get larger and more mature, and the overall structure also becomes slightly wider transversely. In the ZRC are four specimens, three males and a female ( ZRC 1985.1385 , ZRC 1995.0374 , ZRC 2018.0719 ), which are clearly referable to T. canaliculatus s. str. as defined here. The anterolateral margins of the specimens vary. The anterolateral margins of the female specimen (which has the right swollen due to a bopyrid infection, ZRC 1995.0374 b) are entire ( Fig. 12B ), but the right anterolateral margin of a smaller male ( ZRC 1995.0374 a) is weakly lobate, with a shallow cleft demarcating the last lobe, although the left margin is more entire ( Fig. 8B ). The larger male ( ZRC 1985.1385 ) has the anterolateral teeth weakly dentate and resembles the smaller male except that its frontal margin is relatively more produced ( Fig. 9D versus Fig. 8C ). The outer surface of chela of the smaller male and female from Singapore ( ZRC 1995.0374 ) closely resembles that of the type , possessing the relatively short chelae of this species and the median part of the outer surface is granulated and rugose ( Fig. 8E, F ). The larger male ( ZRC 1985.1385 ) has a similar chela except that the fingers are proportionately longer and the outer surface is less granulated and setose ( Fig. 9G, H ). The G 1 of the smaller male ( ZRC 1995.0374 ) is distinct in that the lower half is distinctly shorter than the upper half and the distal part is quite short and gently curved ( Fig. 40A ). The G 1 of the larger male ( ZRC 1985.1385 ) is similar to shape and proportions to the smaller male except that the distal part is relatively more elongate ( Fig. 40B ). There is also a male from Phuket in western Thailand from the Andaman Sea ( ZRC 1984.7749 ) which agrees very well with the larger Singapore specimen except that its last two anterolateral teeth are more marked even though both are still relatively low ( Fig. 10A ). Its other characters, including the form of the chela, pleon and G1 are almost the same ( Figs. 10 B–F, 14B–E). The male (13.2 × 10.5 mm , ZRC 2018.0696 ) from Hong Kong agrees with the other material in all aspects except that its anterolateral margin is the most distinctly lobate ( Fig. 11B ). Significantly , its G1 ( Fig. 14 H–K) closely resembles those from Singapore and Thailand . FIGURE 10 . Typhlocarcinops canaliculatus Rathbun, 1909 , male (8.7 × 6.5 mm) (ZRC 1984.7749), Phuket. A, dorsal view of carapace; B, anterior thoracic sternum and pleon; C, dorsal view of left cheliped; D, dorsal view of right cheliped; E, outer view of right chela; F, outer view of left chela. FIGURE 11 . Typhlocarcinops canaliculatus Rathbun, 1909 , male (13.2 × 10.5 mm) (ZRC 2018.0696), Hong Kong. A, overall habitus; B, dorsal surface of carapace (denuded); C, frontal view of cephalothorax; D, anterior thoracic sternum and pleon; E, posterior thoracic sternum and pleon; F, outer view of chelae; G, dorsal view of left chela; H, dorsal view of right chela. The study of the present material from Thailand , Singapore and Hong Kong demonstrates that Typhlocarcinops gallardoi Serène, 1964 , is a junior synonym of T. canaliculatus s. str. Typhlocarcinops gallardoi was described by Serène (1964) on the basis of a male (6.5 × 5.3 mm ) from Java Sea and a female (6.3 × 5.0 mm) from Makassar, but he did not indicate which was the holotype ; as such both specimens are syntypes . The male in NHMD, which was figured by Serène (1964) is here designated as the lectotype . Serène (1964) provided a photograph of the type male but no details of the carapace were visible. He, however, described the anterolateral margin as lined with three low lobes, a character he notes as shared with T. marginatus and T. transversus ( Serène, 1964: 230 ) . As discussed above, the present specimens of T. canaliculatus from Singapore have the anterolateral margins varying from almost entire ( Fig. 12B ), weakly dentate ( Fig. 8B ) to with three low but distinct lobes ( Fig. 9B ). The Hong Kong male specimen has the anterolateral margin most obviously dentate ( Fig. 11B ). The G1 of T. gallardoi ( Fig. 15 E–G) agrees well with what is here described for T. canaliculatus ( Figs. 13 D–F, I–L, 14B–E, H–K). Comparing the present specimens of T. canaliculatus with T. decrescens , several differences are obvious. The structure of the anterolateral margin is not a reliable character as it is also known to vary in T. decrescens , from almost entire ( Fig. 20A ) to weakly but distinctly lobate ( Fig. 21A ). The form of the chelae is distinct, the palm of the chela and fingers are proportionately shorter and setose all over T. canaliculatus ( Fig. 8E, F ) (versus palm and fingers proportionately longer with the median parts glabrous in T. descrescens ; cf. Fig. 21E, F ); the carapace has the gastro-cardiac grooves relatively deeper and distinct (best determined by running a sharp pincer over the surface) ( Fig. 11B ) (versus carapace surface smoother with the gastro-cardiac grooves very shallow and almost undicernible, appearing smooth in T. descrescens ; cf. Fig. 16B ); the posterior margin of the epistome is markedly concave ( Fig. 13A ) (versus margin gently concave to almost straight in T. descrescens ; cf. Fig. 16C ); the distal part of the G1 is relatively short ( Fig. 40 A–C) (versus distal part prominently elongate in in T. descrescens ; cf. Fig. 40 D‒F); and the vulvae are more obliquely elongate ( Fig. 12D ) (versus more ovate in in T. descrescens ; cf. Fig. 17D ). The specimens referred to “ Typhlocarcinops ? canaliculatus ” by Serène (1964: 226 , fig. 9) from Indonesia are clearly not this species, as has been suggested by Dai et al. (1986) and Dai & Yang (1991) . They are here referred to a new species, T. raouli (see below). Sakai (1935 , 1939 , 1976 ) recorded “ T. canaliculata ” from Shimoda and Tosa Bay in Japan , and he figured the third maxilliped and male pleon ( Sakai 1939 : text-fig. 67a, b; 1976: text-fig. 292a, b). On the basis of the relatively wider male pleon (assuming the figures are accurate), his material is unlikely to be T. denticarpes or T. yui as recognised here which has a proportionately narrow structure ( Figs. 29B , 32I ). Sakai (1939: 572) also describes that “the wrist [carpus of the cheliped] has an obtuse tooth at inner angle” indicating that it does not have a long or stout tooth, a feature of T. denticarpes . On the basis of the available data, Sakai’s records of “ T. canaliculata ” are possibly this species, although it cannot be discounted that they are T. decrescens s. str. as well. His material will need to be reexamined but is provisionally left in T. canaliculatus . FIGURE 12 . Typhlocarcinops canaliculatus Rathbun, 1909 , female (5.8 × 4.2 mm) (ZRC 1995.0374), Singapore. A, overall habitus; B, dorsal view of carapace; C, anterior thoracic sternum and pleon; D, sternopleonal cavity and vulvae. FIGURE 13 . Typhlocarcinops canaliculatus Rathbun, 1909 . A–G, male (5.5 × 4.2 mm) (ZRC 1995.0374), Singapore; H–M, male (8.6 × 6.5 mm) (ZRC 1985.1385), Singapore. A, frontal view showing orbit, epistome, antenna and antennule; B, left third maxilliped; C, H, male pleon; D, I, left G1 (ventral view); E, J, left G1 (dorsal view); F, K, distal part of left G1 (ventral view); G, L, distal part of left G1 (dorsal view); M, left G2. Scales: A–C, H = 1.0 mm; D, E, I, J, M = 0.5 mm; F, G, K, L = 0.25 mm. FIGURE 14 . Typhlocarcinops canaliculatus Rathbun, 1909 . A–E, male (8.7 × 6.6 mm) (ZRC 1984.7749), Phuket; F–J, male (13.2 × 10.5 mm) (ZRC 2018.0696), Hong Kong. A, right third maxilliped; B, right G1 (ventral view); C, right G1 (dorsal view); D, distal part of right G1 (ventral view); E, distal part of right G1 (dorsal view); F, left third maxilliped (dactylus missing); G, male pleon; H, left G1 (ventral view); I, left G1 (dorsal view); J, distal part of left G1 (ventral view); K, distal part of left G1 (dorsal view). Scales: A, B, F = 1.0 mm; B–E, H–K = 0.5 mm. FIGURE 15 . Typhlocarcinops canaliculatus Rathbun, 1909 , A–D, lectotype male (6.5 × 5.3 mm) of T. gallardoi Serène, 1964 (ZMUC), Java Sea; H, paralectotype female (6.3 × 5.0 mm) of of T. gallardoi Serène, 1964 (ZMUC), Makassar. A, overall habitus; B, left third maxilliped; C, D, male pleon; E, left G1 (dorsal view); F, left G1 (ventral view); DG, distal part of left G1 (ventral view); H, female pleon. Scales: B–F, H = 1.0 mm; G = 0.2 mm. B–E, G, H after Serène (1964 : fig. 11); A, D, F after Türkay (1986 : text figures 56, 57, pl. 3 fig. 13). Type locality . Gulf of Siam , Thailand . Distribution . Gulf of Siam , Thailand ; Singapore ; western Indonesia and Hong Kong . At depths of 9–14 m on soft mud and sediment.