Thampramon, Ng, Peter K. L. & Vidthayanon, Chavalit, 2013

Ng, Peter K. L. & Vidthayanon, Chavalit, 2013, Thampramon tonvuthi, a new genus and new species of cavernicolous crab (Crustacea: Decapoda: Brachyura: Potamidae) from Thailand, Zootaxa 3652 (2), pp. 265-276 : 265-266

Thampramon gen. nov.

Diagnosis. Carapace subquadrate, surfaces relatively smooth; anterolateral margin distinctly convex, serrated ( Figs. 1 A, 2A–C); epigastric and postorbital cristae distinct ( Figs. 1 A, 2A–C); external orbital tooth separated from anterolateral margin by a deep V-shaped cleft ( Figs. 1 A, 2A–C); median lobe of posterior margin of epistome broadly triangular ( Fig. 3 A–C); third maxilliped with relatively long ischium ( Fig. 7 A); exopod of third maxilliped relatively long, reaching beyond upper edge of ischium with long flagellum ( Fig. 7 A, B); ambulatory legs conspicuously long ( Figs. 1 A, B, 2A–C, 6A); lateral margins of male telson concave ( Fig. 4 A, D); G1 relatively slender, almost straight with pronounced dorsal flap ( Fig. 7 C, D); basal part of G2 subquadrate ( Fig. 7 E).

Etymology. The name is derived from the Thai name for the cave at the type locality, “Tham Pra” with a common suffix for potamid genera, “-mon”, from the type genus of the family, Potamon . Gender neuter.

Remarks. While Thampramon gen. nov. is superficially similar to Phaibulamon Ng, 1992 , in general appearance (especially with regards to the long ambulatory legs), the two are unlikely to be closely related. Thampramon differs in the following aspects: carapace surface relatively smooth overall ( Figs. 1 A, 2A–C) (covered with numerous small, rounded granules in Phaibulamon , cf. Ng 1992: fig. 1); external orbital tooth separated from anterolateral margin by a deep V-shaped cleft ( Figs. 1 A, 2A–C) (separated by simple notch in Phaibulamon , cf. Ng 1992: fig. 1); epigastric cristae well developed and postorbital cristae sharp ( Figs. 1 A, 2A–C) (with very low, rounded epigastric cristae, barely visible postorbital cristae in Phaibulamon , cf. Ng 1992: fig. 1); broadly triangular median lobe of the posterior margin of the epistome ( Fig. 3 A–C) (acutely triangular in Phaibulamon , cf. Ng 1992: fig. 1); proportionately longer third maxilliped ischium ( Fig. 7 A) (relatively shorter ischium in Phaibulamon , cf. Ng 1992: fig. 2A); relatively long exopod of third maxilliped extending beyond upper edge of ischium with long flagellum ( Fig. 7 A, B) (short exopod just reaching upper edge of ischium, lacking flagellum in Phaibulamon , cf. Ng 1992: fig. 2A, B); lateral margins of male telson concave ( Fig. 4 A, D) (lateral margins of male telson gently convex in Phaibulamon , cf. Ng 1992: fig. 1); G1 relatively more slender, straight, with a pronounced dorsal flap ( Fig. 7 C, D) (G1 short, stout, C-shaped, the lower dorsal flap being of a different shape in Phaibulamon , cf. Ng 1992: fig. 2C–F); and the basal part of the G2 is subquadrate ( Fig. 7 E) (basal part of G2 ovate in Phaibulamon , cf. Ng 1992: fig. 2G).

Thampramon gen. nov. most closely resembles species of Thaipotamon Ng & Naiyanetr, 1993 (see Ng & Naiyanetr 1993) from Thailand in the form of the third maxilliped, male abdomen and G1,. Thaipotamon , however, is easily separated by a carapace that is prominently and evenly inflated, the chelipeds and ambulatory legs are not elongated, the distal part of the flap on the terminal segment of the G1 does not have a cleft, and the basal segment of the G2 is ovate (cf. Ng & Naiyanetr 1993). Most significantly, the anterior male thoracic sternum (notably somite 4) of Thaipotamon is proportionately more longitudinally elongated, with the sternoabdominal cavity reaching to just the bases of the coxae of the chelipeds (cf. Ng & Naiyanetr 1993: Figs. 16C, 17C, 20C).

Thampramon gen. nov. resembles species of Tiwaripotamon Bott, 1970 , from Indo-China in the form of the carapace, third maxillipeds, long chelipeds and ambulatory legs, and male abdomen. Tiwaripotamon differs by the absence of a sulcus on the third maxilliped ischium, the anterior thoracic sternum being longitudinally more elongated, and most significantly, the G1 being gently curved with the terminal segment subcylindrical, curving upwards and without a trace of a flap (cf. Ng & Yeo 2001).

The general carapace form, long ambulatory legs, male abdomen and structure of the G1 of Thampramon gen. nov. are also similar to Nemoron Ng, 1996 , described from central Vietnam. The male thoracic sternites 2 and 3 are completely fused in Nemoron , the third maxilliped ischium lacks a sulcus and the exopod lacks a flagellum (cf. Ng 1996).

Comparative material. Phaibulamon stilipes Ng, 1992 : Holotype male (28.5 × 22.7 mm) (ZRC 1992.8325), Tham Nam Pah Khoan cave, from "K2" resurgence, Kwai Valley, Kanchanaburi Province, Thailand, coll. French Expedition Kwai 90, 18 August 1990. Nemoron nomas Ng, 1996 : Holotype male (23.7 × 20.3 mm) (ZRC 1996.94), station Viet 0 62, Phong Nha, Hang Toi, 35 m above sea level, about 300 m inside cave, Quang Binh Province, central Vietnam, coll. L. Deharveng, A. Bedos & Levet, 11 January 1995; 1 paratype female (25.4 × 21.3 mm) (ZRC 1996.95), station Viet 0 67, in forest near Cha Noi, Quang Binh Province, central Vietnam, coll. L. Deharveng, A. Bedos & Levet, 9 January 1995. Erebusa calobates Yeo & Ng, 1999: Holotype male (20.8 × 17.8 mm) (ZRC 1998.1073), Tham Tê, near Ban Na, Khammouan Province, Laos, coll. L. Deharveng & A. Bedos, 11 February 1998; 2 paratype males (20.0 × 17.4 mm; 19.9 × 17.5 mm), 1 juvenile (ZRC 1998.1074-1075), same data as holotype; 1 paratype ovigerous female (23.0 × 19.3 mm) (ZRC 1998.1076), Tham Houai Say, near Ban Khen, Khammouan Province, Laos, coll. F. Brehier, 26 February 1998. Tiwaripotamon edostilus Ng & Yeo, 2001: Holotype male (36.4 × 28.3 mm) (ZRC 2000.0096), cave at Gia Luang, Cat Ba Island, Ha Long Bay, Vietnam, coll. L. Deharveng, 28 September 1998; 1 paratype male (40.5 × 31.1 mm) (ZRC 2000.0097), same data as holotype; 1 paratype male, 1 paratype juvenile (ZRC 2000.0098-0099), cave at Thien Long, Cat Ba Island, Ha Long Bay, Vietnam, coll. L. Deharveng, 29 September 1998; 1 paratype male (34.3 × 25.6 mm) (ZRC 2000.0100), Hoa Cuong Cave in Gia Luan, 20°50’20”N 106°58’57”E, Cat Ba Island, Vietnam, coll. M. Kottelat, 25 September 1998; 1 juvenile (ZRC 2000.0101), Sung Sot Cave, Cat Ba island, Ha Long Bay, Vietnam, coll. L. Deharveng, 2 October 1998.

Figures

FIGURE 1. Thampramon tonvuthi gen. et sp. nov. Holotype male (39.7 × 31.1 mm) (NIFI CR 00062), colour in life. A, overall dorsal view; B, ventral view; C, in situ in cave.

FIGURE 3. Thampramon tonvuthi gen. et sp. nov. Frontal views of carapace. A, holotype male (39.7 × 31.1 mm) (NIFI CR 00062); B, paratype male (33.9 × 27.8 mm) (ZRC 2012.1126); C, paratype female (42.7 × 36.3 mm) (ZRC 2012.1127).

FIGURE 4. Thampramon tonvuthi gen. et sp. nov. A – C, paratype male (33.9 × 27.8 mm) (ZRC 2012.1126); D – F, holotype male (39.7 × 31.1 mm) (NIFI CR 00062). A, D, anterior thoracic sternum, abdominal somite 6 and telson; B, E, thoracic sternum and abdomen; C, F, posterior thoracic sternum and abdominal somites 1 – 3.

FIGURE 7. Thampramon tonvuthi gen. et sp. nov. Paratype male (33.9 × 27.8 mm) (ZRC 2012.1126). A, left third maxilliped; B, exopod of left third maxilliped; C, ventral view of left G 1; D, dorsal view of left G 1; E, left G 2. Scales = 2.0 mm.