Geothelphusa, Stimpson, 1858

Naruse, Tohru, Shokita, Shigemitsu & Ng, Peter K. L., 2006, A revision of the Geothelphusa leIJicerIJix species group (Crustacea: Decapoda: Brachyura: Potamidae), with descriptions of three new species, Journal of Natural History 40 (13 - 14), pp. 759-781 : 766-769

Geothelphusa grandioIJata new species

( Figures 4 , 5a , 8b )

Potamon (Geothelphusa) leυicerυix: Miyake and Minei 1965, p 377.

Geothelphusa leυicerυix: Minei 1968, p 99, Figure 11; Minei 1973, p 211, Figures 6 , 9 (C, D) (partim); Sakai 1976, p 558 (English text), 346 (Japanese text) (partim); Gima and Shokita 1980, p 9, Figures 7 , 8 ; Minei 1981, p 80, Tables 2, 3 Plate 3 (lower) (partim); Miyake 1983, p 244, plate 51; Shokita 1990, Table 2 (partim); Anonymous 1991, p 219 (partim); Suzuki and Sato 1994, p 114 (partim); Shy et al. 1994, p 784; Ng and Shokita 1995, p 3; Anonymous 1996, p 362 (partim); Shokita 1996, p 348, Photograph 1; Yoshigou 1999, p 20, Plate 1(F) (partim); Segawa 2000, p 243, Table 1, Figures 1 , 2 (partim); Shokita et al. 2002, p 446 (partim); Kasai and Naruse 2003, p 283, Figures 67B, 71, 72 (partim); Naruse 2005a, p 190 (partim); Shokita 2005b, p 56 (partim), Plate 3 (middle right).

Material examined

Holotype: one male, CL 40.5 mm, ZLKU m. 1094, Fusato, Tamagusuku Village , coll. H. Minei, 25 June 1972 . Paratypes: eight males, CL 8.7–42.7 mm, two females, CL 19.9– 34.2 mm, three juveniles, CL 9.6–12.3 mm, ZLKU m. 1094, data same as holotype ; one male, CL 43.9 mm, ZRC 2006.0075 , Taiho River, Ohgimi Village , coll. S. Shokita et al., 3 December 1994 ; one male, CL 44.8 mm, ZRC 2006.0076 , Ohkuni Forest Road, north of Iji , coll. T. Naruse, 5 July 2001 ; one male, CL 43.8 mm, RUMF-ZC-140, Yona River, Kunigami Village , coll. S. Shokita, August 1983 ; two males, CL 29.2–29.7 mm, RUMF- ZC-141, near Ishiyama, Hedo, Kunigami Village , coll. S. Shokita, Y. Fujita, T. Nagai, H. Kawaguchi and Md. S. Islam, December 1998 ; one male, CL 41.5 mm, RUMF-ZC-142, Oshi River, Ohgimi Village , coll. S. Shokita, Y. Fujita, T. Nagai, H. Kawaguchi, and Md. S. Islam, 27 December 1998 ; one female, CL 27.1 mm, RUMF-ZC-143, east of Benoki Dam reserve, Kunigami Village , T. Naruse, 27 November 2001 ; one male, CL 37.6 mm, NSMT, Ohkuni Forest Road, between Hiji and Iji , coll. T. Naruse, 5 July 2001 ; one female, CL 34.0 mm, NSMT, Ohkuni Forest Road, Kunigami Village , coll. H. Kawauchi, 8 July 2000 . Others : four males, CL 30.0– 37.1 mm, three females, CL 32.1–41.5 mm, ZLKU C20007, data same as holotype ; two males, CL 38.4–40.6 mm, one female, CL 44.0 mm, ZLKU 10987 , Mt Yanbaru-Yama, Tamagusuku Village , coll. H. Minei, 26 June 1962 ; one female, CL 35.8 mm (31 August 1961), two females, CL 40.9–43.8 mm (26 June 1962), ZLKU 11020 , Mt Yanbaru-Yama, Tamagusuku Village , coll. H. Minei ; one male, CL 35.2 mm, ZLKU C20004, Fusato, Tamagusuku Village , coll. H. Minei, 25 June 1972 ; one male, CL 45.8 mm, ZLKU 9666 , Mt Meiji-Yama , coll. Kazuo Koba, 5 August 1956 ; one female, CL 39.4 mm, ZLKU 9667 , Mt Meiji-Yama , coll. K. Koba, 5 August 1956 . Fossil material: one palm, RUMF, Chinen Village , 2001, coll. M. Moriguchi. All specimens from Okinawa Island .

Comparatiυe material

Geothelphusa tenuimanus : all specimens examined in Naruse et al. (2004a).

Description of adult

Carapace ( Figure 4a, b ) oval, strongly convex longitudinally; surface including anterolateral margin smooth, cervical groove very shallow, H-shaped gastric groove distinct, postorbital and epigastric cristae absent, postorbital and epigastric regions raised posteriorly gradually, small pit present on posterior part of external orbital angle. Front directed downwards, frontal margin cristate, not granulated; orbital margins cristate, not granulated or granulated on outer third, supraorbital margin L-shaped in dorsal view; epibranchial tooth low, demarcated by interrupted crista, low crista confluent with epibranchial tooth but separate from external orbital angle; anterolateral margin barely cristate, not granulated. Suborbital, subhepatic, and pterygostomial regions ( Figure 8b ) smooth, no granulation visible on vertical groove and epimeral sulcus. Eye with relatively small cornea, subdistal width of cornea as wide as base of peduncle in frontal view.

Chelae of large male asymmetrical in size and shape, major chela with wide, thick, and reticulated manus, movable finger long, curved, with large gape when fingers closed.

Ambulatory legs glabrous, propodi with elliptical cross-section, two longitudinal rows of spines on inner margins; dactyli with rectangular cross-section, each margin with row of spines, inner margins with short, stout, sharp spines, outer margins with short, stout, rounded spine, subdistal spine of outer dorsal margin of fourth ambulatory dactylus stout, rounded, smaller than terminal spine.

Male abdominal segments and telson triangular, telson slightly bell-shaped, reaching imaginary line joining proximal fifth of chelipedal coxae.

G1 ( Figure 4c, d ) stout; subterminal segment curving outwards, distal part wider than proximal part, with knob on outer proximal angle; synovial membrane wide; terminal segment directed outwards, subdistal margin narrower than distal margin of subterminal segment, uneven.

Variation

In one female specimen (RUMF-ZC-143, CL 27.1 mm), the carapace is relatively flatter; with frontal margin convex medially and along both outer angles; the external orbital angle and epibranchial tooth are connected by a crista; the anterolateral margin has very low granules; the anterolateral region possesses very shallow grooves, appearing rugose; the pit behind the external orbital angle is relatively shallower; and there is a row of spines present on the outer margin of the ambulatory propodi.

Colour

Geothelphusa grandioυata is maroon to olive in colour in life. Some individuals are coloured a bluish slate-grey on the cardiac region, sides of the carapace, and third maxillipeds.

Habitat

Geothelphusa grandioυata occurs near middle to upper reaches of the banks or along small swamps in submontane areas. It also digs deep burrows adjacent to areas with water seeping out. On the basis of our collections, large individuals seem to prefer burrows which have at least some water in the bottom, but medium-sized individuals (e.g. a female, RUMF-ZC- 143, CL 27.1 mm; a male, RUMF-ZC-141, CL 29.7 mm) have been obtained from totally dried burrows ( T. Naruse, unpublished data; T. Nagai, personal communication).

Distribution

Okinawa Island, the Central Ryukyu Islands, Japan.

Etymology

The species name is derived from the Latin ‘‘ grandis ’’ (for large) and ‘‘ oυatus ’’ (for ovalshaped), suggesting the large body size and the strongly swollen carapace.

Remarks

Geothelphusa grandioυata has been regarded as G. leυicerυix since Miyake and Minei (1965). However, G. grandioυata can clearly be differentiated from G. leυicerυix s. str. by its proportionately wider G1 (versus more slender in G. leυicerυix), the wider synovial membrane of the G1 (versus more slender), and the shape of the inner margin between terminal and subterminal segment of the G1 (uneven versus smooth).

A fossil of a large brachyuran manus ( Figure 5a , RUMF, palm length 28.6+ mm, palm width 23.7+ mm) was discovered in the limestone fissure sediments of the southern part of Okinawa Island, where fossils of G. tenuimanus have been collected ( Naruse et al. 2004a). The discovered manus can be identified as that of G. leυicerυix species group by its large size [versus palm length, 18.6 mm (RUMF-GF-11); palm width,18.0 mm ( MFM 142451) in G. tenuimanus ] ( Figure 5b ). Since G. grandioυata is the only member of G. leυicerυix species group known from Okinawa Island, the fossil manus is most probably that of G. grandioυata. Naruse et al. (2004a) estimated that the geological age of the fossils of G. tenuimanus was late Pleistocene.

Figures

Figure 1. Map of the Okinawa Group in East Asia.

Figure 2. Geothelphusa leυicerυix (Rathbun, 1905), holotype, USNM 20642, male, CL 48.3 mm. (a) Dorsal view; (b) frontal view of carapace; (c) ventral side of left G1; (d) dorsal side of left G1. Scale bars: 10 mm (b); 5 mm (c, d).

Figure 4. Geothelphusa grandioυata new species. (a) Dorsal view; (b) dorsal view of carapace; (c) ventral side of G1; (d) dorsal side of G1. (a) Paratype, ZRC 2006.0076, CL 44.8 mm; (b–d) holotype, ZLKU m. 1094, CL 40.5 mm. Scale bars: 10 mm (b); 5mm (c, d).

Figure 5. Fossils of Geothelphusa grandioυata new species and G. tenuimanus (Miyake and Minei, 1965). (a) Chela of G. grandioυata (RUMF, palm length 28.6+ mm, width 23.7+ mm); (b) chela of G. tenuimanus (RUMF-GF-11, palm length 18.6 mm, palm width 17.3 mm).

Figure 6. Geothelphusa kumejima new species. (a) Dorsal view; (b) dorsal view of carpace; (c) ventral side of G1; (d) dorsal side of G1; (e) G2. (a) Paratype, ZRC 2006.0077, male, CL 35.0 mm; (b–e) holotype, RUMF-ZC-144, male, CL 39.5 mm. Scale bars: 10 mm (b); 5 mm (c–e).

Figure 7. Geothelphusa iheya new species. (a) Dorsal view; (b) dorsal view of carpace; (c) ventral side of G1; (d) dorsal side of G1; (e) G2. (a) Paratype, ZRC 2006.0078, male, CL 28.7 mm; (b–e) holotype, RUMF-ZC-148, male, CL 32.6 mm. Scale bars: 10 mm (b); 1 mm (c–e).

Figure 8. Frontal view of Geothelphusa leυicerυix (Rathbun, 1898) and G. grandioυata new species. (a) Geothelphusa leυicerυix, ZRC 2006.0074, male, CL 35.3 mm; (b) G. grandioυata, paratype, ZRC 2006.0076, male, CL 44.8 mm.

Figure 9. Frontal view of Geothelphusa kumejima new species and Geothelphusa iheya new species. (a) Geothelphusa kumejima, paratype, ZRC 2006.0077, male, CL 35.0 mm; (b) G. iheya, paratype, ZRC 2006.0078, male, CL 28.7 mm.