Chiromantes ryukyuanus Naruse & Ng, 2008

(Figs. 1B, 9B, 10J–L)

Sesarma haematocheir – Ortmann, 1894: 717 (part). [not Grapsus (Pachysoma) haematocheir De Haan, 1833]

Holometopus haematocheir – Stimpson, 1858: 106 (part); Stimpson, 1907: 137 (part). [not Grapsus (Pachysoma) haematocheir De Haan, 1833]

Sesarma (Holometopus) haematocheir – Sakai, 1976: 655 (part); Nagai & Nomura, 1988: 42; Kishino et al., 2001: 127; Naruse, 2005: 221. [not Grapsus (Pachysoma) haematocheir De Haan, 1833]

Chiromantes ryukyuanum [sic] Naruse & Ng, 2008: 2–12, figs. 5a, 6–9; Toyota & Seki, 2014: 189.

Material examined. Holotype: male (33.1 × 29.6 mm) (RUMF-ZC-539), Taminato, Ohgimi Village, Okinawa Island, Ryukyu Islands, Japan, coll. T. Naruse, 29 July 2007. Paratypes: 1 female (30.8 × 26.9 mm) (RUMF-ZC-540), east of Funaura Bay, Iriomote Island, coll. T. Nagai, 20 October 2005 ; 1 female (28.0 × 24.7 mm) (RUMF-ZC-541), west of Mt. Tomori, Funaura Bay, Iriomote Island, coll. T. Naruse & T. Nagai, October 2005 ; 1 female (29.0 × 25.2 mm) (RUMF-ZC-542), Iriomote Island, coll. S. Shokita, 1980s ; 1 female (33.8 × 30.2 mm) (ZRC 2007.0641), near Fukari River mangrove, Komi, Iriomote Island, coll. T. Naruse, 28 September 2002 ; 6 males (5.4–13.0 × 5.1–11.9 mm), 1 female (6.5 × 5.9 mm) (RUMF-ZC-543), Oura River, Nago City, Okinawa Island, coll. T. Maenosono, 9 June 2007 ; 1 male (34.1 × 31.3 mm) (ZRC 2007.0640), data same as holotype; 1 male (34.6 × 31.0 mm) (CBM-ZC), Kijoka, Ohgimi Village, Okinawa Island, coll. H. Kimura, 24 June 2007 ; 1 female (WMNH-Na-Cr-1131), Ohara, Iriomote Island, coll. S. Nagai, March 1982 ; 1 female (26.2 × 22.7 mm) (OMNH Ar 4809), Ura River, Takigo, Amami-Ohshima Island, coll. T. Kishino et al., 2 May 2000. All localities in Ryukyu Islands, Japan .

Diagnosis. Ambulatory legs relatively longer, more slender, distal end of merus of second ambulatory leg reaching distinctly beyond level of frontal margin when folded; row of granules on dorsal margin of cheliped dactylus distinct even in large male adults; male pleonal somite 6 relatively broader.

Colour. The carapace of adult C. ryukyuanus is green with the anterior parts marbled or uniformly red (see Naruse & Ng, 2008; Toyota & Seki, 2014).

Remarks. Naruse & Ng (2008) named the species “ Chiromantes ryukyuanum ” after the Ryukyu Islands, but they did not elaborate on its etymology. Since the gender of Chiromantes is masculine, the specific name should be amended to “ C. ryukyuanus ”.

The differences between C. ryukyuanus and C. haematocheir s. str. were discussed at length by Naruse & Ng (2008) and there is no need to elaborate on them here. The main differences are: the carapace of adult of C. ryukyuanus is green with the anterior parts marbled or uniformly red in life (versus dark green with the anterior parts and margins yellowish to red in C. haematocheir); the relatively longer and more slender ambulatory legs, with the distal end of the merus of the second ambulatory leg reaching distinctly beyond the level of the frontal margin (versus the distal end of the second ambulatory merus just reaching the frontal margin in C. haematocheir); the granules on the dorsal margin of the cheliped dactylus are distinct even in large male adults (versus barely visible or absent in C. haematocheir); and the male pleonal somite 6 is relatively broader.

As discussed by Naruse & Ng (2008), many of the old records of “ Chiromantes haematocheir ” from the various islands in the Ryukyus Chain by Stimpson (1858), Ortmann (1894), Sakai (1976), Shokita (1990), Shokita et al. (2002), and Shokita et al. (2003) are almost certainly C. ryukyuanus . Chiromantes haematocheir s. str. therefore has a distribution restricted to the mainland or larger continental islands, including Korea, the main island of Japan, mainland China and Taiwan.

Biology. According to Naruse & Ng (2008: 9), C. ryukyuanus is “found near small hills which are located just beside coastlines of bays”.

Distribution. Thus far only known from the Ryukyu Islands (Naruse & Ng, 2008).