Metaplax longipes Stimpson, 1858

Metaplax longipes Stimpson, 1858 View in CoL # ( Fig. 30 View Fig )

Metaplax longipes Stimpson, 1858b: 97 View in CoL ; Koelbel 1897: 711, pl. 1(1– 4); Stimpson 1907: 99; Gee 1926: 164 [list]; Gordon 1931: 528; Shen 1940a: 236; Shih et al. 2019: 9, figs. 2D–F, 4, 7E –H; Bravo et al. 2021: tab. 2.

Macrophthalmus boteltobagoe View in CoL — Bones 1982: 691, pls. 1, 2c, d; Morton and Morton 1983: 156 [not Ma. boteltobgoe Sakai, 1939 ].

Metaplax takahasii — Davie 1992a: 352, pl. 2A; SY Lee and Leung 1999: 69.

? Metaplax longipes View in CoL — SY Lee 1993: tab. 1; SY Lee and Leung 1999: 68, pl. 10; WPW Kwok and Tang 2005: 3, figs. 5, 19a; So and Lui 2007: 36.

Taxonomy: Stimpson (1907), Shih et al. (2019).

Type: Presumably lost.

Type locality: Hong Kong.

Distribution: South China Sea and East Asia: northern Vietnam, South China, and west coast of Taiwan ( Shih et al. 2019).

Habitat: Intertidal; on mudflat along fringes of mangroves, often associated with estuarine conditions.

Remarks: See remarks under Metaplax tredecim below. Local records of “ Macrophthalmus boteltobagoe ” require some discussion. This species was reported by Bones (1982) from Tong Fuk Miu Wan, and Morton and Morton (1983) from Shui (as Shiu) Hau, both sites on of sheltered sandflats on Lantau Island. The reported habitat was very different from earlier reports of Ma. boteltobagoe sensu stricto: dwelling in burrows on rocky shores of limestone substrates, from various sites in the Ryukyus, Japan ( Kosuge 1991; Kosuge and Davie 2001), and possibly also at Lanyu Island (as Kôtôsyo), Taiwan, where the species was described ( Sakai 1939). We agree with Shih et al. (2015) that on the basis of the reported habitat, this record is not true Ma. boteltobagoe .

The illustrations of Bones’ (1982) record (pls. 1, 2c, d), in any case, substantially differ from the figures of Ma. boteltobagoe Sakai, 1939 , and Ma. holthuisi Serène, 1973 (b). Compared to figures of both species in Kosuge and Davie (2001): (1) the local specimen measured approximately 1.9 × 1.4 cm, which is substantially larger than both Macrophthalmus species (cw. generally less than 1 cm: see Kosuge and Davie 2001); (2) the extraorbital tooth in the local specimen appears truncated to squarish ( Bones 1982: pl. 2c, d; reproduced as Fig. 26A, B View Fig ), whereas in both Macrophthalmus species, it is triangular, rather protruding, and slightly to distinctly acute; and (3) in the local specimen, it is devoid of any traces of fine setae or tomentum on the inner surfaces of the fingers of the chela ( Bones 1982: fig. 2d; reproduced as Fig. 26B View Fig ). As such, this record is neither Ma. boteltobagoe nor Ma. holthuisi .

Bones’ (1982) species closely resembles Metaplax in having the cheliped and fringes of the carapace nearly naked and the ambulatory legs are markedly more slender and elongated. The anterolateral lobes of Bones’ (1982) taxon, being truncate, quadrate and not clearly protruding, actually agree with of Me. longipes , a common species along the shores of Lantau Island. We provide images of an adult male specimen of Me. longipes , size 18.2 × 13.5 mm from Tung Chung, for comparison in figure 30C, D. As such, we are confident Bones’ (1982) “ Macrophthalmus boteltobagoe ” is Me. longipes instead.

Metaplax tredecim Tweedie, 1950 View in CoL #

Metaplax tredecim View in CoL — Shih et al. 2019: 16, figs. 2J–L, 6, 7M–P; Bravo et al. 2021: tab. 2.

Taxonomy: Tweedie (1950), Shih et al. (2019). Type: Holotype ò ZRC 1971.10.13.1 ( Davie and

Nguyen 2003).

Type locality: Labuan, Borneo.

Distribution: Southeast and East Asia: northern Borneo, Vietnam, to South China ( Shih et al. 2019).

Habitat: Intertidal; on mudflat along fringes of mangroves, often on substrates of coarse sands.

Remarks: Based on published records, three Metaplax species have been reported locally: M. elegans , M. longipes , and M. takahasii ( Davie 1992a) . Recently, Shih et al. (2019) showed M. takahasii Sakai, 1939 is a junior synonym of M. longipes Stimpson, 1858 , and had been incorrectly represented as “ M. takahasii ” in Davie (1992a). The third species present was identified as M. tredecim Tweedie, 1950 . The presence in Hong Kong (South China) may mark the northern limit of this essentially Southeast Asian species.