Macromedaeus crassimanus (A. Milne-Edwards, 1867)

Macromedaeus crassimanus (A. Milne-Edwards, 1867) View in CoL ( Fig. 17F View Fig )

Macromedaeus crassimanus Guinot 1968: 708 View in CoL ; 1971: 1068, Serène 1968: 75; 1984: 179, fig. 103, pl. XXV B (for complete synonymy); Ng et al. 2008: 203 [List]; Ng et al. 2017: 93 (for complete collection records from Taiwan).

Material examined: 1 ñ, NMNS 8772-57, 6.1 × 4.2, Shanfu, Liuqiu Township, Pingtung County, 4 May 2007.

Distribution: Indo-Pacific ( Guinot 1968).

Remarks: Guinot (1968) identified six species within the genus Macromedaeus : M. crassimanus (A. Milne-Edwards, 1867) , M. demani ( Odhner, 1925) , M. distinguendus (De Haan, 1835) , M. nudipes (A. Milne-Edwards, 1867) , M. quinquedentatus (Krauss, 1843) and M. voeltzkowii ( Lenz, 1905) . Recently, two additional species, M. adelus Mendoza, 2021 and M. hainanensis Yuan, Jiang and Sha, 2022 , have been described, increasing the total to eight. However, M. hainanensis appears morphological similar to M. adelus , and J.C.E. Mendoza suggested that these two species are synonymous, with M. adelus being the senior synonym according to the principle of priority ( ICZN Article 23). Mendoza based this conclusion on a careful comparison of the descriptions and illustrations provided by Yuan et al. (2022) and the type material of M. adelus . Key diagnostic features included the four broadly triangular teeth on the carapace anterolateral margin, the absence of lateral projections on the external margin of the ambulatory carpi, and the morphology of the G1 (e.g., overall shape, distal tapering, and arrangement of subdistal spiniform setae). Additionally, the female paratype of M. hainanensis resembled the female type specimens of M. adelus . Most of the type series of M. hainanensis comprised immature or subadult individuals with carapace widths of less than 10 mm, showing no significant morphological differences from similarly sized specimens of M. adelus (Hsueh, pers. comm.).

The current specimen ( Fig. 17F View Fig ) matches the key characteristics of M. crassimanus (A. Milne-Edwards, 1867) : five teeth on the anterolateral margins, a fronto-orbital width distinctly less than half the greatest carapace width, and carapace regions separated by broad, shallow furrows ( Serène 1984: 177, pl. XXV B). Macromedaeus crassimanus was first reported in Taiwan by Ho et al. (2000). This study provides the second record of this species, now from an offshore island in southwestern Taiwan.