Myopilumnus Deb, 1989

Ng, Peter K. L., Ahyong, & Shane T., 2024, Redefining Lophoplax Tesch, 1918: recognising Myopilumnus Deb, 1989, and the establishment of three new genera, Hosekia, Takedaplax, and Striacoeloma (Crustacea: Brachyura: Pilumnidae), Raffles Bulletin of Zoology 72, pp. 335-355 : 343-344

Myopilumnus Deb, 1989

Lophoplax — Tesch, 1918: 196 (part); Takeda, 1977: 120; Ng, 1987: 100 (part); Poore & Ahyong, 2023: 667, 670, 680 (part), fig. 14.112i; Trivedi et al., 2022: 596 (part); Ng & Rahayu, 2023: 429 (part). (Not Lophoplax Tesch, 1918 sensu stricto)

Myopilumnus Deb, 1989: 113 .

Type species. Myopilumnus andamanicus Deb, 1989 by monotypy. Gender of genus masculine.

Included species. Myopilumnus andamanicus Deb, 1989 ; M. pannosus ( Ng & Rahayu, 2023) , new combination; M.

sculptus ( Stimpson, 1858), new combination; M. sordidus ( Ng & Rahayu, 2023) , new combination; M. vermiculatus (A. Milne-Edwards, 1873) , new combination.

Diagnosis. Carapace subhexagonal; epigastric, protogastric, hepatic, cardio-branchial and intestino-branchial areoles prominent, smooth, glabrous; posterior carapace margin cristate, adjacent to transversely narrow but prominent intestino-branchial areole forming transverse channel extending to sub-branchial region; orbit clearly visible in dorsal view, supraorbital margin breaking general carapace outline, forming distinct concavity; eyes freely movable, ocular peduncle relatively long; lateral lobe of frontal margin not visible; anterolateral margin with 4 distinct teeth or lobes (including external orbital tooth), with additional lobe or small tubercle posteriorly; posterolateral margins distinctly converging towards posterior carapace margin. Epistome with median lobe of posterior margin obtusely triangular. Endostome not obliquely recessed posteriorly into buccal cavern, subparallel to adjacent pterygostomial surface, endostomial ridges short. Third maxilliped ischium subrectangular, length about 1.4× width. Adult male chelipeds symmetrical or almost so, not enlarged; dorsal surface of carpus with 2–4 ovate areoles; outer surface of chela densely covered with granules and setae. Ambulatory legs short, P4 longest, length about 1.3× carapace width; merus wide, stout, extensor margin cristate, outer surface with medio-longitudinal swelling or ridge; P4 merus length about 3.0–3.5× height, about half carapace width. G1 relatively stout, tip strongly recurved.

Remarks. The recognition of this group of species at the genus level requires the reinstatement of the name Myopilumnus Deb, 1989 . Deb (1989) established the genus for one new species, M. andamanicus Deb, 1989 , from the Andaman Sea. Trivedi et al. (2022) redescribed the species, known only from one female, and showed that it was morphologically closest to L. sculpta Stimpson, 1858 . As such, they placed M. andamanicus in Lophoplax , thereby also synonymising Myopilumnus under it. As concluded herein, L. sculpta and its allied species differ markedly from L. bicristata Tesch, 1918 , the type species of Lophoplax , requiring the recognition of Myopilumnus as a valid genus.

All of the species herein assigned to Myopilumnus were figured and redescribed (as species of Lophoplax ) by Trivedi et al. (2022) and Ng & Rahayu (2023).