Bathynomus A. Milne-Edwards, 1879

Ahyong, Shane T., 2025, The deepest known supergiant deep-sea isopod: Bathynomus wilsoni, a new species from the Sulu Sea, Philippines (Crustacea: Isopoda: Cirolanidae), Raffles Bulletin of Zoology 73, pp. 169-183 : 170

Bathynomus A. Milne-Edwards, 1879

Type species. Bathynomus giganteus A. Milne-Edwards, 1897 , by monotypy.

Remarks. Bathynomus now includes 23 named extant species, four of which occur in the western Atlantic and 19 in the Indo-West Pacific. The genus is yet to be recorded from the eastern Pacific or eastern Atlantic ( Lowry & Dempsey, 2006), and the fossil record is largely concentrated in Neogene-Paleogene strata of western Europe ( Hyžný et al., 2020), presenting a typical Tethyan distribution pattern as first articulated by Ekman (1953). Bathynomus giganteus was long thought to have a near cosmopolitan distribution but Lowry & Dempsey (2006) showed it to be a western Atlantic species, with all Indo-West Pacific records being based on other species. In the Indo-West Pacific, all species of Bathynomus occur in one or other major ocean basin; none is known to span both the Pacific and Indian oceans, despite some reports to the contrary. For instance, records of several western Pacific species of Bathynomus from Indian waters, seemingly supported by molecular data ( Sankar et al., 2011; PrasannaKumar et al., 2020) are in error, with neither the presented DNA sequences nor figures corresponding to the species reported ( Huang et al., 2022, 2024). Unfortunately, such instances serve to underestimate actual species diversity and hinder the growth in taxonomic knowledge of the genus, especially in understudied regions such as the Andaman Sea, western Indian Ocean and South China Sea where new discoveries are not only likely, but currently being made (Niel Bruce, pers. com.). This highlights the importance of careful taxonomic scrutiny and careful documentation of all newly discovered specimens of Bathynomus , particularly from unexpected or underexplored localities.