Elthusa Schioedte and Meinert, 1884

Aneesh, Panakkool Thamban, Helna, Ameri Kottarathil, Raj, Smrithy & Kumar, Appukuttannair Biju, 2023, Description of Elthusa aquabio sp. n. (Crustacea: Isopoda: Cymothoidae), a branchial fish parasitic isopod from Indian waters, Journal of Natural History 57 (21 - 24), pp. 1193-1205 : 1194-1195

Genus Elthusa Schioedte and Meinert, 1884

Elthusa, Schioedte and Meinert 1884: 337 . – Bruce 1990: 254. – Trilles and Randall 2011: 453– 454. – Hadfield et al. 2017: 125–135. – van der Wal et al. 2019: 3 . – Aneesh et al. 2020a: 2.

Type species. Livoneca emarginata Bleeker, 1857 .

Remarks. Aneesh et al. (2020a) provided a detailed generic diagnosis based on the syntype specimen of the type species examined by J.P. Trilles and the description of the same provided by Trilles and Randall (2011). Based on the revised generic diagnosis, 13 species previously included in the genus Elthusa are currently retained in Elthusa , but as incertae sedis, as their characters do not fit the genus. The following combinations of characters distinguish the genus Elthusa : having a weakly vaulted pereion; wide pleon with all pleonites wide; antennulae shorter than or subequal in length to antennae with their bases not in contact; cephalon posterior margin that is not trilobed; coxae equal size on both sides; coxae 5–7 flat and broader than anterior coxae (2–4); coxae 6–7 equal to pereonite or extending beyond, overlapping the lateral margin of pleonites; mandible palp slender, article 3 or 2 and 3 with distolateral spines setae; pereopods with relatively short dactylus; uropods short, not reaching the posterior margin of pleotelson. For a detailed comparison of Elthusa with other branchial cymothoid genera, see Aneesh et al. (2020a).