Branchenchelys, Tighe & Kodeeswaran, 2025

Tighe, Kenneth A. & Kodeeswaran, Paramasivam, 2025, A new genus and species of ilyophine eel (Anguilliformes: Synaphobranchidae: Ilyophinae) from the Arabian Sea, western Indian Ocean, Zootaxa 5722 (4), pp. 555-569 : 556

Branchenchelys gen. nov.

Type species: Branchenchelys megacephala sp. nov.

Diagnosis. A genus of the family Synaphobranchidae , subfamily Ilyophinae , defined by its relatively large head with very large branchial chamber supported by numerous branchiostegal rays and with hypertrophied gill filaments and the following combination of characters: large gill openings, with anterior ends close together ventrally, diverging posteriorly and dorsally; possession of enlarged, compound teeth on the vomer and intermaxillary tooth patch; no pectoral fin; lateral line pores restricted to the branchial region of the head; rim of orbital foramen formed totally of ventral extensions of the frontal bone. For other characters, see the description below of Branchenchelys megacephala , the type species by designation and monotypy.

Comparative Remarks: Branchenchelys can be distinguished from the genera Ilyophis and Meadia by the presence of compound teeth (versus only simple teeth). Branchenchelys can be distinguished from the genus Atractodenchelys by the presence of a pair of transversely oriented, enlarged compound teeth on the intermaxillary tooth patch (versus 12 or more simple teeth in an irregular tooth patch). The genera Dysommina and Linkenchelys have no teeth on the intermaxillary region while Branchenchelys has the transverse pair of enlarged compound teeth on the intermaxillary mentioned above. Most members of the genus Dysomma have vomerine and intermaxillary dentition similar to Branchenchelys . Five species in the genus Dysomma ( D. goslinei Robins & Robins, 1976 , D. longirostrum Chen & Mok, 2001 , D. melanurum Chen & Weng, 1967 , D. phukutensis Prokofiev, 2019 , and D. robinsorum Ho & Tighe, 2018 ) have no intermaxillary teeth, while Branchenchelys has the transverse pair mentioned above. All other members of the genus Dysomma have the combination of a transverse pair of compound teeth on the intermaxillary region and 3‒5 compound teeth on the vomerine region of the ethmo-vomer. Branchenchelys can be distinguished from most of these species by its relatively large head with enlarged branchial chamber, larger gill openings, and hypertrophied gill filaments. Dysomma bucephalus also has a relatively large head, large gill openings, and an enlarged branchial chamber like Branchenchelys , but can be distinguished by its nearly complete lateral line (versus lateral line pores restricted to the branchial region of the head in Branchenchelys ) and presence of a pectoral fin (versus absent in Branchenchelys ).

Etymology. The generic name Branchenchelys is derived from the Greek βράγχΙΑ, gills, and εγχελύς, eel, in recognition of the enlarged gill chamber and hypertrophied gill filaments of the type species. The gender is feminine.