Etmopterus bulbosus, a new lanternshark (Squaliformes: Etmopteridae) from the southwestern Indian Ocean

A new species of lanternshark, Etmopterus bulbosus n. sp., is described from waters off Mauritius in the southwestern Indian Ocean. The new species is assigned to the ‘Etmopterus pusillus’ clade due to it possessing distinct lateral flank markings comprising a short, thick anterior branch and a truncated posterior branch. The new species can be distinguished from all other members of the E. pusillus clade by a combination of a large bulbous snout, a distinct patch of enlarged thorn-like denticles extending posteriorly from above the pectoral-fin axil to slightly beyond the first-dorsal-fin free-rear tip, and the shape of the flank and tail markings. Etmopterus sentosus from off East Africa and Madagascar is similar, but lacks a bulbous snout, has two or three linear rows of enlarged dermal denticles above the pectoral-fin axil, and different shaped flank and tail markings. The new species is known from a single specimen collected between 400–500 m depth from a mesopelagic trawl. Molecular analysis reveals that the new species diverges from available sequences of known congeners by a minimum of 10.29% in the COI mtDNA sequence, supporting the taxonomic distinction of E. bulbosus from other members of the E. pusillus clade.