Etmopterus westraliensis, a new species of lanternshark (Squaliformes: Etmopteridae) from Western Australia, with redescription of Etmopterus brachyurus.

Etmopterus westraliensis is described as a new species based on six specimens collected from Western Australia, eastern Indian Ocean. The new species is assigned to the Etmopterus lucifer group due to its slender, elongate anterior and posterior branches of the flank markings. It shares the following combination of morphological characters with two congeners, Etmopterus brachyurus and Etmopterus samadiae: dermal denticles hook-like, a naked area present on underside of snout, denticles present on dorsal fins in mature individuals, the origin of flank-marking base anterior to a vertical line through origin of the second dorsal fin, caudal-fin base marking thin and slender and a relatively short posterior caudal-fin marking. The new species differs from E. brachyurus in having a longer caudal-fin base marking, ventral portion of caudal-fin base marking much longer than wide, and differs from E. samadiae in having a longer mouth, different shape of the naked area on underside of snout, thinner posterior branch of flank marking, caudal-fin base marking tip tapering and more monospondylous centra. The new species is also distinguished from E. brachyurus and E. samadiae by the mean genetic distance for the NADH2 gene, that is, 0.028 and 0.040, respectively. E. brachyurus is redescribed here based on the holotype together with additional specimens collected from the northwestern Pacific.