Etmopterus

[[Etmopterus]]

The deep-sea elasmobranchs commonly known as lanternsharks (Squaliformes: Etmopteridae: Etmopterus) have received an unusual level of systematic study over the past two decades (Yamakawa et al., 1986; Yano, 1988; Last et al., 2002). Sharks of the genus Etmopterus are small enigmatic sharks widely distributed in temperate and tropical waters around seamounts and along continental margins. Of the 31 recognized species in the genus, Compagno et al. (2005) reports that about one half have been described within the last 20 years. It was previously thought that the genus was comprised of a few widespread members. Deepwater trawls in the Western Pacific by both research agencies and commercial fisheries have revealed new fish fauna. Unique species of etmopterids are consistently documented, suggesting that the group contains numerous, regionally restricted sister species (Last et al., 2002).

The shape and arrangement of dermal denticles are key characteristics used to divide the genus into subgroups. The “ E. pusillus group ” is described as having denticles with low, flat, concave crowns (Springer & Burgess, 1985; Shirai & Tachikawa, 1993). The “ E. lucifer group ” was coined after Etmopterus lucifer (Yamakawa et al., 1986), a widely distributed species that is typical of the subgroup in having regular longitudinal rows of thorn-like denticles along the body. Yamakawa et al. (1986) document six members of this species complex: E. brachyurus Smith & Radcliffe, 1912; E. bullisi Bigelow & Schroeder, 1957; E. granulosus (Günther, 1880); E. lucifer Jordan & Snyder, 1902; E. molleri (Whitley, 1939); and E. villosus Gilbert, 1905. Later, E. splendidus Yano, 1988 was described making a total of seven nominal members. Western North Pacific “ E. lucifer group ” members includes four species: E. brachyurus, E. lucifer, E. molleri and E. splendidus. Compagno et al. (2005) account that all four species are reported to occur in Taiwanese waters. The remaining members of the “ E. lucifer group ” are known from Hawaii, the North Atlantic, and South America and are not considered here. During surveys of the fish markets in Taiwan, one of us (DAE) collected four specimens of a linear-denticled Etmopterus that is distinct from the other four known species. Here we describe this new species of Etmopterus, and provide a revised key for the genus in the western North Pacific.