Content area
Full text
(ProQuest: ... denotes non-US-ASCII text omitted.)
INTRODUCTION
The velvet dogfish, Zameus squamulosus, was first described by Günther (1877) as Centrophorus squamulosus from a female specimen measuring 670 mm total length (TL) that was captured off Inosima (35°11'N 139°28'E), Japan, at a bottom depth of 631 m. The species was later reassigned to the genus Scymnodon Barbosa du Bocage & de Brito Capello, 1864, but was subsequently designated as the type species for the newly described genus Zameus by Jordan & Fowler (1903). Bigelow & Schroeder (1957) re-examined the issue and concluded that Zameus was a junior synonym of Scymnodon. The generic placement of this species was considered by most subsequent authors (Compagno, 1984; Yano & Tanaka, 1984; Wetherbee & Crow, 1996) to be in Scymnodon, until a detailed study by Taniuchi & Garrick (1986) concluded that it was morphologically distinct from Scymnodon, and redefined Scymnodon as a monotypical genus from the North Atlantic. These authors resurrected the genus Zameus and reassigned the species to it (Taniuchi & Garrick, 1986). Recent molecular studies have confirmed the distinctiveness of the genus Zameus from Scymnodon, and in fact, place it closer to the genus Centroselachus (Naylor et al., 2012).
The velvet dogfish is one of only two species in the genus Zameus. The other species, the Japanese velvet dogfish, Z. ichiharai, is distinguished from Z. squamulosus by the following characteristics: a shorter snout; first dorsal fin broadly rounded at its apex, posterior margin steep; pectoral fins leaf-shaped; asymmetrical median tooth; dermal denticles without transverse ridges. Coloration is uniformly black, without conspicuous markings. Zameus ichiharai is currently only known from Japan and Taiwan (Ebert et al., 2013), compared to the scattered worldwide distribution of Z. squamulosus. The taxonomic status of Z. ichiharai and its generic placement is currently under investigation (W.T. White, personal communication).
Zameus squamulosus is a poorly known somniosid shark species reported from scattered records from throughout the Atlantic, Indian, western, central and south-eastern Pacific Oceans, but to date has not been reported from the eastern North Pacific (Compagno et al., 2005; Akhilesh et al., 2013). In the Pacific, Z. squamulosus is known from off Japan, including the Kyushu-Palau Ridge, Taiwan, eastern Australia and New...