Description of a new lanternshark species from the South China Sea, with additional description of<i> Etmopterus</i><i> sheikoi</i> from Taiwanese waters (Squaliformes: Etmopteridae)

Abstract

A new species of the lanternshark genus Etmopterus Rafinesque, 1810 is described based on 23 specimens collected from the South China Sea. The new species, Etmopterus lii, being assigned to the E. lucifer group, differs from all other congeners, except E. sheikoi, by having a combination of the following morphological characters: dermal denticles frustum-shaped, giving a smooth texture of skin; pelvic-fin flank marking consists of anterior and posterior branches; and lower-jaw teeth multicuspid in mature males. It differs from E. sheikoi by having a shorter snout, a more anterior position of second dorsal fin relative to the pelvic-fin flank marking base, a thinner posterior branch of pelvic-fin flank marking, a shorter posterior caudal-fin marking, relatively larger gill slits, fewer number of teeth, and relatively fewer vertebrae. The mean K2P distance between the two species based on NADH2 sequences is 11.0%. Etmopterus sheikoi is redescribed herein based on additional specimens collected from Taiwan. We provide the first morphological description of lower-jaw tooth of mature females, and reveal the first case of sexual dimorphism in tooth count within Squaliformes. The species-group status of E. sheikoi is discussed.