A new species of genus Zenion Jordan & Evermann, 1896 (Zeiformes: Zeniontidae), with comments on its congeners sensu lato

Abstract

Zenion Jordan & Evermann, 1896 is currently an understudied genus. A cosmopolitan species with multiple records as “Zenion japonicum” is reidentified as a new species, named Zenion retrojaponicum n. sp., based on both morphological and molecular evidence. This new species can be morphologically distinguished from other species in terms of the lower margin of the orbit below the lower end of the pectoral-fin base, ventral-fin origin posterior to dorsal-fin origin, a thinner caudal peduncle, branchiostegal rays completely hidden in the inner side of or above the preopercular, and pored lateral-line scales less than 50. Molecularly, its mitochondrial marker, cytochrome C Oxidase subunit I gene sequence, exhibits a minimum interspecific Kimura-Two-Parameter genetic distance of 9.88% with its sister group. The real Zenion japonicum Kamohara, 1934, described by Kamohara (1934), is herein referred to as a junior synonym of Zenion hololepis (Goode & Bean, 1896). In addtion, all species that belong to or belonged to Zenion Jordan & Evermann, 1896 are discussed. Among them, for a rarely mentioned species, which was originally described as Cyttula macropus Weber, 1913 and has been reduced to junior synonym of Zenion hololepis (Goode & Bean, 1896), a new subfamily, Cyttulinae, is established with its redetermination to be under the original genus Cyttula Weber, 1913, based on both its morphological characters, including, two functional lateral lines, long ventral-fin soft rays, mouth almost vertical, profile of spinous dorsal-fin a positively skewed parabola, absent spiny ridges and absent locking mechanism, and molecular character of a minimum interspecific Kimura-Two-Parameter genetic distance of 7.56 % in multigene phylogeny among all the members under Parazenidae McAllister, 1968, and its monophyly does not disturb any other subfamilies and families, with available genetic information.