New Species of the Genus Scaphognathops, Cyprinidae, from the Lao Mekong River System

Abstract

A new cyprinid species, Scaphognathops mekongensis, is described from the Lao Mekong and its tributaries.The new species is distinguished from its only congener, S.stejnegeri, primarily by its much wider lower jaw, less developed lower lip, broader interorbital space, fewer numbers of branched rays in the dorsal and anal fins, and more numerous gill-rakers.On the other hand, S.mekongensis agrees with S.stejnegeri in the basic formation of the snout and mouth, structures of the principal simple dorsal and anal rays, squamation, shape and arrangement of the pharyngeal teeth, number of the vertebrae, and principal body proportions.These similarities clearly indicate their close relationship, and seem sufficient to recognize the new species as congeneric with S.stejnegeri.Status of the genus Scaphognathops still remains obscure.On the basis of similarities in the features of the mouth region and simple dorsal rays, the genus appears related to the Southeast Asian genus Scaphiodonichthys.Scaphiodonichthys acanthopterus is also recorded from Laos.