Redescription of Neoeucirrhichthys maydelli (Teleostei: Cobitidae) from Brahmaputra drainage, Assam, Northeastern India

Abstract

A cobitid genus Neoeucirrhichthys, a monotypic loach under family cobitidae, was described based on a single specimen of N. maydelli from Janali River (Brahmaputra River system) at Raimona, Goalpara district, Assam. Almost after four decades an attempt was made to redescribe Neoeucirrhichthys maydelli from Mechi River, Nepal without mentioning presence of minute maxillo-mandibular rudimentary barbel at the corner of mouth. And as the samples were not from the type locality of the original description, thus, need verification and confirmation of its taxonomic status with fresh specimens collected in and around the habitat of its type species. Recent collection of specimens from Khujia River (the vicinity of type locality of type species), the northern tributary of Brahmaputra drainage, Assam have found a population of Neoeucirrhichthys maydelli which is redescribed here with additional information on its morphology, anatomy and osteology. The present study reveals the presence of a lateral extension of air bladder capsule on each side which was not seen in the illustration of original description; important osteological features like neurocranium with reduced (almost absent) anterior frontal region, posterior portion of frontal bone triangular shape, no anterior preepiphysial fontanelle, posterior fontanelle triangular shape with wide base towards posterior; total vertebrae 37–38 (18‒20 abdominal vertebrae; 18–19 caudal vertebrae), dorsal fin insertion between 14–15 and 16‒17 vertebrae, anal fin insertion between 23–24 and 25–26 vertebrae; and caudal complex with 5 hypural and gap between epural and neural arch of first preural centrum (pc-1).