Ayarnangra estuarius, a new genus and species of sisorid catfish from the Ayeyarwaddy Basin, Myanmar

Abstract

Ayarnangra, a new genus (type species A. estuarius new species) is described from specimens collected in strongly tidal habitats in the lower Ayeyarwaddy (Irrawaddy) basin in southwestern Mynamar. It is probably most closely related to a small group of Indo-Gangetic sisorid genera in which keratinous epidermal structures (including those formed by unicellular hook-like unculi) are greatly reduced or absent. Of these genera Ayarnangra is most similar to Nangra. External morphology of Ayarnangra differs from that of Nangra in numerous characters, viz. shorter barbels, smaller eyes, branchiostegal membranes broadly joined to isthmus, larger non-encapsulated swim bladder with a huge tympanum, serrae on dorsal fin spine, only 5-6 pectoral fin rays, 15-16 anal fin rays, and 8/8 principal caudal fin rays. Osteologically Ayarnangra differs from Nangra in having posterior median cranial fontanel very small or entirely closed in adults, posterolateral cranial fontanelles absent, mesethmoid bone not greatly expanded, maxillary bones not firmly united to mesthmoid bone, an accessory or lateral maxillary tooth patch free of the maxillary bone, no palatal teeth, and 16+22-23=38-39 vertebrae (postabdominal notably more numerous than abdominal vertebrae). Gogangra new name is proposed as a replacement name for the Indo-Gangetic sisorid genus Gangra Roberts and Ferraris 1998 (preoccupied by Gangra Walker 1862 in Lepidoptera). The only known species of Gogangra is G. viridescens (Hamilton 1822).