Exostoma microadiposa (Sisoridae), a New Glyptosternine Catfish from the Zayul River, South Tibet

A new species, Exostoma microadiposa sp. nov., is described based on six specimens from the Zayul River (Lohit River), a tributary of the upper Brahmaputra River in South Tibet, China. The new species is distinguished from its congeners by the following combination of characters: posterior extremity of the adipose-fin base confluent with the upper procurrent caudal-fin rays; a combination of parallel striae and rounded plaques on the anterolateral surfaces on the lips; caudal-peduncle depth 9.9–12.0% standard length; caudal-peduncle length 17.3–21.8% standard length; eye diameter 6.7–9.0% head length; interorbital distance 31.8–37.6% head length; anal-fin base length 5.7–7.5% standard length, body depth at anus 10.5–13.2% standard length; dorsal to adipose distance 14.6–17.8% standard length and tip of nasal barbels exceeding anterior edge of eye but not reaching posterior orbital margin. Molecular phylogenetic analysis supported the new species is a closely related sister species to E. tibetanum from the lower Yarlung Tsangpo River. The average genetic distance between the new species and other species within Exostoma ranges from 6.54 to 10.82% for Cyt b and 5.80 to 14.65% for COI genes, respectively. A key to the species of the genus Exostoma is provided.