Description of a new loach species, Yunnanilus triangulus sp. nov. (Cypriniformes, Nemacheilidae), from Yunnan, China

A new species of the genus Yunnanilus , designated Yunnanilus triangulus sp. nov. , is described from the Nanpan River in Yunnan Province, southwestern China. Nuptial males of this species are distinguished by the presence of tubercles on the caudal peduncle during the reproductive period, a feature not observed in other members of the genus. The new species is further characterized by the following unique combination of morphological characters: body scaled, smaller eyes than interorbital width, nine inner gill rakers on first gill arch, lateral head length 27.1%–30.9% SL, head width 14.3%–17.2% SL, eye diameter 19.6%–23.8% of lateral head length, and caudal peduncle depth 94.0%–130.6% of its length. Morphological and molecular evidence support the validity of this species, despite its geographic proximity to Y. polylepis . These findings underscore the ecological specialization that exists within the genus Yunnanilus and highlight the urgent need for species-specific conservation strategies, given their restricted distributions and dependence on specific habitats.