Turcinoemacheilus ilamensis: A new loach species from eastern Nepal (Teleostei: Nemacheilidae)

Turcinoemacheilus ilamensis , new species, is described from the Ilam District, eastern Nepal, within the Koshi River drainage. The new species is distinguished from other congeners by the anus situated immediately anterior to anal-fin origin, absence of scales on the body, large irregular dark brown blotches and mottled patterns along the dorsal and lateral surfaces. Slightly pointed snout, incomplete lateral line with 16–25 pores, usually extends to the midpoint of area between tip of pectoral fin and dorsal-fin origin. Multivariate morphometric analyses, including principal component analysis (PCA) and hierarchical cluster analysis, confirm its distinctiveness, with T . ilamensis occupying a discrete region of morphospace without overlap with congeners. Molecular analysis of the mitochondrially encoded cytochrome c oxidase I (COI) gene supports its distinctness from congeners and resolves it as the sister lineage to Turcinoemacheilus bahai . Despite this closest affinity, a substantial evolutionary gap evidenced by deep COI divergence (∼13%) and a large Euclidean morphometric distance indicates a long period of independent evolution, likely driven by ancient allopatric isolation. T . ilamensis represents the second species of the genus recorded from Nepal and further extends the known distribution of Turcinoemacheilus within the Himalayan region.