Abstract
For decades, populations of the suck-loach genus Formosania from the Jiulongjiang River in Fujian Province, China, have been identified as F. fascicauda, a species originally described from in a separate coastal drainage basin in Fuqing County. Employing an integrative taxonomic approach combining morphological and molecular phylogenetic analyses, we demonstrate that the Jiulongjiang River population represents a distinct species, formally described here as Formosania tangi sp. nov. It is diagnosed by a combination of characters: 13 rostral barbels arranged in two rows, a distinct straight, dark, longitudinal stripe along the lateral line, and an emarginate caudal fin. Phylogenetic analyses consistently recover it as a unique evolutionary lineage showing significant genetic divergence from true F. fascicauda, with a Kimura 2-parameter distance of 4.16%. The description of F. tangi clarifies the taxonomic status of the Jiulongjiang River population and enhances our understanding of species diversity and biogeography of Formosania in the coastal drainages of southeastern China.