Tachysurustaeniatus (Günther, 1873), a senior synonym of the congeneric species T.ondon (Shaw, 1934) (Teleostei, Bagridae) from eastern China.

Despite the current recognition of Tachysurustaeniatus and T.ondon as two separate valid species of China, neither species have been revised based on examination of their types and/or topotypical materials, nor have they genetically analyzed. In this study, examination of the holotype of T.taeniatus showed that it has a serrated anterior edge of the pectoral spine, a slightly emarginate caudal fin, and longer maxillary barbels extending beyond the base of the pectoral spine, the characters shared with specimens currently identified as T.ondon. Morphological comparisons and molecular analysis showed that specimens from mainland China, which are characterized by the three mentioned morphological features, represent a single species. According to the nomenclatural rule of priority, T.taeniatus is a senior subjective synonym of T.ondon. Within this concept, T.taeniatus is widely distributed in the lower reaches of Yangtze River and coastal rivers in Zhejiang and Fujian Province and closely related to T.aurantiacus, which is endemic to Japan. The morphological differences and species-level genetic distance between T.taeniatus and T.aurantiacus provide additional support for synonymization of T.taeniatus and T.ondon. The paper also describes ontogenetic color changes and coloration polymorphism in this species. Phylogeny of the T.aurantiacus group, to which T.taeniatus belongs, is also discussed.