Hongiastoma zhangbuensis, a New Species of the Subfamily Acrossocheilinae (Teleostei: Cyprinidae) from South China

<i>Hongiastoma zhangbuensis</i> sp. nov. is described from a tributary of the upper reach of the Pearl River basin based on the morphological and molecular data. It is distinguished from all known species within the subfamily Acrossocheilinae by having a combination of the following characteristics: a crescent horny sheath on the lower jaw, a less prominent lower lip limited to the corners of the mouth, a serrated posterior edge of the last simple dorsal-ray, 47-50 lateral-line scales, 9 scales above the lateral line, 16-18 circumpeduncular scales, and 16-18 pre-dorsal midline scales. The molecular phylogeny revealed that <i>H. zhangbuensis</i> sp. nov. was a sister taxon to <i>Hongiastomata argentatum</i>, with a genetic distance ranging from 10.49% to 10.68%. Together, they formed a lineage at the base of the Acrossocheilinae clade. Furthermore, the interspecific genetic distances between the new species and those of <i>Onychostoma</i> sensu lato ranged from 9.9 to 13.4%, indicating significant genetic divergence between this new species and all known species within <i>Onychostoma</i> sensu lato. Therefore, both morphological and molecular data support the recognition of this species as new.