A new species of the Ovophis tonkinensis species complex (Serpentes, Viperidae) from the Langbian Plateau, southern Vietnam

A new species of the genus Ovophis Burger in Hoge & Romano-Hoge, 1981, is described from the Langbian Plateau, southern Vietnam, based on an integrative taxonomic approach combining morphological and molecular evidence. Ovophis langbianus sp. nov . is distinguished from its congeners by a unique combination of diagnostic morphological characters and by significant genetic divergence in the mitochondrial cytochrome b gene. Phylogenetic analyses recover the new species as the sister lineage of O. tonkinensis (Bourret), from which it differs in body proportions, head morphology, color pattern, and several meristic characters. Multivariate analyses of morphological variation further support the distinctiveness of the new species, with specimens of Ovophis langbianus sp. nov . and O. tonkinensis forming two well-separated groups in morphospace and exhibiting significant differences in centroid positions. The new species is currently known only from montane evergreen forests of the Langbian Plateau at elevations of approximately 800–2,230 m asl. The recognition of Ovophis langbianus sp. nov . further emphasizes the taxonomic complexity of the O. tonkinensis species group and, together with previous molecular evidence for a distinct Cao Bang (Vietnam)-Guangxi (China) lineage, highlights the need for a comprehensive reassessment of species boundaries within the complex.