Taxonomic Reassessment of Hebius optatus (Hu & Zhao, 1966) (Squamata: Natricidae), with the Description of a New Species from Vietnam and China

<p indent="0mm">A comprehensive taxonomic reassessment of the <italic>Hebius optatus</italic> species complex, integrating molecular data and morphological data, has led to the recognition and description of a previously overlooked species from northern Vietnam and the Guangxi Zhuang Autonomous Region, China, herein described as <italic>Hebius vogeli</italic> <bold>sp. nov.</bold> Phylogenetic analyses reveal that <italic>Hebius vogeli</italic> <bold>sp. nov.</bold> is closely related to <italic>H</italic>. <italic> sauteri</italic> and <italic>H</italic>. <italic>optatus</italic> sensu stricto. Uncorrected <italic>p</italic>-distances based on cytochrome <italic>b</italic> sequences indicate a divergence of 10.74%–11.73% between <italic>Hebius vogeli</italic> <bold>sp. nov.</bold> and <italic>H</italic>. <italic>optatus</italic>. The new species differs from <italic>H</italic>. <italic>optatus</italic> by a combination of characters, including a higher number of subcaudal scales, a greater total number of ventral and subcaudal scales, and distinct ventral coloration. <italic>Hebius vogeli</italic> <bold>sp. nov.</bold> appears to be geographically restricted to northern Vietnam and the adjacent region of Guangxi Zhuang Autonomous Region, China, making its distribution allopatric from that of <italic>H</italic>. <italic> optatus</italic>. The Pearl River is hypothesized to serve as a biogeographic barrier separating the two taxa. Accordingly, we recommend the exclusion of <italic> H</italic>. <italic>optatus</italic> from the herpetofauna of Vietnam. Based on IUCN Red List criteria, we propose that <italic>Hebius vogeli</italic> <bold>sp. nov.</bold> be assessed as Least Concern (LC). Our results emphasize both the underestimated diversity within <italic>Hebius</italic> and the need for continued integrative taxonomic efforts, particularly in the Vietnam-China borderlands, where cryptic diversity remains largely unexplored.