A new species in the <i>Pareas hamptoni</i> group (Squamata, Pareidae) from southeastern Laos

The slug-eating snakes of the <italic>Pareas hamptoni</italic> species group consist of approximately 15 species distributed across mainland Southeast Asia into northeastern India and southern China. A single specimen collected from the Dakchung Plateau in Xekong Province of southeastern Laos is shown to be molecularly and morphologically distinct from all related species in the <italic>P. hamptoni</italic> species group and is described as a new species. <italic>Pareas capitulatus</italic> <bold>sp. nov.</bold> is a smooth-scaled species having a distinctively narrow head and pattern on the nuchal region that was recovered as the sister taxon to approximately half of the members of the <italic>P. hamptoni</italic> species group. The inclusion of additional samples of <italic>P. geminatus</italic> from northern Laos demonstrated the non-monophyly of that taxon with respect to the morphologically similar <italic>P. xuelinensis</italic> and <italic>P. yunnanensis</italic>, all of which have type localities in Yunnan Province of southern China. To reconcile this taxonomic problem, <italic>P. geminatus</italic> and <italic>P. xuelinensis</italic> are treated as junior synonyms of <italic>P. yunnanensis</italic>. With these revisions, three species in the <italic>P. hamptoni</italic> species group are recognized from Laos: <italic>P. capitulatus</italic> <bold>sp. nov</bold>., <italic>P. formosensis</italic>, and <italic>P. yunnanensis</italic>. Further field surveys on the Dakchung Plateau and vicinity are needed to determine the geographic distribution and morphological variation in <italic>P. capitulatus</italic> <bold>sp. nov</bold>.