The gekkonid lizard Cyrtodactylus intermedius was formerly considered to be a single widespread species in hilly areas across eastern Thailand through southern Vietnam but has recently been partitioned into a complex of 12 nominal species across its range. A population belonging to the C. intermedius group was recently found in an isolated limestone karst block in Kampot Province in southwestern Cambodia, part of which lies within the recently designated Phnom Preah Kuhear Loung Natural Heritage Site. Comparisons of morphometric, meristic, qualitative morphological and color pattern data, as well as a molecular analysis using the mitochondrial ND2 gene, revealed that this population differs from all other named members of the C. intermedius group, and so is described here as a new species. The karst-dwelling C. regicavernicolus sp. nov. was recovered as the sister species to C. laangensis, the most geographically proximate member of the complex and one that is also restricted to a small limestone karst habitat.
With 90 recognized species, kukri snakes in the genus Oligodon Fitzinger constitute the second largest snake radiation in the world. Oligodon species are collectively distributed across the Asian continent and possess several ecological and morphological attributes that are unique amongst other snakes. Despite their high levels of species richness, evolutionary relationships within Oligodon are poorly understood due to a limited number of samples and genetic markers available in earlier phylogenies. In this study, we assembled the largest molecular dataset of Oligodon to date, which we use to assess the systematics and biogeography of the entire genus. Based on a combination of maximum likelihood and Bayesian phylogenies using fragments of three mitochondrial genes (12 s, 16 s, CytB) and three nuclear genes (Rag1, C-mos, BDNF), we identify eight deeply divergent clades within Oligodon, of which only two correspond with species groupings that were recognized by previous morphological classifications. Four species delimitation methods employed on the mitochondrial portion of the dataset resulted in dramatically divergent estimations of molecular operational taxonomic units (mOTUs). When combined, all four methods support the existence of unrecognized species-level lineages, but also indicate that several other Oligodon species are poorly differentiated genetically and require additional integrative taxonomic research to properly resolve. Based on divergence dating, we demonstrate that Oligodon began to diversify during the early Neogene and hypothesize that the most recent common ancestor of the genus originated in mainland Southeast Asia. We conclude by recognizing eight phylogenetically defined species groups and identify sampling gaps that require further investigation once new data becomes available. This study contributes to a greater understanding of snake evolution on the Asian continent and acts as a baseline for future studies of this speciose genus.