A new species of karst-associated kukri snake (Reptilia: Squamata: Colubridae: Oligodon Fitzinger, 1826) from southern Thailand

Abstract

Abstract We describe a new species of kukri snake (Oligodon Fitzinger, 1826) from the limestone karst formations of Satun and Trang Provinces in southern Thailand. Phylogenetic analyses based on three mitochondrial DNA fragments (12S–16S ribosomal rRNA and cytochrome b) recover the new species within the Oligodon cinereus species complex, where it forms a deeply divergent yet poorly supported clade sister to Oligodon saiyok Sumontha et al., 2017 and another unnamed lineage currently referred to Oligodon cinereus (Günther, 1864) from southwest Myanmar. Morphologically, the new species is distinguished from all other members of the genus by the following combination of characters: ventral scales 189–193 with distinct lateral keeling; subcaudal scales 47–54, paired; anterior dorsal scale rows 17–19, with the reduction from 19 to 17 rows occurring above the 28th–30th ventral scale when present; maxillary teeth 8, blade-like and laterally compressed; dorsum olive–gray, plain; ventral surface white anteriorly, dark gray posteriorly; underside of tail dark gray, smeared with white. We briefly discuss the natural history and conservation status of this new species and provide observations of other kukri snakes inhabiting limestone karst habitats. Our study also incorporates genetic samples of four recently described Oligodon endemic to Thailand, all of which are recovered in the O. cinereus species complex. In agreement with previous studies, we demonstrate that species-level diversity within the O. cinereus species complex is underestimated, and additional sampling is necessary to revise this taxonomically challenging clade.