A new species of the genus Achalinus (Squamata: Xenodermidae) from Ningshan County, Shaanxi Province, China.

A new species of odd-scaled snake in the genus Achalinus is described from Ningshan County, Shaanxi Province, China, based on seven female specimens. Morphologically, the new species can be distinguished from its congeners by the following combination of characters: (1) dorsum iridescent and uniformly dark brown in preservative, longitudinal vertebral line absent; (2) light brown beneath; (3) dotted black streak in the middle of the subcaudals absent; (4) tail length relatively short, TaL/ToL 12-16%, in females; (5) fewer subcaudals, 41-46 in females; (6) dorsal scales 23 rows throughout, strongly keeled; the outer-most rows on both sides are also keeled and slightly enlarged; (7) one loreal; (8) internasal not fused to prefrontal; (9) suture between internasals is similar in size when compared to the suture between prefrontals; (10) preocular and postocular absent; (11) 6 supralabials; (12) 5 infralabials, the first 3 (rarely 2) touching the first pair of chin shields; (13) 3 pairs of chin shields. A phylogenetic analysis using mitochondrial gene, cytochrome c oxidase subunit 1 (CO1), showed that this new species forms a monophyletic group with strong support. In addition, the uncorrected p-distances between the new species and other known congeners ranged from 3.4% to 13.0%. The recognition of the new species increases the number of described Achalinus species to 21.