Abstract
A new species, Achalinushunanensissp. nov., is described from middle and western Hunan Province based on the results of molecular systematics and morphological characters. It diverges from known congeners by a significant genetic divergence (p-distance 3.2%-16.9% based on CO1 mitochondrial gene), and it can be distinguished from all known congeners by the following morphological characters: (1) all dorsal scales strongly keeled, 23 rows throughout the body, the outmost one strongly keeled and enlarged; (2) tail relatively short, TaL/TL 0.221 ~ 0.225; (3) maxillary teeth 23; (4) the suture between internasals 2 × as long as that between prefrontals; (5) loreal one, subrectangular, LorH/LorL 0.62 ~ 0.70; (6) supralabials 6, the 4(th) and 5(th) touch the eye; (7) the two anterior temporals in contact with eye; (8) ventrals 163-165, subcaudals 69-72, not paired. This raises the number of known species of Achalinus to 24.