A new species of the genus Calamaria H. Boie in F. Boie, 1827 (Squamata, Calamariidae) from Xishuangbanna, Yunnan Province, China.

A new species of reed snake, Calamaria synergis sp. nov., is described based on two specimens collected from Mountain Jinuo, Jinghong City, Xishuangbanna Dai Autonomous Prefecture, Yunnan Province, China. The new species is distinguished from its congeners by a unique combination of morphological characters, including eight enlarged maxillary teeth; rostral higher than wide; prefrontal shorter than frontal and contacting the first two supralabials; mental not in contact with anterior chin shields; single preocular and postocular; four supralabials, with the 2^nd and 3^rd contacting the eye; five infralabials; five scales surrounding the paraparietal; ventrals 161-166; subcaudals 20-23, paired; dorsal scales reduced to six rows at the tail base and further to four rows near the terminal subcaudals; tail relatively short (6.6-9.2% of total length), abruptly tapering at the tip; dorsum blackish-brown with a distinct pale nuchal ring; two outermost dorsal scale rows pale khaki with upper margins darkened; ventral surface uniform pale khaki. Phylogenetic analysis of the mitochondrial cytochrome b gene places the new species as sister to C. andersoni and C. yunnanensis, from which it differs by an uncorrected p-distance of 8.7% and 7.9%, respectively. Calamaria synergis sp. nov. is currently known only from tropical evergreen forests of Xishuangbanna at elevations around 1,050 m asl. We propose its conservation status as Data Deficient (DD) following the IUCN Red List categories.