We describe a new species of the genus Lycodon based on an adult male specimen from Thanh Hoa Province, Vietnam. Lycodon namdongensis sp. nov. is differentiated from its congeners by a combination of the following characters: dorsal scales in 17-17-15 rows, all smooth; supralabials 8; infralabials 10; one large loreal on each side, separated from the eye; cloacal single; ventral scales 218 (plus two preventral scales); subcaudals 85, paired; a total length of 723 mm; tail / total length ratio 0.205; dorsal head pattern whitish grey; dorsal surface of body with 23 narrow greyish cream bands; dorsal surface of tail with 14 cream bands; ventral surface of body mostly cream with a few small dark spots posteriorly; ventral surface of tail dark grey. Based on molecular comparisons, Lycodon namdongensis sp. nov. is recovered as a sister species to L. futsingensis with strong support values from all three analyses. The new species is at least 6.5% genetically divergent from other species within this clade as shown by a fragment of more than 1000 pbs of the mitochondrial cytochrome b. This discovery increases the number of Lycodon species known from Vietnam to 15.
Keywords: Reptilia, Lycodon, new species, karst forest, morphology, phylogeny, taxonomy, Vietnam.