A new species of green pitviper of the Trimeresurus macrops complex (Reptilia: Serpentes: Viperidae) from South Central Coastal Region of Vietnam.

We describe a new species of green pitviper from southern and central parts of coastal Vietnam based on morphological and molecular (2406 bp from cyt b, ND4, and 16S rRNA mitochondrial DNA genes) lines of evidence. Trimeresurus cyanolabris sp. nov. is distinguished from its congeners by the combination of the following morphological characters: small size, maximum known SVL of 638 mm; dorsal scales in 21 (rarely 23)-21-15 rows, moderately keeled except the outermost rows; ventral scales 166-178; subcaudal scales 52-75, all paired; hemipenis forked, calyculate, reaching the 8th subcaudal; eye bright yellow in both sexes; dorsal surface deep green lacking cross-bands; postocular white stripe missing in both sexes; ventrolateral stripe faintly present on the first few dorsal scale rows in males, absent in females; throat, chin, and lower labials in shades of blue. The new species forms a distinct clade on the phylogenetic tree of the genus Trimeresurus and differs from the morphologically similar T. rubeus by a significant divergence in cytochrome b mitochondrial DNA gene sequences (p = 6.0%). The new species is currently known from low- to mid-elevations (ca. 90-400 m a.s.l.) in tropical forests of central-southern Vietnam. This discovery further underlines the importance of this area as a local center of herpetofaunal diversity and endemism, which is under great threat of deforestation.