Abstract:
A new species of pitviper, Trimeresurus arunachalensis sp. nov., is described based on a single specimen. It differs from all known congeners by the following combination of characters - 19:17:15 acutely keeled dorsal scale rows (except first row - keeled or smooth); overall reddish-brown coloration; white dorsolateral stripe on outer posterior edges of ventrals and sometimes first dorsal scale row; 7 supralabials; 6 - 7 scales between supraoculars; 145 ventrals; 51 paired subcaudals (excluding the terminal scale); single anal; a sharply defined canthus rostralis with the margin overhanging the loreal region; a distinctly concave rostral scale with the upper edge projecting well beyond its lower margin; an unforked, attenuate hemipenis that extends to the 8th subcaudal scale. and has no visible spines. DNA phylogenetic analysis indicates that the new species is distinct from congeners and nested well within the Trimeresurus Glade. The closest relative based on available DNA data is T. tibetanus. The new species is presently known from a single locality - Ramda, West Kameng, Arunachal Pradesh, northeastern India.