Limestone jewel: A new colourful karst-dwelling pitviper (Serpentes: Viperidae: Trimeresurus) from the poorly explored borderlands of southern peninsular Thailand

Abstract We describe a new species of pitvipers from Trang Province of Thailand, near the Thailand–Malaysian border, based on morphological and molecular (2427 bp from cyt b, ND4, and 16S rRNA mitochondrial DNA genes) lines of evidence. Morphologically, Trimeresurus ciliaris sp. nov. is distinguished from its congeners by the following combination of morphological characters: a long papillose hemipenis; first supralabial and nasal scale fused; three to four small supraocular scales; internasals not in contact; small scale between nasal and the scale formed by the fused second supralabial and loreal present; dorsal scales in 17–17–15 rows across the body; ventral scales 172–175 in males, 171 in female; subcaudal scales 59–63 in males, 61 in female, all paired; in life an emerald-green dorsum with reddish-brown bands; creamy-white venter lacking dark dots or stripes on the lateral sides of the ventrals; white vertebral spots present in both sexes on every two or three dorsal scales; dark brown spots forming discontinuous pattern present on 1–3 lateral dorsal scale rows; males with reddish-brown postocular stripe. The new species forms a distinct clade on the phylogenetic tree of the genus Trimeresurus and differs from the morphologically similar species T. venustus by a significant divergence in cytochrome b mitochondrial DNA gene sequences (p = 12.5%). The new species is currently known from a small karstic area in the Nakawan Range spanning the border of Thailand and Malaysia, in particular in limestone forests in Trang and Satun provinces (Thailand); it likely also occurs in the adjacent parts of Perlis State (Malaysia). Our study also suggests that the taxonomy of T. kanburiensis species complex requires further studies; in particular our study suggests that the status of populations from Chumphon Province of Thailand and Pulau Langkawi Island of Malaysia should be re-assessed.