Hidden pitviper uncovered on Vietnam’s Langbian Plateau as new species

Deep in the misty montane forests of southern Vietnam, a small, stout-bodied pitviper has been quietly slipping through leaf litter under the cover of darkness, mistaken for more than a century as just another population of a widespread northern relative. Now, an integrative taxonomic study combining DNA sequencing with detailed morphological analysis has revealed that the mountain pitvipers of the Langbian Plateau are, in fact, a species entirely their own. Researchers have formally described the snake as Ovophis langbianus, the Langbian Mountain Pitviper, adding a tenth recognized species to a genus long considered a taxonomic puzzle.

The genus Ovophis, commonly known as mountain pitvipers, comprises small to medium-sized venomous snakes distributed across the highlands of East and Southeast Asia, from the Himalayas and southwestern China to Indochina, Taiwan, and the islands of the Sunda Shelf. For decades, most populations across this vast range were lumped together under a single, morphologically variable taxon, Ovophis monticola, a practice that masked what scientists now recognize as extensive hidden diversity. Over the past two decades, studies pairing molecular data with traditional anatomy have dismantled that old classification, uncovering numerous distinct species and deeply divergent lineages. Nine species were generally recognized before this latest discovery, and even that count was widely regarded as an underestimate.

One of the most confusing members of the genus has been Ovophis tonkinensis, originally described from northern Vietnam in 1934 as Trimeresurus monticola tonkinensis. Its taxonomic history reads like a revolving door: it was synonymized with O. monticola in 1937, reinstated as a subspecies in 1971, and elevated to full species status in 1981, a rank later confirmed by museum-based reviews. Today the species is considered to inhabit northern Vietnam, the Kon Tum-Gia Lai and Langbian Plateaus of the central and southern Annamite Mountains, and adjacent parts of southern China. But the idea that a single montane snake species could span more than 1,000 kilometers across several geographically isolated highlands raised immediate suspicions that cryptic diversity lurked within what was being called O. tonkinensis.

The Langbian Plateau, where the newly described species lives, is no ordinary landscape. It is one of the most important centers of endemism in mainland Indochina, an isolated montane system in the southern Annamite Mountains that has yielded a remarkable string of previously unrecognized amphibian and reptile species over the last two decades. Several reptile lineages once thought to be widespread have turned out to be complexes of geographically structured species, with the Langbian Plateau harboring deeply divergent evolutionary lineages shaped by long-term isolation of the southern highlands.

To resolve the identity of the Langbian pitvipers, the research team drew on field surveys conducted in Vietnam between 2009 and 2025, along with examinations of museum collections. Specimens were collected by hand or with snake hooks, photographed in life, and preserved according to standard protocols, with tissue samples taken for molecular work before fixation. Voucher specimens were deposited in the herpetological collections of the Joint Vietnam-Russia Tropical Science and Technology Research Center in Hanoi and the Zoological Museum of Moscow State University. All fieldwork was carried out under permits issued by Vietnamese provincial authorities, and animal handling procedures were approved by an institutional ethical committee.

The molecular centerpiece of the study was the mitochondrial cytochrome b gene, a workhorse marker in snake systematics. DNA was extracted from ethanol-preserved liver or muscle tissue, amplified by polymerase chain reaction, and sequenced in both directions on an automated capillary sequencer. The final alignment spanned 1,137 base pairs, of which 512 sites were variable and 436 were parsimony-informative. The researchers combined their newly generated sequences with homologous data from GenBank, assembling a dataset of 136 sequences representing the Langbian snakes, O. tonkinensis, and eight additional congeners, with four other pitviper species serving as outgroups. Phylogenetic trees were reconstructed using both Maximum Likelihood and Bayesian Inference, with nodal support estimated from 10,000 ultrafast bootstrap replicates and Bayesian posterior probabilities.

The results were unambiguous. All examined specimens of Ovophis tonkinensis formed a strongly supported clade, within which samples from northern Vietnam and southern China showed only limited genetic differentiation. The Langbian Plateau snakes, by contrast, formed a distinct and strongly supported lineage, recovered as the sister taxon to O. tonkinensis. Uncorrected pairwise genetic distances told the same story: the Langbian lineage differed from O. tonkinensis by 7.6 to 9.2 percent, a level of mitochondrial divergence comparable to or exceeding that reported between several currently recognized species of Ovophis. Intriguingly, one specimen from Di Linh Commune differed by 4.8 percent from the rest of the Langbian lineage, hinting at further mitochondrial structure within the plateau and underscoring the need for additional sampling and nuclear data.

Morphology corroborated the genetics. The team examined 19 preserved specimens and recorded a battery of morphometric measurements, including head length, snout length, internasal and supraocular widths, snout-vent length, and tail length, alongside meristic counts of ventral scales, subcaudals, dorsal scale rows, supralabials, and infralabials. Morphometric variables were size-corrected using an allometric adjustment before multivariate analysis. A Multiple Factor Analysis based on 15 complete specimens showed that the first two dimensions explained 63.75 percent of total variation, with the Langbian lineage and O. tonkinensis occupying two largely non-overlapping regions of morphospace. A permutational multivariate analysis of variance with 9,999 permutations confirmed that the difference between the two groups was statistically significant, with snout length, head length, supraocular width, internasal width, snout-vent length, and tail length contributing most strongly to the separation.

Ovophis langbianus can be told apart from its relatives by a distinctive combination of traits. It is smaller than O. tonkinensis, with a maximum known snout-vent length of 379 millimeters in males and 406 millimeters in females, compared with 477 and 563 millimeters respectively for its northern sister species. Males have proportionally shorter tails and fewer subcaudal scales, averaging 38.8 versus 51.1 in O. tonkinensis. The internasal scales usually touch rather than being separated by small scales, and the snake typically bears eight supralabials, with the fourth distinctly larger than the third. Its appearance is equally characteristic: the top of the head is uniformly dark brown to blackish-brown without markings, the sides of the head are heavily mottled with cream and pale orange, a pair of pale stripes runs along the neck, and the yellowish-brown to brown body carries a series of dark, butterfly-shaped or irregular blotches, with scattered whitish spots on the tail and a cream underside densely mottled with dark brown.

The new species is currently known only from the Langbian Plateau region, with records from Bidoup-Nui Ba and Chu Yang Sin National Parks and additional localities in Lam Dong, Dak Lak, and Khanh Hoa provinces, at elevations ranging from roughly 800 to 2,230 meters above sea level. It is a nocturnal snake, typically active between seven and eleven at night, moving through leaf litter near streams and occasionally sheltering under fallen logs; one female was found inside the decayed heartwood of a large log. It lives alongside other pitvipers including Trimeresurus albolabris fario, T. rubeus, and T. vogeli. No major threats have been documented, though individuals are sometimes killed by people or vehicles, and habitat loss may pose localized risks. Given its apparently broad distribution and presence in protected areas, the authors tentatively suggest a classification of Least Concern on the IUCN Red List, while noting that population data remain scarce.

The discovery carries implications well beyond a single snake. The phylogenetic analyses also identified a distinct lineage from Cao Bang Province in northern Vietnam and Guangxi in southern China, separate from both O. tonkinensis and the new species, suggesting yet another independently evolving taxon awaiting formal assessment. Vietnam now harbors four formally recognized Ovophis species, and several historical records of O. monticola from the Langbian Plateau almost certainly represent the newly described pitviper, since true members of the O. monticola complex possess paired subcaudals, a trait absent in all Langbian specimens. The study reinforces a pattern seen across many amphibian and reptile groups: the long-term geographic isolation of the southern Annamite Highlands has been a powerful engine of diversification. As researchers extend range-wide sampling across the Annamites, southern China, and the eastern Himalayas with multilocus and genomic datasets, more hidden species are likely to emerge from Asia’s montane forests.

Subject of Research: Description of a new mountain pitviper species, Ovophis langbianus, from the Langbian Plateau of southern Vietnam using molecular and morphological evidence

Article Title: A new species of the Ovophis tonkinensis species complex ( Serpentes , Viperidae ) from the Langbian Plateau, southern Vietnam

Article References: Poyarkov, N. A., Idiiatullina, S. S., Ustinova, D. A., Bragin, A. M., Le, S. X., Pawangkhanant, P., Pham, H. M., Suwannapoom, C., David, P., Vogel, G., & Nguyen, T. V. (2026). A new species of the Ovophis tonkinensis species complex (Serpentes, Viperidae) from the Langbian Plateau, southern Vietnam. Herpetozoa, 39, 325-342. https://doi.org/10.3897/herpetozoa.39.e206094

Image Credits: AI Generated

DOI: 10.3897/herpetozoa.39.e206094

Keywords: Ovophis langbianus, mountain pitvipers, Langbian Plateau, Vietnam, integrative taxonomy, cytochrome b, cryptic diversity, Annamite Mountains, Viperidae, herpetology, species delimitation, montane endemism