90 urn:lsid:arphahub.com:pub:4EBD0208-8328-5D69-8C44-EC50939C0967 urn:lsid:zoobank.org:pub:52E200AF-408A-423E-8797-5BFC4FDE0F99 Herpetozoa Herpetozoa 1013-4425 2682-955X Pensoft Publishers 10.3897/herpetozoa.39.e206094 206094 Research Article Reptilia Molecular biology Systematics Zoology & Animal Biology Cenozoic Asia A new species of the Ovophis tonkinensis species complex (Serpentes, Viperidae) from the Langbian Plateau, southern Vietnam Poyarkov Nikolay A. n.poyarkov@gmail.com https://orcid.org/0000-0002-7576-2283 1 2 3 Idiiatullina Sabira S. https://orcid.org/0000-0003-1647-7754 1 Ustinova Darya A. 1 Bragin Andrey M. https://orcid.org/0000-0002-3621-9763 2 3 Le Son Xuan https://orcid.org/0009-0000-6299-7844 2 Pawangkhanant Parinya https://orcid.org/0000-0002-0947-5729 4 5 Pham Hieu Minh 6 Suwannapoom Chatmongkon chatmongkonup@gmail.com https://orcid.org/0000-0002-3342-1464 4 David Patrick https://orcid.org/0000-0001-7562-684X 7 Vogel Gernot https://orcid.org/0000-0002-4542-518X 8 Nguyen Tan Van tan.sifasv@gmail.com https://orcid.org/0000-0001-5413-968X 9 10 Department of Vertebrate Zoology, Lomonosov Moscow State University, Leninskiye Gory, GSP–1, Moscow 119234, Russia Division of Fishery, School of Agriculture and Natural Resources, University of Phayao Phayao Thailand https://ror.org/00a5mh069 Joint Vietnam-Russia Tropical Science and Technology Research Center, Nghia Do, Hanoi 122000, Vietnam Department of Vertebrate Zoology, Lomonosov Moscow State University Moscow Russia https://ror.org/010pmpe69 A. N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Leninskiy Prospekt 33, Moscow 119071, Russia Reptiles et Amphibiens, UMR 7205 OSEB, Département évolution et Systématique, CP 30, Muséum National d’Histoire Naturelle Paris France https://ror.org/03wkt5x30 Division of Fishery, School of Agriculture and Natural Resources, University of Phayao, Phayao 56000, Thailand Center for Entomology & Parasitology Research, Duy Tan University Da Nang Vietnam https://ror.org/05ezss144 Rabbit in the Moon Foundation, Suanphueng, Ratchaburi 70180, Thailand The School of Medicine & Pharmacy, Duy Tan University Da Nang Vietnam https://ror.org/05ezss144 1A Ta Quang Buu Street, Binh Dong Ward, Ho Chi Minh, Vietnam A. N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences Moscow Russia https://ror.org/05qrfxd25 Reptiles et Amphibiens, UMR 7205 OSEB, Département évolution et Systématique, CP 30, Muséum National d’Histoire Naturelle, 57 rue Cuvier, F-75231 Paris Cedex 05, Paris, France Joint Vietnam-Russia Tropical Science and Technology Research Center Hanoi Vietnam https://ror.org/05qrfxd25 Society for South East Asian Herpetology, Im Sand-3, D-69115 Heidelberg, Germany Rabbit in the Moon Foundation Ratchaburi Thailand The School of Medicine & Pharmacy, Duy Tan University, Da Nang, 550000, Vietnam Unaffiliated Ho Chi Minh Vietnam Center for Entomology & Parasitology Research, Duy Tan University, Da Nang, 550000, Vietnam Society for South East Asian Herpetology Heidelberg Germany

Corresponding authors: Nikolay A. Poyarkov (n.poyarkov@gmail.com); Tan Van Nguyen (tan.sifasv@gmail.com); Chatmongkon Suwannapoom (chatmongkonup@gmail.com)

Academic editor: Arthur Tiutenko

 2026 25 08 2026 39 325 342 13233FEB-9D68-5857-B22A-BF76216807C1 75E8D056-14D2-4839-BD04-AE8CD7C239D6 30 06 2026 07 08 2026 Nikolay A. Poyarkov, Sabira S. Idiiatullina, Darya A. Ustinova, Andrey M. Bragin, Son Xuan Le, Parinya Pawangkhanant, Hieu Minh Pham, Chatmongkon Suwannapoom, Patrick David, Gernot Vogel, Tan Van Nguyen This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. https://zoobank.org/75E8D056-14D2-4839-BD04-AE8CD7C239D6

A new species of the genus Ovophis Burger in Hoge & Romano-Hoge, 1981, is described from the Langbian Plateau, southern Vietnam, based on an integrative taxonomic approach combining morphological and molecular evidence. Ovophis langbianussp. nov. is distinguished from its congeners by a unique combination of diagnostic morphological characters and by significant genetic divergence in the mitochondrial cytochrome b gene. Phylogenetic analyses recover the new species as the sister lineage of O. tonkinensis (Bourret), from which it differs in body proportions, head morphology, color pattern, and several meristic characters. Multivariate analyses of morphological variation further support the distinctiveness of the new species, with specimens of Ovophis langbianussp. nov. and O. tonkinensis forming two well-separated groups in morphospace and exhibiting significant differences in centroid positions. The new species is currently known only from montane evergreen forests of the Langbian Plateau at elevations of approximately 800–2,230 m asl. The recognition of Ovophis langbianussp. nov. further emphasizes the taxonomic complexity of the O. tonkinensis species group and, together with previous molecular evidence for a distinct Cao Bang (Vietnam)-Guangxi (China) lineage, highlights the need for a comprehensive reassessment of species boundaries within the complex.

 Biogeography molecular phylogeny morphology mtDNA Ovophis langbianus sp. nov. southern Annamite Mountains systematics Introduction

The mountain pitvipers of the genus Ovophis Burger in Hoge & Romano-Hoge, 1981, are a group of small- to medium-sized crotaline snakes distributed across montane regions of East and Southeast Asia, ranging from the Himalayas and southwestern China to Indochina, Taiwan Island, and the Sunda Shelf islands (Malhotra et al. 2011; David et al. 2023). Historically, most populations of Ovophis were referred to the widespread and morphologically variable taxon Ovophis monticola (Günther, 1864), resulting in a complex and often controversial taxonomic history. During the last two decades, integrative taxonomic studies combining molecular and morphological data have revealed extensive cryptic diversity within the genus, leading to the recognition of numerous distinct species and deeply divergent lineages across its historically known distributional range (e.g., Zeng et al. 2023; Qiu et al. 2024; Liu et al. 2025; Liao et al. 2026). Species of Ovophis are generally characterized by the following combination of morphological traits: body coloration usually tan, yellowish brown, grayish brown, reddish brown, or brown, with large contrasting blotches that vary in color and shape among species; dorsal surface of the head usually darker than or distinctly contrasting with the body coloration; 23 or 25 (rarely 21 or 27) dorsal scale rows at midbody, smooth or only weakly keeled; first supralabial separated from the nasal; second supralabial bordering or not bordering the loreal pit; usually eight or nine supralabials; internasals generally separated from each other by one or two scales; usually 130–160 ventral scales; 30–65 subcaudals, either paired or single; and a short to moderately long tail, with a tail length to total length ratio ranging from 0.120 to 0.205 (Hoge and Romano-Hoge 1981; David et al. 2023). At present, nine species are generally recognized within the genus, although its diversity is still considered underestimated (Liao et al. 2026).

Among the currently recognized members of the genus, Ovophis tonkinensis (Bourret, 1934) remains one of the least understood taxa in terms of geographic variation and species boundaries. Originally described from northern Vietnam as Trimeresurus monticola tonkinensis Bourret, 1934, this taxon experienced a complex taxonomic history. Bourret (1937) subsequently synonymized it with Ovophis monticola, whereas Burger (1971) later reinstated it as a subspecies of O. monticola. Hoge & Romano-Hoge (1981) subsequently elevated it to full species status. Based on the examination of museum material, David and Ineich (1999) and David (2001) also recognized O. tonkinensis as a valid species. Based on Malhotra et al. (2011) and subsequent studies, O. tonkinensis is now widely recognized as a valid species.

At present, Ovophis tonkinensis is considered to occur in northern Vietnam, on the Kon Tum-Gia Lai and Langbian Plateaus in the central and southern Annamite (Truong Son) Mountains, respectively, and in adjacent regions of southern China (e.g., Malhotra et al. 2011; Nguyen and Poyarkov 2020; Poyarkov et al. 2023; Liao et al. 2026, see Fig. 1). However, most of these records are based primarily on specimens exhibiting a limited set of diagnostic morphological features traditionally associated with O. tonkinensis, particularly a fourth supralabial distinctly larger than the third and the presence of single subcaudal scales (David 2001; Fong et al. 2017; Liao et al. 2026). On this basis, populations from the Langbian Plateau in Lam Dong Province, southern Vietnam, have also been referred to O. tonkinensis (Nguyen & Poyarkov, 2020). Nevertheless, the occurrence of a montane species across several geographically isolated regions spanning more than 1,000 km raises questions regarding the taxonomic identity of these southern populations and suggests that cryptic diversity may exist within O. tonkinensis as currently understood.

10.3897/herpetozoa.39.e206094.figure1 8F3D7DCD-1340-5DDD-AB6D-55164A5E36F5

Distribution of the members of the Ovophis tonkinensis species complex. Notes: numbers indicate different localities where the species have been recorded (see Suppl. material 1: table S4 for locality details).

https://binary.pensoft.net/fig/1754160

The Langbian Plateau of southern Vietnam represents one of the most important centers of endemism in mainland Indochina and has long been recognized as a hotspot of biodiversity, particularly for montane amphibians and reptiles (Poyarkov et al. 2021, 2023). This isolated montane system in the southern Annamite Mountains harbors a highly distinctive herpetofauna and has yielded numerous endemic and previously unrecognized species of amphibians and reptiles during the last two decades (e.g., Bragin et al. 2025a, 2025b; Kliukin et al. 2025, 2026; Nguyen et al. 2025; Poyarkov et al. 2020, 2022, 2025a, 2025b; Hoang et al. 2026). Several reptile lineages formerly regarded as widespread have subsequently been shown to comprise complexes of geographically structured species, with the Langbian Plateau harboring deeply divergent evolutionary lineages (Bragin et al. 2025a, 2025b; Kliukin et al. 2025, 2026).

During recent field surveys and examinations of museum collections in southern Vietnam, we obtained additional specimens of Ovophis from the Langbian Plateau and compared them with geographically representative samples of O. tonkinensis from northern Vietnam, the Kon Tum-Gia Lai Plateau in central Vietnam, and southern China. Phylogenetic analyses of mitochondrial cytochrome b sequences recovered the Langbian population as a distinct and well-supported evolutionary lineage, sister to O. tonkinensis. Multivariate analyses of morphological variation likewise revealed significant differentiation between the Langbian population and populations of O. tonkinensis from northern Vietnam, the Kon Tum-Gia Lai Plateau of central Vietnam, and southern China. Based on concordant molecular and morphological evidence, we conclude that the Ovophis populations from the Langbian Plateau represent a distinct evolutionary lineage and describe it herein as a new species.

 Materials and methods Sampling

Field surveys were conducted in Vietnam between 2009 and 2025. Geographic coordinates and elevations were recorded using a Garmin GPSMAP 60CSx GPS receiver (Garmin Ltd., USA) using the WGS84 datum. Specimens were collected by hand or with snake hooks, photographed in life, and euthanized within 24 h after capture using an aqueous solution of tricaine methanesulfonate (MS-222). Specimens were fixed in 4% buffered formalin for approximately 24 h and subsequently transferred to 70% ethanol for long-term preservation. Prior to fixation, liver or muscle tissue samples were collected and preserved in 96% ethanol for molecular analyses. Voucher specimens were deposited in the herpetological collections of the Joint Vietnam–Russia Tropical Science and Technology Research Center, Hanoi, Vietnam (VRTC); and the Zoological Museum of Moscow State University, Moscow, Russia (ZMMU).

All procedures involving animal handling and specimen collection were approved by the Institutional Ethical Committee of the Joint Vietnam–Russia Tropical Science and Technology Research Center (VRTC). Fieldwork and specimen collection in Chu Yang Sin National Park (Dak Lak Province) and Bidoup-Nui Ba National Park (Lam Dong Province), were conducted under permits issued by the Forestry Department and the People’s Committees of Dak Lak, Khanh Hoa, and Lam Dong provinces, Vietnam (permit numbers: Dak Lak: No. 1567/UBND-TH, issued 06 April 2011; No. 170/TCLN-BTTN, issued 07 February 2013; Khanh Hoa: No. 522/SngV-TTDN&HTQT, issued 13 June 2013; No. 831/TCLN-BTTN, issued 05 June 2013; Lam Dong: No. 5832/UBND-LN, issued 22 October 2012; No. 1169/UBND-NV4, issued 17 May 2022; No. 54/VP-NV4, issued 21 January 2025).

 DNA extraction, amplification, and sequencing

Total genomic DNA was extracted from ethanol-preserved liver or muscle tissue using standard phenol–chloroform extraction protocols (Sambrook et al. 1989), followed by isopropanol precipitation. DNA concentration and quality were assessed using a NanoDrop 2000 spectrophotometer (Thermo Scientific, USA), and DNA extracts were diluted to approximately 100 ng/μL. A fragment of the mitochondrial cytochrome b (cyt b) gene was amplified using primers H14910 (5'- GACCTGTGATMTGAAAAACCAYCGTT-3') and THRSN2 (5'- CTTTGGTTTACAAGAACAATGCTTTA-3') following Burbrink et al. (2000). Polymerase chain reaction (PCR) amplifications were carried out in 20 μL reaction volumes containing approximately 50 ng genomic DNA, 10 pmol of each primer, 15 nmol of each dNTP, 50 nmol MgCl2, standard PCR buffer, and 1 U Taq DNA polymerase. Amplification conditions consisted of an initial denaturation step at 94 °C for 3 min, followed by 35 cycles of denaturation at 94 °C for 30 s, annealing at 52 °C for 40 s, and extension at 72 °C for 90 s, with a final extension at 72 °C for 10 min. PCR products were visualized on agarose gels stained with ethidium bromide and purified using Diatom DNA PCR Clean-Up kit (Isogene, Russia). Purified PCR products were sequenced in both directions using the same primers as for amplification. Sequencing reactions were performed on an ABI 3730xl automated DNA sequencer (Applied Biosystems, USA) at Evrogen Inc., Moscow, Russia.

 Molecular phylogenetic analyses

To infer phylogenetic relationships within Ovophis, newly generated cyt b sequences were analyzed together with homologous sequences of Ovophis species available from GenBank. The final dataset included 136 sequences representing Ovophis sp. from Langbian Plateau, O. tonkinensis, and eight additional congeners. Sequences of Gloydius brevicaudus (Stejneger, 1907), Protobothrops mucrosquamatus (Cantor, 1839), Trimeresurus stejnegeri Schmidt, 1925, and Tropidolaemus wagleri (Boie, 1827) were selected as outgroups. Voucher information, localities, and GenBank accession numbers are provided in Suppl. material 1: table SS1.

Sequences were initially aligned using MAFFT v.7 (Katoh et al. 2019) under default settings and subsequently checked manually in BioEdit v.7.0.5.2 (Hall 1999). Protein-coding sequences were translated into amino acids to verify the absence of stop codons or pseudogenes. Uncorrected pairwise genetic distances (p-distances) were calculated in MEGA v.6.0 (Tamura et al. 2013) using pairwise deletion of missing data. The best-fit partitioning scheme and substitution models were selected using PartitionFinder v.2.1.1 (Lanfear et al. 2012) under the Akaike Information Criterion (AIC). The selected models were GTR+I+G for the first codon position, GTR+I for the second codon position, and GTR+G for the third codon position of the cyt b gene.

Phylogenetic relationships were reconstructed using Maximum Likelihood (ML) and Bayesian Inference (BI) approaches. ML analyses were conducted in IQ-TREE v.2 (Minh et al. 2020) with nodal support estimated using 10,000 ultrafast bootstrap replicates (UFBS). Bayesian analyses were performed in MrBayes v.3.2 (Ronquist et al. 2012). Two independent Markov chain Monte Carlo (MCMC) runs, each consisting of one cold and three heated chains, were conducted for 1 million generations and sampled every 1,000 generations. Convergence and stationarity were assessed in TRACER v.1.7 (Rambaut et al. 2018), ensuring effective sample size (ESS) values exceeded 200 for all parameters. The first 25% of sampled trees were discarded as burn-in. Nodes with UFBS values ≥95% and posterior probabilities (PP) ≥0.95 were considered strongly supported; UFBS values of 90%–94% and PP values of 0.90–0.94 were considered moderately supported; lower values were considered unsupported.

 Morphological analyses

A total of 19 preserved specimens representing members of the Ovophis tonkinensis species complex were examined (Suppl. material 1: table SS2). Morphological examinations included morphometric, meristic, and qualitative characters. Although not all characters proved diagnostic in the present study, all were included to facilitate future taxonomic and geographic comparisons (Vogel et al. 2023; Idiiatullina et al. 2024). Measurements were taken using digital calipers to the nearest 0.1 mm with a Mitutoyo digital caliper, except for snout–vent length (SVL), tail length (TaL), and total length (TL), which were measured to the nearest 1 millimeter using a measuring tape. Qualitative characters, including head and body scalation, were examined under a Nikon SMZ745T stereomicroscope.

The following morphometric variables were recorded: head length (HL), snout length (SnL), internasal width (WInN), supraocular width (WsupOc), snout-vent length (SVL), tail length (TaL), and total length (TL). Meristic characters included the numbers of ventrals (VEN), subcaudals (SC), dorsal scale rows one head length behind the head (ASR), at midbody (MSR), and one head length anterior to the cloaca (PSR), supralabials (SL-left, SL-right), infralabials (IL-left, IL-right), scales separating the internasals (InN-sep), cephalic scales counted in a transverse row between the midpoints of the supraoculars (CEP), scales between the fourth supralabial and the subocular on the left and right sides (C4SL/SubOc), scales between the junction of the fourth and fifth supralabials and the subocular on the left and right sides (C45SL/SubOc), scales from the snout tip to the supraocular (Sn-SC), and head scales counted in a longitudinal row from the posterior margin of the internasals to the posterior limit of the head at the neck (He-SC). Ventral scales were counted following Dowling (1951). The terminal scute was excluded from subcaudal counts. Dorsal scale rows were counted at one head length posterior to the head, at midbody (corresponding to one-half of the total number of ventrals), and at one head length anterior to the cloaca. Bilateral characters are presented in left/right order. Sex was determined by dissection of the ventral tail base in preserved specimens. For comparisons with congeners, we examined specimens directly whenever possible and supplemented these observations with data from the literature, including David (1995), David et al. (2023, 2024), Zeng et al. (2023), Qiu et al. (2024), Liu et al. (2025), Xu et al. (2025), and Liao et al. (2026).

To assess morphological differentiation among lineages, we analyzed a dataset comprising morphometric and meristic variables. For analyses of intraspecific variation, only morphometric and meristic characters were included, whereas interspecific comparisons additionally incorporated qualitative characters. Prior to multivariate analyses, morphometric variables were size-corrected using the allometric adjustment of Thorpe (1975), with total length (TL) used as the body-size proxy.

Multivariate analyses were performed in R v.4.4.3 (R Core Team 2026). Morphological variation was explored using Multiple Factor Analysis (MFA) implemented in the package GroupStruct2 (Grismer 2025; Chan and Grismer 2026), allowing the simultaneous analysis of morphometric and meristic datasets. Although 19 specimens were examined morphologically, four specimens (NHMUK 1921.5.4.11 of Ovophis sp. from the Langbian Plateau, and MNHN-RA-1935.0117, MNHN-RA-1938.0150, and SMNH 4096 of O. tonkinensis) were excluded from the MFA because incomplete measurements resulted in missing values unsuitable for multivariate analyses. Consequently, MFA and PERMANOVA were conducted using a dataset of 15 specimens. To test for significant differences among lineages in multivariate space, we conducted a permutational multivariate analysis of variance (PERMANOVA) using 9,999 permutations. Statistical significance was accepted at P < 0.05.

 Other abbreviations

Mt. = mountain; NP = National Park; NR = Nature Reserve; Isl. = island; asl. = above sea level.

 Museum abbreviations

CAS = California Academy of Sciences, San Francisco, California, USA; CIB = Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan, China; FMNH = Field Museum of Natural History, Chicago, Illinois, USA; GP = Guo Peng’s private collection, Yibin University, Yibin, Sichuan, China; KIZ = Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, Yunnan, China; MNHN = Muséum National d’Histoire Naturelle, Paris, France; MVZ = Museum of Vertebrate Zoology, University of California, Berkeley, California, USA; RMNH = Naturalis Biodiversity Center, Leiden, Netherlands; ROM = Royal Ontario Museum, Toronto, Ontario, Canada; SMNHC = Shanghai Museum of Natural History, Shanghai, China; VRTC = Joint Vietnam–Russia Tropical Science and Technology Research Center, Hanoi, Vietnam; ZISP = Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia; ZMMU = Zoological Museum of Moscow State University, Moscow, Russia.

 Results Sequence characteristics

The final alignment of the mitochondrial cyt b gene consisted of 1,137 bp, of which 624 sites were conserved and 512 were variable, including 436 parsimony-informative positions (data given for ingroup only). The transition/transversion ratio (R) was estimated at 10.99. Nucleotide frequencies were 28.46% A, 25.95% T, 33.18% C, and 12.41% G. Newly generated sequences were deposited in GenBank under accession numbers PZ568895–PZ568902 (see Suppl. material 1: table SS1).

 Phylogenetic relationships

The ML and BI analyses recovered trees with similar topologies that were nearly identical to those reported by Liu et al. (2025) and Liao et al. (2026) (Fig. 2). According to our mitochondrial genealogy, all examined specimens of Ovophis tonkinensis formed a strongly supported clade (100/1.0; hereafter UFBS/PP values are provided). Within this clade, samples from northern Vietnam and southern China (100/1.0) showed only limited genetic differentiation and did not exhibit geographically structured subclades. Specimens of Ovophis sp. from the Langbian Plateau of southern Vietnam formed a distinct and strongly supported lineage (100/1.0), recovered as the sister taxon to O. tonkinensis (99/1.0). Two specimens initially identified as O. cf. tonkinensis from Cao Bang Province, Vietnam (ROM 35310), and Guangxi, China (GP 2042), formed a separate lineage recovered as sister to the clade comprising O. tonkinensis and Ovophis sp. from the Langbian Plateau (100/1.0). Overall, the phylogenetic analyses recovered three well-supported mitochondrial lineages corresponding to O. tonkinensis, Ovophis sp. from the Langbian Plateau, and O. cf. tonkinensis from Cao Bang and Guangxi, with Ovophis sp. from the Langbian Plateau recovered as the sister lineage of O. tonkinensis. Within the Ovophis sp. from the Langbian Plateau clade, the specimen ZMMU Re-18512 (from Di Linh Commune, Lam Dong Province, Vietnam) formed a lineage with sister relationships to the remaining examined specimens of this clade (100/1.0; Fig. 2).

10.3897/herpetozoa.39.e206094.figure2 E9EDBB7D-DF7E-58AE-BE22-372C1FDD5355

Maximum likelihood (ML) phylogenetic tree showing the matrilineal genealogy of the genus Ovophis based on 1,137 bp of cyt b sequences. For voucher specimen information and GenBank accession numbers, see Suppl. material 1: table SS1. Numbers at the nodes correspond to MLUFBS/BIPP support values, respectively. Species symbols correspond to those provided on the map in Fig. 1. Inset photograph of Ovophis langbianus sp. nov. by P. Pawangkhanant.

https://binary.pensoft.net/fig/1754161 Genetic distances

Uncorrected pairwise genetic distances (p-distances) based on the cyt b dataset are summarized in Suppl. material 1: table S3. Among the sampled taxa and lineages of Ovophis, interspecific genetic distances ranged from 4.0% (between O. zhaoermii and O. cf. meridionalis) to 14.5% (between O. monticola and Ovophis sp. from Langbian Plateau, Vietnam). The Langbian lineage differed from O. tonkinensissensu stricto by 7.6–9.2% uncorrected p-distance and from other congeners by 11.2–14.5%. These values are comparable to, or exceed, levels of mitochondrial divergence reported between currently recognized species of Ovophis (Malhotra et al. 2011; Zeng et al. 2023; Qiu et al. 2024; Liu et al. 2025; Liao et al. 2026).

The specimen ZMMU Re-18512 from Di Linh Commune, Lam Dong Province, Vietnam, differed by 4.8% from the remaining specimens from the Langbian Plateau, whereas genetic divergence among the latter was low (mean 0.8%). This pattern suggests mitochondrial differentiation within the Langbian lineage and highlights the need for additional geographic sampling and nuclear data.

 Morphological differentiation

Morphological analyses revealed clear differentiation between the Langbian lineage and Ovophis tonkinensissensu stricto. The Multiple Factor Analysis (MFA) was based on 15 specimens with complete morphometric and meristic datasets. The first two dimensions of the MFA explained 63.75% of the total variation (Dim. 1 = 52.26%; Dim. 2 = 11.49%; Fig. 3). Specimens of the Langbian lineage and O. tonkinensis occupied two largely non-overlapping regions of morphospace. A PERMANOVA analysis detected significant differences between the centroids of the two groups (P = 0.000303). Variables contributing most strongly to the observed differentiation included snout length (SnL), head length (HL), supraocular width (WsupOc), internasal width (WInN), snout-vent length (SVL), and tail length (TaL) (Fig. 4). Several meristic characters also contributed to group separation, although their effects were less pronounced than those of morphometric variables.

10.3897/herpetozoa.39.e206094.figure3 18663C9A-5F63-58F6-9800-B17886607F43

First and second dimensions (Dim. 1 and Dim. 2) of Multiple Factor Analysis (MFA) for Ovophis langbianus sp. nov. and O. tonkinensis specimens. Dots with crosses inside indicate females, dots without crosses indicate males.

https://binary.pensoft.net/fig/1754162 10.3897/herpetozoa.39.e206094.figure4 C34CF313-7AC8-5BCB-B4FD-6301A92181A3

Visualization of the contributions of meristic (blue) and morphometric (red) traits to Dimension 1 (Dim. 1) and Dimension 2 (Dim. 2) for Ovophis langbianus sp. nov. and O. tonkinensis specimens; the dashed line indicates the expected mean contribution.

https://binary.pensoft.net/fig/1754163 Systematics

The concordant evidence from mitochondrial phylogenetic analyses and morphological comparisons supports recognition of the Langbian Plateau population as a distinct species-level lineage. This population from southern Vietnam is recovered as a well-supported monophyletic lineage sister to Ovophis tonkinensissensu stricto and is further distinguished by significant differences in morphometric and meristic characters. In addition, the level of mitochondrial divergence between the Langbian lineage and O. tonkinensis is comparable to or greater than that observed among several currently recognized species of Ovophis. Accordingly, we recognize the Langbian Plateau population as a distinct species and describe it below.

Animalia Squamata Viperidae 35DD6E29-C663-55CE-BE96-C09D4E11F8F2 Ovophis langbianus https://zoobank.org/93FFADB6-7243-4CF7-ACAC-AE0A5131999C sp. nov. Figs 5 , 6 , 7 , Tables 1 –2 , Suppl. material 1: figs S1–S3 Partial chresonymy.

Ovophis monticola (non Trimeresurus monticola Günther, 1864) — Smith (1943: 508, partim); Campden-Main (1970: 102, partim); Nguyen et al. (2009: 419, partim)

Ovophis convictus (non Ovophis convictus Stoliczka, 1870) — Poyarkov and Vasilieva (2011: 192, 214, fig. 5.30, partim).

Ovophis tonkinensis (non Ovophis tonkinensis Bourret, 1934) — Nguyen and Poyarkov (2020: 782, partim); Poyarkov et al. (2023: 388–389, partim).

 Holotype.

VRTC NAP-18223 (field tag NAP-18223), adult male, collected from evergreen montane pine forest within the Bidoup-Nui Ba National Park, Lac Duong Commune, Lam Dong Province, southern Vietnam (12.192724°N, 108.677668°E; elevation 1,510 m asl) by A.M. Bragin on 13 July 2025.

 Paratypes

(n = 5, all from Vietnam). • Lam Dong Province: Bidoup-Nui Ba NP: VRTC NAP-18224 (field tag NAP-18224), subadult female, with the same collection information as the holotype; ZMMU Re-13839 (field tag NAP-00478), adult female, collected from high-elevation elfin montane forest on Mt. Bidoup, within the Bidoup-Nui Ba NP, Lac Duong Commune (12.090903°N, 108.662195°E; elevation 2,230 m asl) by N.A. Poyarkov on 09 May 2009; Di Linh Commune: ZMMU Re-18512 (field tag NAP-12888), adult male, collected from secondary montane polydominant forest at Suoi Lanh Stream, Gung Re Village, Di Linh Commune (11.47117°N, 108.07013°E; elevation 1,190 m asl) by N.A. Poyarkov, P. Pawangkhanant, and H.M. Pham on 07 September 2022; and ZMMU Re-18511 (field tag NAP-14633), adult male collected by H.M. Pham on June 17, 2023, from the same locality as ZMMU Re-18512; • Dak Lak Province: Chu Yang Sin NP: ZMMU Re-14068 (field tag NAP-02669), adult male, collected from polydominant mixed evergreen montane forests on the slope of Mt. Chu Pan Fan, within the Chu Yang Sin NP, Bong Krang Commune (12.37557°N, 108.354057°E; elevation 1,730 m asl) by N.A. Poyarkov on 07 April 2012.

 Referred material

(n = 2, all from Vietnam). • Lam Dong Province: Sui Kat area, D’Ran Commune: NHMUK 1921.5.4.11, adult male, collected by Malcolm Smith in 1921. • Khanh Hoa Province: Hon Ba NR: ZMMU Re-15709, subadult female, collected by A.B. Vassilleva on 29 June 2018 (12.11250°N, 108.97889°E; elevation 800 m asl).

 Diagnosis.

Ovophis langbianus sp. nov. can be distinguished from all other congeners by the following combination of characters: (1) TaL/TL ratio 0.14–0.18 in males and 0.12–0.14 in females; (2) internasals usually in contact, rarely separated by one small scale; (3) second supralabial bordering loreal pit; (4) dorsal scale rows 25 (21, 23, 27)–21 (23, 25)–19 (15, 17); (5) ventrals 129–138; (6) dorsal scales strongly keeled; (7) subcaudals 36–44, all single; (8) fourth supralabial larger than third; (9) dorsal surface of head uniformly dark brown to blackish-brown, lacking distinct markings; (10) sides of head heavily mottled with cream and pale orange; (11) a pair of pale dorsolateral neck stripes present; (12) dorsum yellowish-brown to brown, with a series of dark brown to blackish-brown butterfly-shaped, subquadrate, or irregular blotches; (13) tail brown, bearing scattered whitish spots; and (14) venter cream to off-white, densely mottled with dark brown.

 Description of holotype.

Adult male (Figs 5, 6A), specimen in good condition.

10.3897/herpetozoa.39.e206094.figure5 7470059F-434A-5BC3-9FB0-0BF7E4325620

Holotype of Ovophis langbianus sp. nov. in life (VRTC NAP-18223, adult male). A. Dorsal view; B. Ventral view; C. Head in right lateral view; D. Head in left lateral view; E. Head in dorsal view; F. Head in ventral view. Photographs by A.M. Bragin.

https://binary.pensoft.net/fig/1754164 10.3897/herpetozoa.39.e206094.figure6 5E2FB168-6E48-56ED-9621-FE86F473200C

Incompletely everted hemipenes of Ovophis langbianus sp. nov. A1. General view of the hemipenes of VRTC NAP-18223 (holotype); A2. Enlarged view of the exposed distal portion of one hemipenis of the same specimen; B. Hemipenes of ZMMU Re-18511 (paratype). Photographs by A.M. Bragin (A1–A2) and N.A. Poyarkov (B). Scale bars are unavailable.

https://binary.pensoft.net/fig/1754165

Morphology. Body stout and robust; SVL 298 mm, TaL 50 mm, TL 348 mm, TaL/TL ratio 0.14. Head distinctly triangular in dorsal view, clearly differentiated from neck; HL 16.96 mm, HL/SVL ratio 0.06. Snout blunt and rounded, rostral small, trapezoidal, broader than high, barely visible from above; canthus rostralis indistinct. Eyes small; ED 2.36 mm, SnL 5.08 mm, SnL/ED ratio 2.15. Pupil vertically elliptic.

Head scalation. Loreal pit large, deep, triangular. Nostril situated within a large undivided nasal scale. First supralabial separated from nasal by a distinct suture. Second supralabial forming the anterior border of the loreal pit. Preoculars 3/3; postoculars 3/3. Subocular 1/1; subocular separated from the supralabials by one row of small scales. Loreal single. Supralabials 8/8, fourth supralabial distinctly larger than third and fifth; infralabials 10/10, first pair contacting each other behind mental, first to third in contact with chin shields; mental triangular; one pair of chin shields, meeting in midline. Internasals large, in broad medial contact, not separated by small scales. Supraoculars large, single on each side. Scales on dorsal surface of snout and interorbital region smooth, irregularly arranged; temporal and occipital scales smooth.

Body scalation. Dorsal scale rows 25–21–19, distinctly keeled except for the outermost row, which is smooth. Ventrals 130; preventrals 1. Cloacal plate entire. Subcaudals 37, all single.

Hemipenes. The hemipenes are incompletely everted in situ (Fig. 6). The exposed portions are short and stout and densely covered with spinulate calyces. Because the organs are incompletely everted, the morphology of the lobes and apical ornamentation could not be reliably assessed. In preservative, the hemipenes are pale pink to translucent white.

 Coloration in life

(Figs 5, 7A). Dorsal surface of head uniformly dark brown to blackish-brown, lacking distinct dorsal markings. Rostral region, supralabials, preocular, postocular, and temporal regions heavily ornamented with cream and pale orange spots and vermiculations, forming a conspicuous mottled pattern on the sides of the head. A pair of narrow pale cream dorsolateral stripes extends from the posterior margin of the head onto the neck. Iris dark grayish-brown with a vertically elliptical pupil. Dorsal ground coloration of body dark brown to grayish brown, with a series of large pale tan to yellowish-brown blotches, mostly butterfly-shaped to subquadrate and separated by broad dark interspaces; the blotches become smaller and less distinct posteriorly. Tail dark brown, bearing scattered cream to whitish spots. Ventral surface cream to off-white, densely mottled with dark brown blotches and speckles, forming irregular transverse markings along the body and tail; chin and throat predominantly cream with scattered dark brown markings.

10.3897/herpetozoa.39.e206094.figure7 A5AB948E-49DF-51F5-A42F-455CF01C4044

Ovophis langbianus sp. nov. in life from Langbian Plateau, Vietnam — Lam Dong Province: Bidoup-Nui Ba NP: A. VRTC NAP-18223, adult male, holotype; Di Linh Commune: B. Dorsal view of ZMMU Re-18511, adult male, paratype; C. Head in lateral view of the ZMMU Re-18511; D. ZMMU Re-18512, adult male, paratype; E. Head in lateral view of the ZMMU Re-18512; F, G. Two adult individuals, sex undetermined. Dak Lak Province: — Chu Yang Sin NP: H. ZMMU Re-14068, adult male, paratype; I. Head in dorsal view of the ZMMU Re-14068. Photographs by A.M. Bragin (A), N.A. Poyarkov (B, C, H, I), P. Pawangkhanant (D, E), and H.N.X. Nguyen (F, G).

https://binary.pensoft.net/fig/1754166 Variation

(for detailed information, see Table 1, Fig. 7). The longest known specimen is 474 mm long (SVL 406 mm, TaL 68 mm; adult female, ZMMU Re-13839); the longest known male is 463 mm long (SVL 379 mm, TaL 84 mm; ZMMU Re-14068). Ratio TaL/TL: 0.12–0.18 (0.14–0.18 in males, 0.12–0.14 in females).

Selected morphological characters of examined specimens of Ovophis langbianus sp. nov. from Langbian Plateau, southern Vietnam. Notes: M = adult male, F = adult female, SF = subadult female, H = Holotype, P = Paratype, and complete morphological data are provided in Suppl. material 1: table SS2.

Voucher number Locality Sex SVL (mm) TaL (mm) VEN SC ASR MSR PSR SL IL InN-sep CEP Sn-SC He-SC
VRTC NAP-18223 H Bidoup-Nui Ba NP, Lam Dong M 298 50 130 37 25 21 19 8/8 10/10 0 6 4 21
ZMMU Re-18512 P Di Linh, Lam Dong M 346 62 130 38 23 21 15 8/8 9/9 0 5 3 20
ZMMU Re-18511 P Di Linh, Lam Dong M 331 59 129 37 21 21 17 8/8 9/9 0 7 3 20
NHMUK 1921.5.4.11 D’Ran, Lam Dong M 371 71 131 38 23 21 17 8/8 9/9 0 6 3 18
ZMMU Re-14068 P Chu Yang Sin NP, Dak Lak M 379 84 136 44 27 25 19 8/8 9/9 0 6 4 19
ZMMU Re-13839 P Bidoup-Nui Ba NP, Lam Dong F 406 68 132 41 27 25 19 9/9 10/10 1 7 4 22
VRTC NAP-18224 P Bidoup-Nui Ba NP, Lam Dong SF 289 41 138 36 25 23 19 8/8 10/10 0 6 4 22
ZMMU Re-15709 Hon Ba NR, Khanh Hoa SF 242 32 133 37 25 25 19 9/9 10/10 0 7 4 21

Body scalation. DSR 25 (21, 23, 27)–21 (23, 25)–19 (15, 17); VEN 129–138; SC 36–44.

Head scalation. SL 8 (rarely 9); IL: 9 (rarely 10); InN-sep 0 (rarely 1); CEP 5–7; He-SC 18–22.

Coloration and pattern. Dorsal ground coloration varies from yellowish-brown to brown. The dorsal blotches are dark brown to blackish-brown and vary from butterfly-shaped to subquadrate or irregular in shape. They also vary in size, degree of fusion, and contrast with the ground coloration. The dorsal surface of the head is generally uniform dark brown to blackish-brown; however, the extent of pale mottling on the lateral surfaces of the head varies among individuals. Cream and pale orange markings on the supralabial, preocular, postocular, and temporal regions range from sparse and fragmented to extensive, forming conspicuous reticulations. The pale dorsolateral stripes on the neck are usually distinct but may vary in width and intensity. The tail bears scattered cream to whitish spots, which vary in size and prominence among specimens. Ventral coloration ranges from cream to grayish-white and is variably mottled with dark brown; the mottling may be sparse and scattered or dense, forming irregular transverse markings on the ventral surfaces of the body and tail. Live specimens generally exhibit warmer coloration, with yellowish-brown to orange-brown dorsal hues and more conspicuous cream to pale orange markings on the sides of the head than preserved specimens.

 Etymology.

The specific epithet “langbianus” is a masculine Latin adjective derived from the name of the Langbian Plateau, the broader geographic region containing the type locality and the currently known distribution of the new species. The name highlights the biogeographic isolation of the Langbian Plateau, an important center of montane endemism in Indochina. We suggest the following common names for the new species: “Langbian Mountain Pitviper” (in English), “Rắn lục núi Langbian” (in Vietnamese), “Лангбианский горный щитомордник” (Langbianskiy gornyi schitomordnik, in Russian), and “Ovophis de Langbian” (in French).

 Comparisons.

The main diagnostic characters separating Ovophis langbianus sp. nov. from its congeners are summarized in Table 2. Morphologically, Ovophis langbianus sp. nov. most closely resembles O. tonkinensis. It can be distinguished from the latter by its smaller adult body size (maximum SVL 379 mm in males and 406 mm in females vs. 477 mm in males and 563 mm in females); lower TaL/TL ratio in males (0.14–0.18 [mean 0.16] vs. 0.18–0.21 [mean 0.19]); fewer subcaudals in males (SC 37–44 [mean 38.8] vs. 47–55 [mean 51.1]); absence or rare occurrence of small scales separating the internasals (usually absent, rarely one vs. usually one or two); fewer He-SC (18–21 [mean 19.6] in males and 21–22 [mean 21.7] in females vs. 25–32 [mean 27.6] in males and 25–31 [mean 28.6] in females); fewer infralabials in males (IL 9–10 vs. 10–12); and fewer supralabials (SL 8, rarely 9 vs. 9–10).

Comparison of selected morphological characters among species of the genus Ovophis. Characters used are: (1) ASR–MSR–PSR; (2) VEN in males; (3) VEN in females; (4) SC; (5) 3rd vs. 4thSL; (6) head dorsum; (7) dorsal ground color; (8) dorsal blotches; (9) white spots on tail dorsum. Remark: n/a = not available.

Species (1) (2) (3) (4) (5)
O. langbianus sp. nov. 25 (21, 23, 27)–21 (23, 25)–19 (15, 17) 129–136 132–138 36–44, single 3rd < 4th
O. anitae 27–23–19 n/a 145 47, paired 3rd > 4th
O. convictus 25–25–18 126–132 125–140 17–31, paired 3rd > 4th
O. jenkinsi 23 (25)–21 (23, 25)–19 (17, 21) 134 138–142 40–52, paired 3rd > 4th
O. makazayazaya 25 (27, 29)–23 (25, 21)–19 (21) 131–159 133–157 34–52, paired 3rd < 4th
O. medogensis 23 (25)–23–19 138 132–136 39–49, paired 3rd > 4th
O. monticola 23 (21)–23 (21)–19 144–162 141–153 37–58, paired 3rd > 4th
O. tonkinensis 27 (25, 29, 31)–25 (23, 27)–19 (21, 23) 122–134 127–134 39–55, single 3rd < 4th
O. zayuensis 25 (27)–23–19 (17) 162–176 160–175 43–64, single 3rd > 4th
O. zhaoermii 22–21–17 146–148 145–152 46–64, paired 3rd > 4th
Species (6) (7) (8) (9) Sources
O. langbianus sp. nov. Unpatterned Yellowish-brown to brown Large butterfly-shaped, subquadrate, or irregular dark blotches Scattered This study
O. anitae Patterned Brownish-black Mostly rectangular Scattered Zeng et al. 2023
O. convictus Unpatterned Yellowish-brown Mostly rectangular Scattered Our data
O. jenkinsi Patterned Deep orange-brown or dark brownish-gray Mostly trapezoidal Scattered Qiu et al. 2024
O. makazayazaya Patterned or unpatterned Yellowish-brown or dark grey Smaller, narrow, irregular dark blotches, usually interconnected into a continuous zigzag or reticulate pattern Scattered Liao et al. 2026; our data
O. medogensis Patterned Deep blackish-brown or dark brownish Mostly butterfly-shaped irregular blotches Scattered Liao et al. 2026
O. monticola Patterned Yellowish-brown Mostly rectangular Scattered Liao et al. 2026; our data
O. tonkinensis Unpatterned Brown, tan or crimson Bearing subquadrate or irregular blotches Scattered This study
O. zayuensis Patterned or unpatterned Reddish-brown or brown Mostly trapezoidal and triangular No visible white spots Liao et al. 2026; our data
O. zhaoermii Patterned or unpatterned Brownish-black Mostly rectangular Continuous Liu et al. 2025; our data

Ovophis langbianus sp. nov. further differs from O. anitae, O. convictus, O. jenkinsi, O. monticola, O. medogensis, and O. zhaoermii by having undivided subcaudals (vs. paired or predominantly paired). It is additionally distinguished from these species by the fourth supralabial being larger than the third (vs. the third supralabial larger and taller than the fourth). The new species differs from O. makazayazaya by possessing undivided subcaudals (vs. paired or predominantly paired) and fewer supralabials (8, rarely 9 vs. 10–11, rarely 9 or 12). Ovophis langbianus sp. nov. differs from O. zayuensis, which also has undivided subcaudals, in having the fourth supralabial larger than the third (vs. the third supralabial larger and taller than the fourth), and fewer ventrals (129–136 in males, 132–138 in females vs. 162–176 in males, 160–175 in females).

 Distribution and natural history.

Ovophis langbianus sp. nov. is currently known only from the Langbian Plateau of southern Vietnam, where it has been recorded from several localities: Bidoup-Nui Ba NP as well as Di Linh and D’Ran Communes in Lam Dong Province (with additional observations from Da Lat Commune; T.V. Nguyen, pers. obs.), Chu Yang Sin NP in Dak Lak Province, and Hon Ba NR in Khanh Hoa Province (Fig. 1).

The species inhabits montane tropical evergreen forests at moderate to high elevations from 800 to 2,230 m asl. At these localities, the new species was recorded in different types of forests ranging from highly disturbed secondary montane polydominant, evergreen forests or pine forests dominated by Pinus kesiya Royle ex Gordon and P. dalatensis Ferré (family Pinaceae Lindley) at lower elevations to high-elevation elfin montane forests composed of trees from the families Fagaceae Dumort., Lauraceae Juss., and Magnoliaceae Juss., characterized by a thick leaf litter layer, numerous fallen logs, and numerous streams. Ovophis langbianus sp. nov. is a nocturnal species, typically active between 19:00 and 23:00 h. Individuals have been observed on the forest floor among leaf litter, usually in the vicinity of streams. Occasionally, specimens were found under fallen logs; the female specimen ZMMU Re-13839 was found inside the decayed heartwood of a large fallen log. Sympatric pitviper species include Trimeresurus albolabris fario (Jan, 1859), T. rubeus (Malhotra, Thorpe, Mrinalini & Stuart, 2011), and T. vogeli David, Vidal & Pauwels, 2001.

 Conservation status.

At present, no major threats have been documented for the new species. However, individuals are occasionally killed by local people because of their venomous nature or by vehicles while crossing roads (T.V. Nguyen, pers. obs.). Habitat loss and forest degradation may represent localized threats, particularly in the Di Linh Commune, Lam Dong Province, Vietnam. Because information on population size, population trends, and reproductive biology remains unavailable, a formal conservation assessment is premature. Nevertheless, given its apparently broad distribution across the Langbian Plateau and occurrence within several protected areas, we tentatively recommend that O. langbianus sp. nov. be classified as Least Concern (LC) according to the IUCN Red List Categories and Criteria (IUCN Standards and Petitions Subcommittee 2019).

 Discussion

The present study provides congruent molecular and morphological evidence for recognizing the Langbian Plateau population as a distinct species, herein described as Ovophis langbianus sp. nov. Phylogenetic analyses recovered the new species as a well-supported monophyletic lineage sister to O. tonkinensissensu stricto, while multivariate analyses revealed clear morphological differentiation between these taxa. The observed level of mitochondrial divergence is comparable to, or greater than, that reported among several currently recognized species of Ovophis (Malhotra et al. 2011; Zeng et al. 2023; Qiu et al. 2024; Liu et al. 2025; Liao et al. 2026; this study). These findings are consistent with recent studies suggesting that species diversity within Ovophis has been substantially underestimated and that several nominally widespread taxa actually comprise complexes of geographically structured evolutionary lineages. Traditionally, O. tonkinensis has been diagnosed by the presence of an enlarged fourth supralabial and predominantly undivided subcaudals (David 2001; Fong et al. 2017). However, these characters are also present in Ovophis langbianus sp. nov., suggesting that these characters may be shared by a broader lineage within the O. tonkinensis species complex rather than being diagnostic of a single taxonomic entity. Our results highlight the importance of integrative approaches combining molecular, morphometric, and meristic datasets for species delimitation in mountain pitvipers.

In addition to the newly described species, our phylogenetic analyses identified a distinct lineage comprising populations from Cao Bang Province in northern Vietnam and Guangxi Zhuang Autonomous Region in southern China. This lineage was recovered as genetically differentiated from both O. tonkinensissensu stricto and Ovophis langbianus sp. nov., suggesting the presence of an additional independently evolving taxon within the O. tonkinensis complex. At present, the available material is insufficient for a comprehensive assessment of its taxonomic status. Additional sampling throughout northern Vietnam and southern China, combined with detailed morphological and molecular analyses, will be required to determine whether these populations represent a deeply divergent population of O. tonkinensis or an additional undescribed species. Nevertheless, our results clearly indicate that species diversity within the O. tonkinensis complex remains incompletely understood.

The description of Ovophis langbianus sp. nov. increases the number of currently recognized species in the genus Ovophis to ten. Vietnam now harbors four formally recognized species of Ovophis, including O. langbianus sp. nov., O. anitae, O. tonkinensis, and O. zhaoermii as well as populations provisionally referred to as O. cf. meridionalis. The latter taxon remains poorly understood and requires comprehensive taxonomic reassessment using both molecular and morphological evidence. Furthermore, several historical records of O. monticola and O. makazayazaya from Vietnam may represent misidentifications of O. anitae, O. cf. meridionalis, or additional undescribed taxa, and therefore require critical re-evaluation based on voucher specimens and molecular data. In particular, records of O. monticola from the Langbian Plateau, including those from Bidoup-Nui Ba National Park, and Chu Yang Sin National Park (e.g., Nguyen et al. 2009; Nguyen and Poyarkov 2020), including specimen NHMUK 1921.5.4.11 identified by Smith (1943), obviously represent Ovophis langbianus sp. nov., as members of the O. monticola complex possess paired subcaudals, a character state absent in all examined specimens from the Langbian Plateau. Given the complex geological history of the Indochinese mountain systems and the growing evidence for cryptic diversity within Ovophis, additional undescribed taxa are likely to occur in Vietnam and adjacent regions. Recent taxonomic studies have dramatically reshaped our understanding of species diversity within Ovophis, yet major gaps remain regarding the evolutionary history and biogeography of the genus. Future studies should prioritize range-wide sampling across the Annamite Mountains, southern China, and the eastern Himalayas, coupled with multilocus or genomic datasets. Such approaches will be essential for resolving species boundaries, clarifying phylogenetic relationships, and testing hypotheses regarding historical diversification processes across Asian montane systems.

The discovery of Ovophis langbianus sp. nov. further emphasizes the significance of the Langbian Plateau as a center of endemism and evolutionary diversification in mainland Indochina. Similar patterns of deep divergence between Langbian populations and their northern relatives have been documented in numerous amphibian and reptile groups, suggesting that long-term geographic isolation of the southern Annamite Highlands has played a key role in generating regional biodiversity. Continued integrative taxonomic investigations in this region will likely reveal additional cryptic diversity and contribute to a more complete understanding of the evolutionary history of Southeast Asian montane faunas.

 Acknowledgements

The fieldwork was completed within the framework of, and with partial financial support from, the research project “Conservation, restoration, and sustainable use of tropical forest ecosystems based on the study of their structural and functional organization” of the Joint Vietnam-Russia Tropical Science and Technology Research Center. Fieldwork in Chu Yang Sin National Park (Dak Lak Province), Bidoup-Nui Ba National Park (Lam Dong Province), and Hon Ba Nature Reserve (Khanh Hoa Province), including specimen collection in the field, was authorized by the Forestry Department and the People’s Committees of Dak Lak and Lam Dong provinces, Vietnam. Work in Chu Yang Sin NP was conducted under permits No. 1567/UBND-TH (of 06 April 2011) and No. 170/TCLN-BTTN (of 07 February 2013), work in Hon Ba NP was conducted under permits No. 522/SngV-TTDN&HTQT (of 13 June 2013) and No. 831/TCLN-BTTN (of 05 June 2013), whereas work in Bidoup-Nui Ba NP was conducted under permit No. 5832/UBND-LN (of 22 October 2012); No. 1169/UBND-NV4 (of 17 May 2022); and No. 54/VP-NV4 (of 21 January 2025). All permits were issued to VRTC. We are grateful to Valentina F. Orlova and Roman A. Nazarov (ZMMU) for providing access to specimens under their care. N.A.P. and A.M.B. thank Andrei N. Kuznetsov, Svetlana P. Kuznetsova, Hoi Dang Nguyen, and Leonid P. Korzoun for logistical support and assistance during fieldwork. We thank Huy Xuan Ngoc Nguyen (Vietnam) for sharing valuable information and photographs of Ovophis specimens. N.A.P. also thanks members of the MSU HerpLab, including Vladislav A. Gorin, Evgeniya N. Solovyeva, Alexey V. Trofimets, Nikita S. Kliukin, and Dmitriy V. Akhipov, for their continuous support and assistance. We are particularly grateful to Phuc Trong Nguyen (SIFASV, Vietnam) for his invaluable help in preparing the figures and distribution map. We also thank Yuhao Xu, Shuo Qi, and Arthur Tiutenko for their constructive comments on an earlier version of the manuscript.

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The authors have declared that no competing interests exist.

 Ethical statement

All procedures involving animal handling and specimen collection were approved by the Institutional Ethical Committee of the Joint Vietnam–Russia Tropical Science and Technology Research Center. Fieldwork and specimen collection were conducted under the relevant permits issued by the competent authorities in Vietnam.

 Artificial Intelligence (AI) use

The authors accept full responsibility for the content of the manuscript, including the disclosure of any use of AI.

No AI tools were used in the preparation of this manuscript.

 Funding

This work was supported by the Russian Science Foundation (Grant No. 22-14-00037-P) awarded to N.A. Poyarkov, which supported specimen collection and preservation, molecular and morphological analyses, and data processing. Additional support was provided by the Thailand Science Research and Innovation Fund and the University of Phayao, Unit of Excellence 2026 (Grant No. UoEICA002), Unit of Excellence 2027 on Aquatic Animals Biodiversity Assessment (Phase III) to C. Suwannapoom, and by the Rufford Foundation (Grant No. 51772-B; data analysis) to T.V. Nguyen.

 Author contributions

All authors have contributed equally.

 Author ORCIDs

N.A. Poyarkov https://orcid.org/0000-0002-7576-2283

S.S. Idiiatullina https://orcid.org/0000-0003-1647-7754

A.M. Bragin https://orcid.org/0000-0002-3621-9763

S.X. Le https://orcid.org/0009-0000-6299-7844

P. Pawangkhanant https://orcid.org/0000-0002-0947-5729

C. Suwannapoom https://orcid.org/0000-0002-3342-1464

P. David https://orcid.org/0000-0001-7562-684X

G. Vogel https://orcid.org/0000-0002-4542-518X

T.V. Nguyen https://orcid.org/0000-0001-5413-968X

 Data availability

All of the data that support the findings of this study are available in the main text or Supplementary Information.

 Supplementary materials 10.3897/herpetozoa.39.e206094.suppl1 B345988D-CCA0-548E-A64C-008BB2CE98A7

Additional figures and tables

pdf

fig. S1. Paratype of Ovophis langbianus sp. nov. in preservative (ZMMU Re-13839, adult female). fig. S2. Paratype of Ovophis langbianus sp. nov. in preservative (ZMMU Re-14068, adult male). fig. S3. Paratype of Ovophis langbianus sp. nov. in preservative (ZMMU Re-18511, adult male). table SS1. Sample ID, GenBank accession numbers, localities, & references of the sequences of the genus Ovophis & outgroup taxa used in this study. table SS2. Measurements (in mm) and meristic characters of the examined specimens of Ovophis langbianus sp. nov. and O. tonkinensis. table S3. Uncorrected p-distances (percentage) based on cyt b mitochondrial sequences among species of the genus Ovophis included in the phylogenetic analyses. table S4. List of localities of the Ovophis tonkinensis complex appearing on Fig. 1.

 https://binary.pensoft.net/file/1754167 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0/). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Nikolay A. Poyarkov, Sabira S. Idiiatullina, Darya A. Ustinova, Andrey M. Bragin, Son Xuan Le, Parinya Pawangkhanant, Hieu Minh Pham, Chatmongkon Suwannapoom, Patrick David, Gernot Vogel, Tan Van Nguyen