Sang Ngoc Nguyen

A new wolf snake, genus Dinodon, from the Langbian Plateau of Vietnam is described based on morphological data and nucleotide sequences from mitochondrial genes COI and Cytb. Dinodon orlovi sp. nov. is diagnosed by the following morphological characters: medium-sized wolf snake (largest snout–vent length 668 mm in adult female); dorsal scale rows 17-17-15, keeled at midbody and posterior part; ventrals 209–212 in males and 213–217 in females; subcaudals 76 in males and 70 in female; supralabials 8, third to fifth entering orbit; maxillary teeth 13, formula 7-3-3; hemipenis unforked, reaching 11th–13th subcaudal, with spinulate calyces at distal part and enlarged curved spines at middle part; cloacal plate single; head bicolor, viz. black anteriorly and white posteriorly; light cross-bands 17–23 on body and 11–13 on tail. The new species differs from its congeners by an uncorrected p-distance in COI and Cytb sequences of at least 4.4% and 3.3%, respectively.

We describe a new species of wolf snake, genus Dinodon, from Lam Dong Province, southern Vietnam, based on morphological characters and molecular evidence from mitochondrial COI, Cytb, and 16S. Dinodon nuiongensis sp. nov. is diagnosed by the following combination of morphological features: a medium-sized species, reaching up to 630 mm in total length; 8 or 9 supralabials, with the third to fifth contacting the eye; 10 infralabials; a single loreal contacting the eye; 11 maxillary teeth; dorsal scale rows 17-17-15, with 7–11 keeled rows at neck and 9–11 at midbody; 210 or 211 ventrals; cloacal plate single; 74–82 paired subcaudals; hemipenis unforked, extending to the 8th or 9th subcaudal, with distal spinulate calyces, enlarged curved spines at middle part, and single sulcus spermaticus; and 19–23 and 11–14 cross-bands on the body and tail, respectively. The new species differs from its congeners by uncorrected p-distances of at least 8.9% for COI, 8.7% for Cytb, and 1.0% for 16S.

Comparative phylogeography provides a powerful framework to identify the historical processes shaping biodiversity hotspots by testing whether co-distributed species exhibit shared patterns of diversification. Southeast Asia harbors exceptional biodiversity, yet the extent to which common paleogeographic and climatic drivers have structured diversification across taxa remains poorly understood. Here, we investigated the evolutionary history of five widespread Microhyla species complexes distributed across the Indochinese Peninsula and adjacent regions using dense mitochondrial sampling (1,388 individuals) combined with genome-scale ddRAD sequencing (280 individuals). Across all complexes, both approaches recovered multiple lineages and remarkably congruent phylogeographic breaks and contact/intergradation zones associated with major Indochinese regions, including Myanmar, the Tenasserim-Malay Peninsula, southern Vietnam, and northern Vietnam-southern China, supporting the hypothesis that Indochina functions as a mosaic of stable biogeographic units. However, lineage divergence varied substantially among complexes, suggesting that common biogeographic drivers interacted with species-specific demographic histories. Phylogenomic analyses and cyto-nuclear discordance further revealed historical introgression in every complex, indicating that diversification involved both long-term allopatric isolation and reticulate evolution. These findings portray the Indochinese biodiversity hotspot as a dynamic evolutionary system where cycles of fragmentation and reconnection have repeatedly reshaped lineage boundaries. Moreover, the complex phylogeographic structure recovered exemplifies the urgent need for taxonomic revisions, for which genome-scale data provide an essential framework to validate mitochondrial hypotheses and assess admixture patterns for species delimitation. Finally, regions such as the southern Annamites and Tenasserim Hills emerged as recurrent hotspots of genetic diversity across independent lineages, highlighting their importance for conserving not only species/lineage richness but also the evolutionary processes and adaptive potential that sustain biodiversity.

We describe a new keelback snake of the genus Hebius from the Ngoc Linh Mountain Range, Central Highlands, Vietnam, based on morphological characters and molecular evidence (Cytb). Hebius ngoclinhensis sp. nov. is diagnosed by the following combination of morphological features: dorsal scale rows 19-19-17; first dorsal scale row smooth; ventrals 143–148; subcaudals 95–97, paired; two preoculars; two or three postoculars; one loreal; eight or nine supralabials; ten infralabials; cloacal plate divided; maxillary teeth 24–26, gradually enlarged, with two distinctly enlarged teeth posteriorly; 17 keeled dorsal scale rows at midbody; dorsal surface of body and tail dark brown with numerous irregular dark yellow spots; a distinct reddish-brown dorsolateral stripe on the 4th–7th dorsal scale rows on each side; ventral surface of body and tail reddish-orange to orange; and lateral margins of ventrals and subcaudals dark brown. In addition, the new species differs from its congeners by an uncorrected p-distance in Cytb sequences of at least 9.3%.

Two new skinks of the genus Scincella Mittleman, 1950, from Khanh Hoa and Binh Thuan provinces, southern Vietnam, are described based on differences in morphology and nucleotide sequences. Scincella honbaensis sp. nov. is diagnosed by the following morphological characters: 28 smooth midbody scale rows; dorsal scales enlarged, six rows on back; 64 paravertebrals; 74 ventral scale rows; prefrontals in broad contact with one another; one anterior and two posterior enlarged temporals; three pairs of nuchals; 21 smooth lamellae beneath toe IV; dorsum with two longitudinal rows of black dots. Scincella auranticaudata sp. nov. is diagnosed by the following morphological characters: 34–36 smooth midbody scale rows; dorsal scales not enlarged, ½+8+½ rows on back; 67–74 paravertebrals; 65–69 ventral scale rows; prefrontals separated from or just in contact with one another; two anterior and two posterior enlarged temporals; one pairs of nuchals; 17–20 smooth lamellae beneath toe IV; hemipenis smooth, forked near the base with two long symmetrical lobes; dorsum with a vertebral line formed by large black spots. Scincella honbaensis and Scincella auranticaudata differ from their congeners by an uncorrected p-distance in COI sequences of at least 16.7% and 9.4%, respectively.

We describe a new frog of the genus Limnonectes from the Langbian Plateau in southern Vietnam based on morphological and molecular analyses. Limnonectes splendissimus sp. nov. shares morphological characteristics similar to L. poilani from central Vietnam yet is distinguishable from its congeners based on the following combination of diagnostic characters: large body-size (SVL 104.1–107.0 mm in three adult males, 87.2–97.7 mm in two adult females); head length longer than wide (HW/HL = 0.91±0.01 in adult males, 0.87±0.08 in adult females); adult males having an enlarged head height and a nuptial pad on finger I; eye diameter about three-fifths of tympanum-eye distance in adult males (ED/TED = 0.62±0.13) and longer than tympanum-eye distance in adult females (ED/TED = 1.40±0.02); distinct tympanum; presence of vomerine teeth; a tendency for a more prominent odontoid height (OH 8.0 ± 0.6 mm in adult males, 4.5±0.9 mm in adult females); throat surface in juveniles very distinct with black and white pattern that covers both the throat and anterior half of venter, and latter half of venter yellow. Phylogenetic analyses place the new species as the sister species of L. poilani. The new species differs from its congeners by an uncorrected p-distances in 16S sequences ranging from 8.2% (vs. L. poilani) to 14.6% (vs. L. dabanus).

Homalopsids (Old World Mud Snakes) include 59 semiaquatic species in Asia and Australasia that display an array of morphological adaptations, behaviors, and microhabitat preferences. These attributes make homalopsids an ideal model system for broader questions in evolutionary biology, but the diversity of this understudied group of snakes is still being described. Recognized species diversity in rice paddy snakes (Hypsiscopus) has recently doubled after nearly 200 years of taxonomic stability. However, the evolutionary distinctiveness of some populations remains in question. In this study, we compare mainland Southeast Asian populations of Hypsiscopus east and west of the Red River Basin in Vietnam, a known biogeographic barrier in Asia, using an iterative approach with molecular phylogenetic reconstruction, machine-learning morphological quantitative statistics, and ecological niche modeling. Our analyses show that populations west of the Red River Basin represent an independent evolutionary lineage that is distinct in genetics, morphospace, and habitat suitability, and so warrants species recognition. The holotype of H. wettsteini, a species originally described in error from Costa Rica, grouped morphometrically with the population at the Red River Basin and eastward, and those west of the Red River Basin are referred to the recently described H. murphyi. The two species may have diversified due to a variety of geological and environmental factors, and their recognition exemplifies the importance of multifaceted approaches in taxonomy for downstream biogeographic studies on speciation scenarios.

Homalopsid snakes of the genus Myrrophis include only two species distributed in southern China and northern Vietnam. Here, we describe a third species from southern Vietnam based on morphological data and nucleotide sequences from the mitochondrial gene cyt b. Myrrophis dakkrongensis sp. nov. is diagnosed by the following morphological characters: Medium-sized mud snake (largest total length 452 mm); internasal single and distinctly separated from loreals; dorsal scales smooth, in 23 rows at midbody, reduced to 19 or 20 rows before vent; ventrals 133–138; subcaudals 34–42, paired; cloacal plate divided; supralabials 8, fourth entering orbit; second pair of chin-shields small and oblique; maxillary teeth 17 or 18; gland-like tubercles present in the cloacal region; hemipenis short, forked and spinose, reaching 7th subcaudal; dorsum dark brown to black; and a white or yellow to orange lateroventral stripe present. The new species differs from its congeners by an uncorrected p distance in cyt b sequences of at least 10.5%.

Rat snakes (genus Ptyas) include 13 large Asian species with sizes reaching 3.8 m. For more than 100 years, no new species have been discovered in this genus. Here, we describe a new Ptyas from central Vietnam based on morphological data and nucleotide sequences from the MT-CYB gene. Ptyas bachmaensis sp. nov. is diagnosed by the following morphological characters: large-sized snake (largest total length 2 401 mm in adult male); body scale rows in even numbers, 16-16-14 rows; two medial vertebral scale rows distinct; two and two or four medial scale rows keeled on middle and posterior parts of body, respectively; ventrals 194-199; subcaudals 132-138; supralabials 8, fourth and fifth entering orbit; maxillary teeth 28 or 29; hemipenis spinose and unforked, reaching 12 th subcaudal; cloacal plate divided; lateral side of tail black, without a bright stripe. The new species forms an independent clade on the phylogenetic tree and differs from its congeners by an uncorrected p-distance in MT-CYB sequences of at least 5.7%.

A new species of the genus Vietnamophryne is described from Vietnam on the basis of two specimens collected from Tuyen Quang Province, Northeastern Vietnam. The new species is morphologically most similar to Vietnamophryne occidentalis from Thailand, however, it differs from the latter by having large black blotches in the lower jaw region, and a yellow-orange chest and belly. The genetic distance between the new species and other Vietnamophryne taxa is > 2.13% (16S mtDNA gene fragment). Vietnamophryne aurantifusca sp. nov. can be distinguished from all other species of Vietnamophryne by a combination of the following morphological characteristics: Size medium (SVL 17.6–18.2 mm in males); head wider than long; tympanum medium; finger I longer than half of finger II; dorsal skin relatively smooth with some round nodules, concentrated in the middle of the back, arranged along the length of the back, with a prominent ridge along the spine; Dorsum orangish-brown entirely and paler on margin of back with a small brownish ridge along the spine; sides brownish with creamy patches and orange spots; ventral surface orange, with grey marbling, most intense on the throat, ventral side of arms and thighs, and ventral surfaces of limbs dark grey with some orange spots.