Despite continuous progress made on the taxonomy of the genus Tropidophorus,the Lao Water Skink,T.laotus,is only known from brief descriptions of its syntypes in historical literature.Here we designate a lectotype and paralectotype of the species,redescribe the species based on the type series and newly collected topotypes,provide the first colored photographs of taxonomically-verified individuals,and estimate its phylogenetic position using mitochondrial DNA data for the first time.Using these comparable data,we confirm that the previously identified"T.berdmorei"population from southern Yunnan Province,China,represents a distinct new species that is closely related and morphologically similar to T.laotus,but differs from true T.laotus by having considerable genetic divergence(4.7%-4.8%for 12S,3.2%-4.2%for 16S)and distinct morphological characters(e.g.,undivided frontonasal scales and a distinct color pattern of the throat).The southern Yunnan population is therefore described as a new species.With the above newly acquired data,we update the checklist and the provincial-level distribution of the genus Tropidophorus in China and compile an updated key to all recognized species of the genus from China and Indochina.

Dixonius is a monophyletic gekkonid lizard genus endemic to Southeast Asia, with 50% of the described species in the genus occurring within Thailand. In Thailand, several new species were recently described solely based on morphology. However, the phylogenetic position and systematics of these species remain unknown due to a lack of genetic data. To verify the taxonomic status and phylogenetic placement of Dixonius species in Thailand, we obtained and analyzed sequences of the mitochondrial NADH dehydrogenase subunit 2 (ND2) gene from seven nominal Dixonius species (D. dulayaphitakorum, D. hangseesom, D. kaweesaki, D. mekongensis, D. melanostictus, D. pawangkhananti and D. siamensis) collected from their type localities in Thailand. Our results provide the first genetic data of several Dixonius species in Thailand, notably the type species, D. siamensis. The validity of seven nominal Dixonius species in Thailand was confirmed with well-supported lineages. Interestingly, this study reports a new national record of D. somchanhae from Bueng Kan, northeastern Thailand, approximately 100 km from its type locality. This result brings the total number of nominal Dixonius species occurring in Thailand to ten. Furthermore, we found that D. melanostictus and D. cf. siamensis from other populations outside of their type localities should be tentatively considered as undescribed species. Our findings suggest that the diversity of Dixonius in Thailand has been underestimated. Additional specimens and genetic data across their ranges, especially D. chotjuckdikuli, are needed for both molecular and morphological analyses to further clarify the phylogenetic relationships and true diversity of the genus Dixonius in Thailand.

In recent years, hybridization has come into focus as a potent force with a myriad of evolutionary outcomes. Natural hybridization has been documented across the hylid treefrog genus Dryophytes, but few studies have demonstrated the origins of putative natural hybrids. Here, we use molecular and acoustical data to test the parentage of 2 putative D. chrysoscelis x D. femoralis hybrids found in the wild in Virginia and North Carolina. Using 1 mitochondrial and 4 nuclear loci, we demonstrate that these 2 individuals are genetically intermediate between D. chrysoscelis (Cope's Gray Treefrog) and D. femoralis (Pine Woods Treefrog), with differing maternal species. The mating calls of hybrids are consistent with those of previous studies and feature a breakdown in structure that may result from an intermediate phenotype between the unpulsed and pulsed notes of the respective parent species. While hybridization between the 2 species is apparently rare, our results combined with previous laboratory studies demonstrate the potential for introgressive hybridization, necessitating further work to identify the extent of hybridization in the system.

A new species of the Cnemaspis siamensis group is described from Wang Khrachae District, Kanchanaburi Province, western Thailand based on morphological and molecular data. The new species, Cnemaspis enneaporus Rujirawan, Aksornneam & Aowphol, sp. nov., is distinguished from other species in the C. siamensis group by having the combination of SVL 42.2 mm in adult male (n = 1), 43.7 mm in adult female (n = 1); eight supralabials; seven or eight infralabials; ventral scales smooth; nine continuous precloacal pores in male; 17 or 18 paravertebral tubercles linearly arranged; tubercles on lower flanks present; lateral caudal furrows present; no caudal tubercles in the lateral furrows; ventrolateral caudal tubercles present on original portion of tail; caudal tubercles not encircling tail; subcaudals smooth; no enlarged median subcaudal row; two postcloacal tubercles on each side of tail; no shield-like subtibial scales; subtibial scales smooth; no enlarged submetatarsal scales; 26-28 subdigital lamellae on the fourth toe; sexually dimorphic for dorsal and ventral colour pattern; prescapular marking absent; gular marking absent; and yellow colouration in life on all ventral surfaces of head, body and tail in adult male. Phylogenetically, the new species is recovered as the sister taxon to C. huaseesom, but the two species are separated by 8.3-9.4% uncorrected pairwise genetic divergences in the mitochondrial NADH dehydrogenase subunit 2 gene and flanking tRNAs.

We describe a new species of dicroglossid frog in the genus Limnonectes from the Phu Phan Mountain Range, Sakon Nakhon Province, northeastern Thailand. Molecular phylogenetic analyses, based on the mitochondrial 16S ribosomal RNA gene, revealed that Limnonectes sirindhornae Rujirawan, Yodthong & Aowphol, sp. nov. is closely related to L. lauhachindai but has mean uncorrected pairwise genetic divergences of 4.25%. The new species can be distinguished from its congeners by having the combination of SVL 36.7–44.7 mm (n = 8) in adult males, 40.2–45.6 mm (n = 8) in adult females; adult males with hypertrophied heads; adult males with interorbital caruncle weakly developed, low-profiled, U-shaped, without free posterior margin; two enlarged odontoid processes on anterior margin of lower jaw, larger in males than in females; vocal sac opening in males absent; and yellowish coloration in life on ventral surfaces absent.

The Ulu Temburong region in Bruneian Borneo is an exceptionally diverse, old-growth tropical rainforest that harbours unique species, including cryptic amphibians. In May 2017, we collected three caecilian specimens (Amphibia, Gymnophiona, Ichthyophis) from Ulu Temburong National Park, conducting morphological, molecular and cutaneous microbiome analyses. Comparisons of morphology, including CT scans, and mitochondrial DNA have determined the Temburong specimens to be Ichthyophis asplenius, previously not known from Brunei but documented elsewhere on Borneo. The Temburong specimens had continuous lateral body stripes, lacked splenial teeth and had body folds and grooves that did not cross the back on the anterior portion of the body. The mitochondrial DNA matched published sequences of I. asplenius from Sarawak, Malaysia. Our study pioneers the exploration of caecilian cutaneous microbiomes in the wild, marking the inaugural report from the Asian subcontinent. Microbial communities exhibited specimen-specific differences while maintaining uniformity across body locations. Proteobacteria dominated, aligning with previous studies, whereas Firmicutes and Acidobacteriota displayed intriguing variations between caecilian skin and the environment. This work constitutes the second caecilian species documented in Brunei and provides the initial wild caecilian microbiome description from Asia, contributing valuable insights into the biodiversity and microbial ecology of this important region.

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.

A new species of long-snouted arboreal snake of the genus Ahaetulla Link, 1807, is described from the Indian states of Bihar and Meghalaya. Molecular phylogenetic analysis using three mitochondrial genes recovered the new species as a member of the A. fusca clade and as a sister species to A. laudankia. The new species differs from its congeners in bearing an elongate rostral appendage, green or ochre dorsum, orange-brown belly, and moderately keeled vertebral dorsal scale row. This description of a new reptile species highlights the need for systematic documentation of biodiversity in the region.

The gekkonid lizard genus Hemiphyllodactylus contains small, secretive species that are often overlooked in their habitats. Recent molecular and morphological analyses have resulted in the descriptions of numerous new species of Hemiphyllodactylus in mainland Southeast Asia and southern China, many of which were historically hidden within the geographically widespread taxon H. yunnanensis (Boulenger, 1903). Little is known on species diversity and distributions of Hemiphyllodactylus in Cambodia, and all previous reports from the country have been limited to provisional identifications owing to collections containing only a single female or juvenile specimen. We report on new collections of Hemiphyllodactylus specimens from opposite ends of the Cardamom Mountain range in southwestern Cambodia. Morphological and molecular data support the hypothesis that these collections contain three distinct species, two of which are described as new species and one of which is assigned to the geographically widespread H. typus Bleeker, 1860 as a new country record for Cambodia. Hemiphyllodactylus bokor sp. nov. from Preah Monivong Bokor National Park in Kampot Province and Hemiphyllodactylus samkos sp. nov. from Phnom Samkos Wildlife Sanctuary in Pursat Province are related to species from adjacent areas in southern Vietnam, southern Laos, and southeastern Thailand, as well as a clade from India, but are readily differentiated in mitochondrial DNA and in having unique combinations of mensural and meristic morphological characters. Additional species diversity of Hemiphyllodactylus likely exists in Cambodia.

A new karst-dwelling bent-toed gecko of the Cyrtodactylus intermedius group is described from Khlong Hat District, Sa Kaeo Province, eastern Thailand, based on an integrative taxonomic analysis of genetic data and morphological characteristics. Phylogenetic analyses using the mitochondrial NADH dehydrogenase subunit 2 (ND2) gene revealed that topotypes of C. intermedius were sister to a clade containing C. kulenensis from Cambodia, an unnamed lineage from Sakaerat Biosphere Reserve in Nakhon Ratchasima Province, Thailand, and the Khlong Hat lineage described here as Cyrtodactylus khlonghatensissp. nov. Multivariate analyses of morphometric and meristic characters showed that C. khlonghatensissp. nov. is morphologically distinct from all other species in the group by having the combination of SVL 76.5–82.8 mm in adult males and 88.5 mm in an adult female; eight supralabial and nine infralabial scales; 30–32 paravertebral tubercles; 20 or 21 longitudinal rows of dorsal tubercles; 43 or 44 ventral scales; seven or eight expanded subdigital lamellae on the 4th toe; 12 unmodified subdigital lamellae on the 4th toe; 19 or 20 total subdigital lamellae on the 4th toe; 31 or 32 total number of enlarged femoral scales; enlarged femoral and precloacal scales continuous; 6–8 pore-bearing precloacal scales in males; three or four rows of enlarged post-precloacal scales; 1–3 postcloacal tubercles; proximal femoral scales less than one-half the size of distal femoral scales; absence of interdigital pocketing between digits of forefeet and hindfeet; and posterior border of the nuchal loop rounded. Uncorrected pairwise genetic divergences (p-distances) between the new species and other species of the intermedius group ranged from 4.73–22.55%. The discovery of this new species exclusively in isolated karst formations from the Thai-Cambodia border suggests that there may be further undiscovered Cyrtodactylus in unexplored karst landscapes along the border of eastern Thailand and western Cambodia.

Divergence dating analyses in systematics provide a framework to develop and test biogeographic hypotheses regarding speciation. However, as molecular datasets grow from multilocus to genomic, sample sizes decrease due to computational burdens, and the testing of fine-scale biogeographic hypotheses becomes difficult. In this study, we use coalescent demographic models to investigate the diversification of poorly known rice paddy snakes from Southeast Asia (Homalopsidae: Hypsiscopus ), which have conflicting dates of origin based on previous studies. We use coalescent modeling to test the hypothesis that Hypsiscopus diversified 2.5 mya during the Khorat Plateau uplift in Thailand. Additionally, we use ecological niche analyses to identify potential differences in the niche space of the two most widely distributed species in the past and present. Our results suggest Hypsiscopus diversified ~ 2.4 mya, supporting that the Khorat Plateau may have initiated the diversification of rice paddy snakes. We also find significant niche differentiation and shifts between species of Hypsiscopus , indicating that environmental differences may have sustained differentiation of this genus after the Khorat Plateau uplift. Our study expands on the diversification history of snakes in Southeast Asia, and highlights how results from smaller multilocus datasets can be useful in developing and testing biogeographic hypotheses alongside genomic datasets.

As the discovery of cryptic species has increased in frequency, there has been an interest in whether geometric morphometric data can detect fine-scale patterns of variation that can be used to morphologically diagnose such species. We used a combination of geometric morphometric data and an ensemble of five supervised machine learning methods (MLMs) to investigate whether plastron shape can differentiate two putative cryptic turtle species, Actinemys marmorata and Actinemys pallida. Actinemys has been the focus of considerable research due to its biogeographic distribution and conservation status. Despite this work, reliable morphological diagnoses for its two species are still lacking. We validated our approach on two datasets, one consisting of eight morphologically disparate emydid species, the other consisting of two subspecies of Trachemys (T. scripta scripta, T. scripta elegans). The validation tests returned near-perfect classification rates, demonstrating that plastron shape is an effective means for distinguishing taxonomic groups of emydids via MLMs. In contrast, the same methods did not return high classification rates for a set of alternative phylogeographic and morphological binning schemes in Actinemys. All classification hypotheses performed poorly relative to the validation datasets and no single hypothesis was unequivocally supported for Actinemys. Two hypotheses had machine learning performance that was marginally better than our remaining hypotheses. In both cases, those hypotheses favored a two-species split between A. marmorata and A. pallida specimens, lending tentative morphological support to the hypothesis of two Actinemys species. However, the machine learning results also underscore that Actinemys as a whole has lower levels of plastral variation than other turtles within Emydidae, but the reason for this morphological conservatism is unclear.

The gekkonid lizard Cyrtodactylus intermedius was formerly considered to be a single widespread species in hilly areas across eastern Thailand through southern Vietnam but has recently been partitioned into a complex of 12 nominal species across its range. A population belonging to the C. intermedius group was recently found in an isolated limestone karst block in Kampot Province in southwestern Cambodia, part of which lies within the recently designated Phnom Preah Kuhear Loung Natural Heritage Site. Comparisons of morphometric, meristic, qualitative morphological and color pattern data, as well as a molecular analysis using the mitochondrial ND2 gene, revealed that this population differs from all other named members of the C. intermedius group, and so is described here as a new species. The karst-dwelling C. regicavernicolus sp. nov. was recovered as the sister species to C. laangensis, the most geographically proximate member of the complex and one that is also restricted to a small limestone karst habitat.

DNA barcoding has greatly facilitated studies of taxonomy, biodiversity, biological conservation, and ecology. Here, we establish a reliable DNA barcoding library for Chinese snakes, unveiling hidden diversity with implications for taxonomy, and provide a standardized tool for conservation management. Our comprehensive study includes 1638 cytochrome c oxidase subunit I (COI) sequences from Chinese snakes that correspond to 17 families, 65 genera, 228 named species (80.6% of named species) and 36 candidate species. A barcode gap analysis reveals gaps, where all nearest neighbour distances exceed maximum intraspecific distances, in 217 named species and all candidate species. Three species-delimitation methods (ABGD, sGMYC, and sPTP) recover 320 operational taxonomic units (OTUs), of which 192 OTUs correspond to named and candidate species. Twenty-eight other named species share OTUs, such as Azemiops feae and A. kharini, Gloydius halys, G. shedaoensis, and G. intermedius, and Bungarus multicinctus and B. candidus, representing inconsistencies most probably caused by imperfect taxonomy, recent and rapid speciation, weak taxonomic signal, introgressive hybridization, and/or inadequate phylogenetic signal. In contrast, 43 species and candidate species assign to two or more OTUs due to having large intraspecific distances. If most OTUs detected in this study reflect valid species, including the 36 candidate species, then 30% more species would exist than are currently recognized. Several OTU divergences associate with known biogeographic barriers, such as the Taiwan Strait. In addition to facilitating future studies, this reliable and relatively comprehensive reference database will play an important role in the future monitoring, conservation, and management of Chinese snakes.

The Lao torrent frog Amolops cremnobatus Inger & Kottelat, 1998 was recently hypothesized, based on mitochondrial DNA, to consist of more than a single species across its range in Laos and flanking regions of Vietnam and Thailand. We tested this hypothe-sis using mitochondrial DNA, nuclear DNA, and quantitative and qualitative morphological data from adults and larvae. We found corroborating lines of evidence for five distinct evolutionary lineages that we hypothesize to be species. Amolops cremnobatus sensu stricto is restricted to the southeastern portion of its previous range, and remaining populations are described as four new species. Some of the new species are easier to diagnose with morphology as larvae than as adults. Further sampling in northern Thailand may reveal an additional species of this torrent frog complex.

DEAR EDITOR,Based upon morphological and molecular evidence, the authors revised the genus Rohanixalus Biju, Garg,Gokulakrishnan, Chandrakasan, Thammachoti, Ren, Gopika,Bisht, Hamidy and Shouche, 2020（Anura: Rhacophoridae） in China through describing one new species, adding one species to the fauna（R. shyamrupus） and supplementing data on one species（Rohanixalus hansenae; Supplementary Materials）. Rohanixalus wuguanfui sp. nov. can be distinguished by the following combination of characters:

Limnonectes liui (Yang, 1983) is a poorly known frog from Yunnan Province, China, with a confusing taxonomic history. We use mitochondrial (mt) DNA sequence data from newly collected specimens to reconstruct the phylogenetic position of the species. Limnonectes liui was found to be deeply nested within the geographically widespread dicroglossid frog L. limborgi (Sclater, 1892), verifying its placement within the genus Limnonectes but casting doubt on its distinction as a species. Morphological comparisons of the holotype and newly collected specimens of L. liui to specimens of L. limborgi from across its range also corroborated the hypothesis that these two species are conspecific, and we recommend treating L. liui as a junior synonym of L. limborgi. Our study underscores the importance of making comparisons with species found beyond a countrys border when describing new species.