Despite recent progress in our understanding of diversity within the genus Trimeresurus Lacépède, 1804, the subgenus Popeia Malhotra & Thorpe, 2004, distributed across most parts of East and Southeast Asia, remains taxonomically challenging. We applied an integrative taxonomic approach including analyses of morphological data and four mitochondrial genes (12S and 16S rRNA, cytochrome b, and NADH dehydrogenase subunit 4), along with examination of available type material, to address longstanding taxonomic questions in one clade within Popeia, the T. popeiorum group, and reveal a high level of hidden diversity of these snakes in the Indo-Burma Biodiversity Hotspot. We confirm that T. popeiorum Smith, 1937 sensu stricto is restricted to Northeast India, eastern Nepal, southern Bhutan, southeastern Bangladesh, western Yunnan Province (China), and northern and southwestern Myanmar. We further confirm that the recently described species T. yingjiangensis Chen et al., 2019 is a junior synonym of T. popeiorum. In addition, we discovered that the combination Trimesurus [sic] elegans Gray, 1853 is a valid senior synonym of T. popeiorum and threatens the stability of the latter taxon. Therefore, in order to protect the nomen popeiorum and in accordance with Article 23.9 of the International Code of Zoological Nomenclature, we regard the taxon Trimesurus elegans as a nomen oblitum and render Trimeresurus popeiorum a nomen protectum. Examination of a larger series of specimens allows us to describe two new cryptic species of Trimeresurus from the Indo-Burma Region. This study brings the total number of species in the subgenus Popeia to six and also suggests that the subspecific taxonomy of the T. sabahi complex requires further investigation. We urge adequate actions regarding the conservation of the newly discovered species and recommend further studies on their toxicology.

Berdmore’s narrow-mouthed frog, Microhyla berdmorei (Blyth, 1856), is the largest member of the genus Microhyla and is distributed all over Southeast Asia, from Northeast India and southern China to Sumatra and Borneo in Indonesia. Here we demonstrate that M. berdmorei represents a complex of four species that are morphologically, acoustically, and genetically distinct from each other, and we implement taxonomic revisions. Phylogenetic analyses of three mitochondrial DNA (hereafter mtDNA, including COI, 12S, and 16S rRNA; 3119 bp) and one nuclear (BDNF; 716 bp) gene sequences are corroborated by phylogenomic analyses of 2700 ddRAD-seq loci (387,270 bp). All support that the M. berdmorei complex, which originates from the early Miocene (ca. 19.7 mya), consists of two clades that we date to the late Miocene (ca. 7.5 mya). The first clade, which regroups populations of large-sized individuals, is distributed in Indo-Burma and includes a lineage from Northeast India, Bangladesh, and Myanmar (M. berdmorei sensu stricto) and a lineage from West Malaysia, Thailand, Laos, Cambodia, and Vietnam (for which we propose to resurrect the species M. malcolmi Cochran, 1927). The second clade, which regroups populations of small-sized individuals, occurs in Sundaland and also includes two lineages for which we provide taxonomic descriptions on species rank. The first new species is widely distributed from Peninsular Malaysia to the islands of Borneo and Sumatra (described herein as M. sundaicasp. nov.), while the second one is restricted to the Malay Peninsula and occurs in extreme southern Thailand and adjacent Malaysia (M. peninsularissp. nov.). We further provide evidence for the synonymy of Callula natatrix Cope, 1867 with M. berdmorei sensu stricto, and M. fowleri Taylor, 1934 with M. malcolmi. Our study illustrates the high diversity of Southeast Asian amphibians, especially in the genus Microhyla, which presently totals 54 species.

Despite increased attention by molecular taxonomists, the herpetofauna of Southeast Asia still hides many undescribed species among far-ranging taxa. In this study, we re-examine the mitochondrial diversity of painted frogs of the microhylid genus Kaloula, based on ~2,455 bp of published and new 12S and 16S rRNA sequences, and describe two new species from the tropical forests of southern Vietnam and central Laos based on integrative evidence. These species, which belong to the K. baleata complex, feature species-level mitochondrial divergence (> 4.4% at 16S rRNA) and are both morphologically well-differentiated from each other and from the recently described K. indochinensis, to which they were previously confounded. Comparative examinations also indicate distinct male advertisement calls and unique coloration features. Based on genetic barcoding, we preliminarily revise the species distribution ranges in the K. baleata complex, which support a general pattern of biogeographic partitioning that has been widely retrieved among the Indochinese amphibians studied so far. Molecular diversity within K. baleata further suggests genetic structure across Sundaland, namely three shallow mitochondrial haplogroups worthy of fine-scale phylogeographic and taxonomic investigations. Furthermore, our study highlights the propensity of amphibian species “hidden in plain sight,” even among recently studied taxa, thus calling for caution when specifying type specimens—the type series of K. indochinensis, described in 2013, includes specimens of the one of the new species. Our study emphasizes the continued need for thorough herpetological surveys even in supposedly well-known parts of Indochina and sets the ground for future research in Kaloula painted frogs, notably to test evolutionary and taxonomic hypotheses with genomic loci.

We describe a new species of rhacophorid frogs from Nghe An Province in northern Vietnam based on morphological and molecular evidences. Morphologically, Kurixalus gracilloides sp. nov. is distinguished from its congeners by a combination of the following diagnostic characters: body size small (snout–vent length 27.9–31.2 mm in males); head width subequal to head length; snout rounded with no dermal projection; canthus rostralis distinct, curved; vomerine teeth present; single internal vocal sac; iris golden-brown; small nuptial pad in finger I; dorsal surfaces golden-brown with a saddle-shaped dark marking; large dark spots on ventral surfaces absent; dermal fringes along outer edge of limbs; conical dermal appendage at the heel; skin on dorsum rough; skin on throat and chest granular; finger webbing rudimentary and toe webbing moderately developed, webbing formula I 2–2½ II 1½–3 III 1¾–3½ IV 3–1½ V. The new species is separated from all other congeners by uncorrected genetic distances ranging from 5.4% to 12.7% based on mitochondrial 16S rRNA gene. Phylogenetic analyses of mtDNA suggest that the new species is nested within a clade of Taiwanese and Yunnan Kurixalus with strong support values. The new species is currently known only from secondary bamboo forest in Pu Mat National Park, northern Vietnam, at elevations of 150 m asl. We suggest the new species should be considered as Near Threatened (NT) following the IUCN’s Red List categories. http://www.zoobank.org/urn:lsid:zoobank.org:pub:C1BF843F-2F31-4CED-B1F9-13A9035C77C9

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

In the frame of our investigations on the systematics of the complex of species of Trimeresurus albolabris, we came across specimens from Myanmar variously referred to as Trimeresurus albolabris Gray, 1842 or T. septentrionalis Kramer, 1977 in the literature. We describe a new species of green pitviper of the genus Trimeresurus Lacépède, 1804 from central and southern Myanmar based on molecular analyses drawn from previously published phylogenies and new morphological data. This new species, Trimeresurus uetzi sp. nov., is broadly similar to both Trimeresurus albolabris and T. septentrionalis, but it differs from these latter species by a series of morphological characters such as presence of white pre- and postocular streaks in male, iris copper in male or green gold in female, more ventral plates, and a much shorter hemipenis. We compare this new species with Trimeresurus albolabris as currently defined and other species of this complex. We also emphasize the need for additional integrated studies on Trimeresurus albolabris sensu lato populations distributed in southern Indochina and Sundaland.