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Systematic assessments of species extinction risk at regular intervals are necessary for informing conservation action 1,2 . Ongoing developments in taxonomy, threatening processes and research further underscore the need for reassessment 3,4 . Here we report the findings of the second Global Amphibian Assessment, evaluating 8,011 species for the International Union for Conservation of Nature Red List of Threatened Species. We find that amphibians are the most threatened vertebrate class (40.7% of species are globally threatened). The updated Red List Index shows that the status of amphibians is deteriorating globally, particularly for salamanders and in the Neotropics. Disease and habitat loss drove 91% of status deteriorations between 1980 and 2004. Ongoing and projected climate change effects are now of increasing concern, driving 39% of status deteriorations since 2004, followed by habitat loss (37%). Although signs of species recoveries incentivize immediate conservation action, scaled-up investment is urgently needed to reverse the current trends., (© 2023. The Author(s).)

Tropidonotus nicobarensis Sclater, 1891 is an enigmatic snake currently referred to the natricine genus Hebius Thompson, 1913. No specimens have been recorded since the original discovery of the name-bearing type in the late 19th century, which was allegedly collected on Kamorta Island in India's Nicobar Archipelago. Recently, a second observation of this species was reported from Havelock Island (Swarajdweep) in the nearby Andaman Archipelago. However, the snake in question is clearly conspecific with another natricine, Thamnophis saurita (Linnaeus, 1766), native to eastern North America. This discovery prompted us to examine the type specimen of Tropidonotus nicobarensis, which revealed that it too is conspecific with Thamnophis saurita. The provenance of the Tropidonotus nicobarensis type specimen and the Havelock Island snake are discussed, with the latter likely representing an introduced animal.

Species of the agamid genus Bronchocela Kaup, 1827 in the Andaman and Nicobar Islands are reassessed based on newly collected specimens from different parts of the Nicobar Archipelago. An assessment based on morphology and distribution of the identified groups reveal two new, unnamed populations, one allied to B. cristatella and the other allied to B. danieli. These two populations are described as new species, and Bronchocela cristatella is redescribed based on Sundaic specimens. The remaining species, B. danieli and B. rubrigularis are redescribed. Distributions of all of these four species are mapped and recommendations on their conservation status are suggested.

The snake fauna of the Andaman archipelago was studied over a duration of four years across twenty islands. This paper presents information on the species richness and taxonomy of snakes of the Andaman archipelago along with observations on natural history and a review of their distribution records, including new, precise ones. Natural history observations for some of the recently re-evaluated species are presented herein for the first time. Field observations on snakes made during this study are supplemented with a compilation of data from specimen collections (n=34) examined in various museums. Based on this dataset and reliable, verified literature records, distribution maps are presented for all the snake species in the Andaman Islands. In addition, unsubstantiated old records of certain species that are shown to be ambiguous are removed from the updated checklist presented here, which consists of 23 species from 22 genera and eight families. Nine of these terrestrial (non-marine) species (56%) are endemic to the Andaman Islands. However, some of the non-endemic species are still in need of a proper molecular taxonomic assessment. The majority (70%) of species are of Least Concern, with 13% of the species being Data Deficient, 9% being Endangered, 5% of the species still in need of evaluation of their conservation status and 4% each being Near Threatened and Vulnerable.

We revisit the identities of Trimeresurus albolabris records from India and Nepal, based on a re-examination of historically mentioned specimens. Based on morphological congruence, we identify an old specimen originally labeled as T. albolabris from Nagpur, Central Province as Trimeresurus salazar. We also provide new records of T. salazar based on molecular data from newly collected specimens in Central India. As the range of T. salazar is now known to approach that of its sister species Trimeresurus septentrionalis, we also redescribe T. septentrionalis based on the holotype and referred material. Finally, we examined two historical specimens from Madras collected during the Novara Expedition, which we identify as T. davidi, leading to a reassessment of their origin. Consequently, we remove T. albolabris from the list of Indian snake fauna.

Recent studies on frogs of the Microhyla heymonsi species complex have demonstrated that high genetic variation exists among its various known populations from regions across Asia. We assessed the taxonomic identity of the Nicobar population of Microhyla cf. heymonsi and compared it to the typical Microhyla heymonsi from Taiwan and the two recently described species in this complex from Vietnam. Our study demonstrates that the Nicobar population is both genetically and morphologically divergent and warrants recognition as a new species, which we formally describe here as Microhyla nakkavaram sp. nov. The new species is closely related to M. daklakensis , M. heymonsi , and M. ninhthuanensis , but diagnosable from all three species by a suite of morphological characters, such as the presence of two small tubercles at mid-dorsum along with ( )-shaped markings, length of finger I longer than half the length of finger II, presence of three distinct metacarpal tubercles on hand, rudimentary foot webbing, as well as its slender body shape, granular dorsal skin texture, and other colour characters and body markings. Statistical analyses based on multiple morphometric characters also clearly separate our new taxon from M. heymonsi , with which it was previously confused. Our phylogenetic analyses based on the mitochondrial 16S rRNA locus find Microhyla nakkavaram sp. nov. to be nested in the Microhyla achatina species group, where it is delimited as a distinct species. This lineage shows genetic distances of ≥ 3.5% from all the other known congeners. Currently, the known distribution of the new taxon is restricted to the southernmost group of Nicobar Islands-Great Nicobar, Kondul, and Little Nicobar-where it is found in abundance across a wide range of habitats during the monsoon season. Our study underlines the need to reassess the identity of all the known populations of M. ' heymonsi ' from other regions in Southeast and East Asia. To facilitate future taxonomic work in the light of our and other recent findings, we also provide a detailed redescription and revised diagnosis for M. heymonsi based on morphological examination of its century-old type material originating from Taiwan.

We conducted a taxonomic revision of the arboreal snakes of the Boiga ceylonensis-group, all inhabiting the Indian subcontinent. Based on 15 characters, recorded from more than 100 specimens, representing eight recognized taxa, we conducted a multivariate morphometric analysis to redefine the taxonomic boundaries. We provide redescriptions of the nominate taxa in this group based on re-examination of the name-bearing types. The types of B. ceylonensis, B. beddomei, B. barnesii, B. dightoni, B. nuchalis and B. andamanensis are redescribed, where appropriate lectotypes are selected, illustrated and their nomenclature, synonymy and distribution are discussed. Status of the nominate taxon Boiga ceylonensis dakhunensis Deraniyagala, 1955 is fixed as an objective junior synonym of Dipsas nuchalis Günther, 1875. An updated key to the species of this group is presented.

The frog family Ranixalidae is endemic to the Western Ghats of Peninsular India and contains two genera, Indirana and Walkerana. The three known species of Walkerana are restricted to different hill ranges south of the Palghat Gap, an ancient valley in the Western Ghats. In this study, we report the discovery of a deeply divergent lineage of Walkerana from the high elevations of the Elivalmalai hill range. This finding extends the geographic range of the Walkerana clade to the north of the Palghat Gap. The new species Walkerana muduga sp. nov. is genetically and morphologically divergent, and geographically isolated from its sister lineages. We also recovered a potential new lineage in the adjoining hill ranges suggesting the presence of additional new species in this genus north of the Palghat Gap.

Tiliqua bibronii was described by J.E. Gray in December, 1838 based on two syntypes (MNHN-RA 2940, 7076), but the details for locality was missing. These syntypes are currently housed at the Muséum national d'Histoire naturelle, Paris, France (MNHN-RA). The same species (based on the same type specimens) was described by A.M.C. Duméril & G. Bibron in November, 1839 nearly one year after Gray's publication. As such, Gray's publication must therefore be given priority. Another species, Euprepis trilineatus, from Madras, Tamil Nadu, India, was described by Gray in 1846, and it is morphologically similar to E. bibronii. Later, Boulenger (1885) synonymised it with E. bibronii. Eutropis bibronii has subsequently been recorded from other parts of India and Sri Lanka by various authors. Many years later, a closely related species, Mabuya nagarjuni (sic) Sharma, 1969, was described from Andhra Pradesh, India, based on two specimens (a holotype and a paratype) housed at the Zoological Survey of India, Kolkata (ZSI). Here we make a correction for the species epithet as "nagarjunensis" which should be a toponym, not a patronym. Among the skink collections at the Natural History Museum, London (BMNH), ZSI, and MNHN-RA we found E. bibronii specimens collected from various locations in India, but we were unable to find any specimens from Sri Lanka. Based on morphological evidence, E. bibronii represents a single, fairly widespread, species which has to be considered endemic to India. Although, recent phylogenetic studies reveal a distinct genetic divergence between E. bibronii and E. nagarjunensis, both species are morphologically very similar to each other. Here, we examine the morphology of E. nagarjunensis based on the ZSI specimens. A comprehensive comparison between the syntypes of E. bibronii and Euprepis trilineatus confirms that the latter nomen is a junior synonym of the former. The original description of E. bibronii is extremely concise and lacks most of the important diagnostic characters, so here we provide a comprehensive redescription of the species based on the examination of its syntypes.

Euprepes beddomei was described by Jerdon (1870) from "Mysore" (Karnataka State, India). Simultaneously, Euprepes (Tiliqua) septemlineatus, which is morphologically similar to E. beddomei, was described by Blanford (1870) based on a single specimen collected from the Ganga River Valley, Southeast Berar, Madhya Pradesh, India. Smith (1935) synonymised the latter species (published in September, 1870) with Euprepes beddomei which in turn was published earlier (March, 1870). Jerdon's publication should therefore be given priority. A comprehensive comparison between the holotypes of the above two species confirms that E. septemlineatus is a junior synonym of E. beddomei. Based on morphological characters, Eutropis beddomei is here clearly identified and can be considered a widespread species in India and Sri Lanka. The original description of E. beddomei is very short and lacks a description containing most of the important diagnostic characters; hence, we hereby provide a comprehensive description of the species based on the examination of its holotype.

A new bufonid amphibian, belonging to a new monotypic genus, is described from the Andaman Islands, in the Bay of Bengal, Republic of India, based on unique external morphological and skeletal characters which are compared with those of known Oriental and other relevant bufonid genera. Blythophryne gen. n. is distinguished from other bufonid genera by its small adult size (mean SVL 24.02 mm), the presence of six presacral vertebrae, an absence of coccygeal expansions, presence of an elongated pair of parotoid glands, expanded discs at digit tips and phytotelmonous tadpoles that lack oral denticles. The taxonomic and phylogenetic position of the new taxon (that we named as Blythophryne beryet gen. et sp. n.) was ascertained by comparing its 12S and 16S partial genes with those of Oriental and other relevant bufonid lineages. Resulting molecular phylogeny supports the erection of a novel monotypic genus for this lineage from the Andaman Islands of India.

The Asian pitviper currently identified as Trimeresurus labialis Fitzinger in Steindachner, 1867 is revised on the basis of morphological data obtained from 37 preserved specimens originating from seven islands of the Nicobar Islands. Multivariate analyses shows that these specimens can be divided into two clusters of populations which differ by a series of constant taxonomically informative morphological characters. The first cluster, which includes the name-bearing types of Trimeresurus labialis Fitzinger in Steindachner, 1867, is present only on Car Nicobar Island. The second cluster, which includes the name-bearing types of Trimeresurus mutabilis Stoliczka, 1870, is distributed on the Central Nicobar Islands. We regard these clusters as distinct species, which are morphologically diagnosable and isolated from each other. As a consequence, Trimeresurus mutabilis, long considered a synonym of T. labialis, is here resurrected to specific level. A lectotype is designated for Trimeresurus mutabilis.