The limbless, primarily soil-dwelling and tropical caecilian amphibians (Gymnophiona) comprise the least known order of tetrapods. On the basis of unprecedented extensive fieldwork, we report the discovery of a previously overlooked, ancient lineage and radiation of caecilians from threatened habitats in the underexplored states of northeast India. Molecular phylogenetic analyses of mitogenomic and nuclear DNA sequences, and comparative cranial anatomy indicate an unexpected sister-group relationship with the exclusively African family Herpelidae. Relaxed molecular clock analyses indicate that these lineages diverged in the Early Cretaceous, about 140 Ma. The discovery adds a major branch to the amphibian tree of life and sheds light on both the evolution and biogeography of caecilians and the biotic history of northeast India-an area generally interpreted as a gateway between biodiversity hotspots rather than a distinct biogeographic unit with its own ancient endemics. Because of its distinctive morphology, inferred age and phylogenetic relationships, we recognize the newly discovered caecilian radiation as a new family of modern amphibians.

Despite renewed interest in the biogeography and evolutionary history of Old World tree frogs (Rhacophoridae), this family still includes enigmatic frogs with ambiguous phylogenetic placement. During fieldwork in four northeastern states of India, we discovered several populations of tree hole breeding frogs with oophagous tadpoles. We used molecular data, consisting of two nuclear and three mitochondrial gene fragments for all known rhacophorid genera, to investigate the phylogenetic position of these new frogs. Our analyses identify a previously overlooked, yet distinct evolutionary lineage of frogs that warrants recognition as a new genus and is here described as Frankixalus gen. nov. This genus, which contains the enigmatic ‘Polypedates’ jerdonii described by Günther in 1876, forms the sister group of a clade containing Kurixalus, Pseudophilautus, Raorchestes, Mercurana and Beddomixalus. The distinctiveness of this evolutionary lineage is also corroborated by the external morphology of adults and tadpoles, adult osteology, breeding ecology, and life history features.

A new frog species of the genus Microhyla (Anura, Microhylidae) is described from riparian mid-elevation (860 m asl) evergreen forest in Namdapha National Park, located in the eastern Himalayan state of Arunachal Pradesh, India. The new species can be morphologically distinguished from other congeners by a suite of characters such as adult size, dorsal and lateral colouration and markings, snout shape, foot webbing, and digit tip morphology. Phylogenetically, the new species is more closely related to some of the smallest known members of the genus. It forms a deeply divergent sister lineage to the clade containing members of the Microhyla zeylanica species group that are restricted to Peninsular India and Sri Lanka, and shows sequential relationship with Southeast Asian species M. superciliaris, followed by clade containing M. aurantiventris + M. butleri. The discovery indicates that novel taxa representing distinct evolutionary lineages still remain to be formally described in the genus Microhyla, especially from less explored regions such as the eastern Himalayan forests in Northeast India.

The Megophrys major species group (MMSG) is composed of typically medium to large sized frogs. Within the genus, it is the most geographically widespread clade ranging from the western Himalayas to southern Indochina. In this study, we examined in detail the extent of cryptic diversity within the MMSG-Indian populations based on molecular data (up to ten genes) using multigene concatenation and coalescent-based phylogenetic techniques, species delimitation analyses and extensive morphological data.Molecular evidence suggests a high level of hidden cryptic diversity within the MMSG, particularly within the M. major species complex (MMC), highlighting overlapping distributions, a case of potential mitochondrial transfer between two species, and tree topology discordance between phylogenetic methods and mitochondrial and nuclear data sets. Most analyses indicated distinct eastern and western clades in the MMC, and that the western clade may further divide into a northern and a southern subclade.A detailed taxonomic review of Indian members of the Megophrys major species group is provided. Previously undocumented complex nomenclatural issues involving known species are highlighted and resolved. Megophrys monticola is taxonomically redefined for the first time as a valid species since its synonymy with M. parva in 1893. The taxonomic status of two recently described species, Xenophrys katabhako and X. sanu are discussed in light of increased molecular and morphological sampling, and are synonymised with M. monticola. Megophrys monticola and M. robusta are redescribed based on their original type specimens and recently collected material. Megophrys major is neotypified and M. robusta lectotypified to remove prevailing nomenclatural instability. Four new large sized Indian MMC species are formally described from the Northeast Indian states of Arunachal Pradesh, Meghalaya and Nagaland, and Myanmar. All South Asian MMSG species are morphologically diagnosed from known congeners in the group. The geographic distributions of all taxa discussed are significantly redefined based on the revised taxonomy and extensive literature review. Morphological and molecular evidence suggests that Megophrys major sensu stricto might be endemic to Northeast India; M. glandulosa is formally removed from the Indian and Bhutan species checklists. Numerous misidentifications in literature are highlighted and corrected. In order to reduce future misidentifications of species reported from surrounding regions, high definition images of the holotypes of three Chinese species, M. glandulosa, M. medogensis and M. zhangi are provided for the first time, and a detailed description of Myanmar specimens of M. glandulosa is also given. This study provides the principle foundation for further research into the taxonomic status of the remaining, currently undescribed MMC taxa from Southeast Asia.