Discovery of a new species of dwarf frog (Anura: Ceratobatrachidae: Alcalus ) extends the northwestern distributional limits of the genus to Northeast India

AbstractWe describe a new species of the genus Alcalus from the northeast Indian state of Arunachal Pradesh based on molecular, morphological, and osteological characters. The new species differs from its congeners based on a combination of morphological characters including snout-vent length (27–28 mm in males; 29.9–36.2 mm in females), disc on fingers and toes with horizontal/transverse groove on the dorsal surface, dorsal skin wrinkled, and a pair of faint dorsolateral stripes on back. The new species also differs from its congeners by a DNA sequence divergence of 7.6–25.4% in the mitochondrial gene fragment 12S–tVal–16S rRNA (1533 base pairs). We include a detailed osteological description of the new species and compare it with the type of this genus. This is the first record of this genus from India, which was recently also reported from Myanmar and Western China. Discovery of a new species from northeast India indicates the need for a systematic study to uncover the hidden diversity of the Indo-Burma biodiversity hotspot. http://zoobank.org/urn:lsid:zoobank.org:pub:FB75F850-2AD9-4643-97CE-7F3F1D58E3F8 http://zoobank.org/urn:lsid:zoobank.org:act:6104F7A5-7E5E-42A7-90A1-810C394CFB3EKey words: Arunachal PradeshIndo-Burma biodiversity hotspotNamdapha Tiger Reserveosteologyphylogeny AcknowledgementsWe are very thankful to Arunachal Pradesh Forest Department for the research permit (CWL/GEN/355/2021/3178 dated 28 September 2021). Thanks are also due to Aduk Paron (Field Director), Tajum Yomcha (Research officer), Mayur Variya (Biologist), and all the forest staff of Namdapha Tiger Reserve for logistical support. We would like to thank the Director and Dean, Wildlife Institute of India, Dehradun for their constant support. We thank Naitik G. Patel, Vijayan Jithin, Santanu Dey, Rajiv N.V., and Aphu Yoha Yobin for their help during fieldwork. We thank Patrick Campbell, David Gower, and Jeff Streicher at NHM, London for their support. Surya thanks N.A. Aravind for his support at ATREE, Bengaluru. We thank Chinta S. for the help in editing and correcting the language in the manuscript. We thank two anonymous reviewers and the editor for their critical comments on the earlier drafts of this manuscript.Disclosure statementNo potential conflict of interest was reported by the author(s).Supplemental materialSupplemental material for this article can be accessed here: https://dx.doi.org/10.1080/14772000.2023.2249891.Associate Editor: Dr Susan TsangAdditional informationFundingWe thank the National Geographic Society for National Geographic Explorer Grant [NGS-74044R-20) and SERB-DST [CRG/2018/000790] for financial support.