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

We 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. [ABSTRACT FROM AUTHOR]