The Sri Lankan torrent toads (Bufonidae: Adenominae: Adenomus): species boundaries assessed using multiple criteria.

The bufonid genus Adenomus , an endemic of the montane and lowland rainforests of central and south-western Sri Lanka, has been considered to comprise of three species, viz. A. kelaartii , A. dasi and A. kandianus , the last of which has been recently highlighted as “the world’s rarest toad”. We conducted a survey across the known range of Adenomus and used multiple criteria to delineate species boundaries within the genus. These include: a molecular phylogeny based on a 16S ribosomal RNA gene fragment; an examination of the external morphology of adults and larvae, and the skeletal morphology of adults; a bioacoustic analysis; and ecological niche modelling. We show that Adenomus is monophyletic and that it comprises only two species: A. kelaartii and A. kandianus , with A. dasi being a junior synonym of the latter. For the two valid species of Adenomus , we provide detailed osteological descriptions; clarify the distribution patterns; and provide genetic data to facilitate their scientific conservation management.