We report on a discovery of Siamophryne troglodytes Gen. et sp. nov., a new troglophilous genus and species of microhylid frog from a limestone cave in the tropical forests of western Thailand. To assess its phylogenetic relationships we studied the 12S rRNA–16S rRNA mtDNA fragment with final alignment comprising up to 2,591 bp for 56 microhylid species. Morphological characterization of the new genus is based on examination of external morphology and analysis of osteological characteristics using microCT-scanning. Phylogenetic analyses place the new genus into the mainly Australasian subfamily Asterophryinae as a sister taxon to the genus Gastrophrynoides, the only member of the subfamily known from Sundaland. The new genus markedly differs from all other Asterophryinae members by a number of diagnostic morphological characters and demonstrates significant mtDNA sequence divergence. We provide a preliminary description of a tadpole of the new genus. Thus, it represents the only asterophryine taxon with documented free-living larval stage and troglophilous life style. Our work demonstrates that S. troglodytes Gen. et sp. nov. represents an old lineage of the initial radiation of Asterophryinae which took place in the mainland Southeast Asia. Our results strongly support the “out of Indo-Eurasia” biogeographic scenario for this group of frogs. To date, the new frog is only known from a single limestone cave system in Sai Yok District of Kanchanaburi Province of Thailand; its habitat is affected by illegal bat guano mining and other human activities. As such, S. troglodytes Gen. et sp. nov. is likely to be at high risk of habitat loss. Considering high ecological specialization and a small known range of the new taxon, we propose a IUCN Red List status of endangered for it.

We describe Cyrtodactylus saiyok sp. nov. from a dry evergreen forest on a limestone hill in Khao Krajae, Sai Yok District, Kanchanaburi Province, western Thailand. It is characterized by a maximal known SVL of 61.0 mm; 18-19 longitudinal rows of dorsal tubercles; 23 or 24 ventral scale rows between ventrolateral skin folds; a continuous series of enlarged femoro-precloacal scales, including 5 pore-bearing precloacal scales (males); no precloacal groove or depression; transversely enlarged subcaudal scales; a complete black nuchal loop; a W-shaped band above shoulders and 3-5 irregular, medially interrupted or not, black dorsal bands between limb insertions. Cyrtodactylus saiyok sp. nov. is the sixth reptile species that is possibly endemic to Sai Yok District.