Borneo Narrow-Mouthed Frog

Microhyla borneensis (junior synonym Microhyla nepenthicola), also known as the Matang narrow-mouthed frog, is a species of microhylid frog found in the Matang Range in Sarawak, Borneo. It was once the smallest known frog from the Old World (since 2012, the record holder has been Paedophryne amauensis from New Guinea). Adult males of this species generally have a snout–vent length (SVL) in the range of 10.6–12.8 mm (0.42–0.50 in), but may reach a maximum of 13 mm (0.51 in). Adult females have an SVL of 16–19 mm (0.63–0.75 in). The tadpoles measure just 3 mm.

Microhyla borneensis was first described by Hampton Wildman Parker in 1928. Frogs of the species that was eventually described as Microhyla nepenthicola had been known for at least 100 years prior to its description in 2010. However, scientists had always assumed that the frogs were juveniles of another species. Researchers Indraneil Das and Alexander Haas recognized that they were actually adults when they heard the frogs calling in Kubah National Park, since only adult frogs make calls. Adult males call from the pitcher plants at dusk. However, in 2011 it was shown that M. borneensis and M. nepenthicola are the...