A new litter frog: Leptolalax isos

Litter frogs are a large family of frogs native to the warm southeast of Asia. The group contains at least 180 species. Litter frogs are notable for their camouflage, especially those that live in forests, which often look like dead leaves, hence the name litter frog referring to leaf litter. The camouflage is accurate to the point of some having skin folds that look like leaf veins, and at least one species, the long-nosed horned frog (Megophrys montana) has sharp projections extending past the eye and nose, which disguise its frog shape.

The genus Leptolalax is widely distributed in southeastern and eastern Asia and comprises of typically small frogs with a cryptic colour pattern and no obvious morphological characters. The new species was found on the Kon Tum Plateau of Vietnam and adjacent Cambodia. Its name was derived from the Greek word isos, meaning equal or like, in reference to the similarity of the

new species to another congener Leptolalax firthi.

For the experts: We describe a new, medium-sized Leptolalax species from the Kon Tum Plateau of Vietnam and adjacent Cambodia. Leptolalax isos sp. nov. is distinguished from its congeners by a combination of an absence of distinct dark brown/black dorsolateral markings; toes with rudimentary webbing, wide lateral dermal fringes in males and weak or absent lateral dermal fringes in females; most males with wide lateral dermal fringes on Finger II, a body size of 23.7–27.9 mm in 38 adult males and 28.6–31.5 mm in 9 adult females, near immaculate white chest and belly; absence of white speckling on the dorsum; and a call consisting of 2–3 notes with a dominant frequency of 5.9–6.2 kHz (at 22.4–22.8º C). Uncorrected sequence divergences between L. isos sp. nov. and all homologous 16S rRNA sequences available are >10%. At present, the new species is known from montane evergreen forest between ~650–1100 m elevation in northeastern Cambodia and central Vietnam. Habitat within the range of the new species is threatened by deforestation and upstream hydroelectric dams.