Abstract
A new species of small tree frog is described from northwestern Vietnam based on morphological differences and molecular divergence. Gracixalustruongisp. nov. is distinguishable from its congeners and other small rhacophorid species on the basis of a combination of the following characters: size relatively small, SVL 32.2-33.1 mm in males, 37.6-39.3 mm in females; head slightly wider than long; vomerine teeth absent; snout round and long RL/SVL 0.17-0.19 in males, 0.16-0.17 in females; spines on upper eyelid absent; supratympanic fold distinct; tympanum distinct; dorsal skin smooth; throat smooth and venter granular; tibiotarsal projection absent; webbing of fingers rudimentary, toes with moderately developed webbing; dorsum moss-green, with an inverse Y-shaped dark green marking extended from interorbital region to posterior region of dorsum; external vocal sac absent in males; males with a nuptial pad on finger I. In the molecular analyses, the new species has no clear sister taxon and is at least 4.5% divergent from other congeners based on a fragment of the mitochondrial 16S rRNA gene.