The four original specimen of Nanorana arnoldi, Arnold’s paa frog, were collected by R. Kaulback on expedition in 1930 in Pangnamdim, northern Myanmar (at 910 m asl). However the specimens were incorrectly reported as Rana feae (Smith 1940).In later analysis, Dubois (1975) recognized these as distinct from R. feae.He characterized the differences and described "Rana arnoldi" as a species nova, and named it for E.N. Arnold, of the British Museum of Natural History.Although N. arnoldi has subsequently been collected in southern China (Xizang Autonomous Region and north-western Yunnan Province), N. arnoldi has not been reported again in Myanmar.In China, it is uncommon, found in small forested streams and springs near paddy fields.Locals collect it (and other species in its genus) for food, presenting a significant threat to this species.Arnold's paa frog is further threatened by habitat degradation and development for agriculture.
This species may also include Paa chayunensis (Liang et al. 2004).