The Mascarene Grass Frog is a rather big, long-legged frog with a pointed snout and distinct dorsal ridges.
The back has a uniform brown basic coloration with a bright vertebral band beginning at the snout tip.
The color of this band may be white, beige, yellow, orange or green.
Some individuals may lack this band.
Several black spots are present on the dorsal ridges.
The dark bars on the thighs are present only on the anterior part.
A thin yellow longitudinal line with black borders runs along the posterior part of the thighs.

Dr. Julian Glos of the University of Hamburg and expert on Malagasy amphibians helped me identifying this species.

Top: Mananara Lodge area, Anjozorobe, Madagascar, 17 January 2014
Left & Middle: Andasibe-Mantadia National Park, Madagascar, 15 January 2014