A small, variable coloured, mainly arboreal frog; males 21-29 mm, females 27-28 mm. Dorsal surface reddish, greyish or greenish often with a dark bar between the eyes and sometimes with a light vertebral median band. White or yellow spots on the inguinal region, temporal region dark and white spots on the upper lip. In life, ventral surface of the female is pale green, whereas the throat of the male is shining white. Belly and ventral surface of the legs are dark, sometimes (in specimens from Ranomafana
) completely black. Dorsal skin more or less smooth. Nostrils clearly nearer to tip of snout than to eye. Tympanum distinct, about 2/5 of eye diameter. Tibiotarsal articulation reaches the eye. Lateral metatarsalia connected. Inner and outer metatarsal tubercles present. Virtually no webbing between fingers; webbing of the foot 1(1), 2i/e(1), 3i(2), 3e(1), 4i/e(2), 5(1). Fingers with terminal disks. Hand (foot) length/SVL is 0.32-0.34 (0.46-0.50). Males have femoral glands which can be diffuse and not recognizable, especially in living specimens, but sometimes are large, oblong, 8x2.5 mm and very distinctive. A largely distensible, single subgular vocal sac, coloured bright white, is present in males.
Similar species: Colouration of M. liber is very variable; M. pulcher can be identified by its different colouration of green with violet markings. From all species of the subgenus Pandanusicola, M. liber differs by having larger hands and feet: hand length/body length ratio is 0.23-0.28, foot length/body length ratio is 0.38-0.43 for species of Pandanusicola. The connected lateral metatarsalia distinguish M. liber from the other species of Guibemantis. Confusion with members of Blommersia and with small species of Boophis, especially those of the B. rappiodes-group, might also be possible.
Taken with permission from Glaw and Vences (2007).