Type species. Telmatobius grandisonae Lynch, 1975

Content. The genus is monotypic

Definition and diagnosis. Size small to medium, up to 46 mm SVL. Dorsal coloration uniform bright green, with brown to reddish warts. Dorsal skin thin and mucoid, finely granulated. Iris orange. Vomerine teeth in two patches between and at posterior level of the choana. Tympanum and columella absent. Fingers with evident interdigital membrane. Plantar skin turgid with low metatarsal tubercles. Supernumerary palmar and plantar tubercles absent. Length of toes in increasing order: 1–2–5–3–4. Frontoparietals moderately extensive, exposing a thin frontoparietal fontanelle. Nasals relatively small, separated medially. Independent quadratojugal absent. Alary processes of premaxillae extensive, directed dorsally. Maxillary teeth extending up to the middle of the orbit. Palatines relatively long, reaching the maxilla, bearing well developed anterior processes. Sphenethmoid well ossified, extending anteriorly beyond the anterior edge of nasals. Cotylar facets of atlas narrowly separated. Transverse processes of posterior presacral vertebrae slightly shortened. Omosternum cartilaginous, elongate, with anterior end expanded. Inner metacarpal with a distinct distal flange at the medial margin of the bone. Terminal phalanges knobbed, not T–shaped. Tadpole with ventral and lateral skin transparent. Anterior and lateral papillae of oral disc protruding from the contour of the snout in dorsal view. Chromosome number 2n = 32.

Etymology. The genus name derives from Chaltén, the name given by Tehuelche natives to the main mountain located south of Lago del Desierto, also known as Mount Fitz Roy, of 3406 m elevation.