Little is known about the reproductive biology of species of the genus Melanophryniscus. This study provides the first description of amplexus behaviour, egg-laying sites, clutch characteristics and larval development of Melanophryniscus sp., a species of uncertain taxonomic status that is found in the southernmost range of the genus (Sierra de la Ventana, Argentina), and their relationship with habitat features and selection pressures is discussed. Results are compared with the reproductive biology of other species in the genus.