The brown four-eyed opossum (Metachirus nudicaudatus) is a pouchless marsupial of the family Didelphidae. It is found in different forested habitats of Central and South America, from Nicaragua and to Paraguay and northern Argentina, at elevations from sea level to 1500 m. It is the only recognized species in the genus Metachirus, but molecular phylogenetics studies suggest that it should probably be split into several species. Population densities are usually low, and it is uncommon in parts of Central America. A density of 25.6/km2 was reported near Manaus, Brazil. Its karyotype has 2n = 14 and FN = 24.