The water opossum (Chironectes minimus), also locally known as the yapok , is a marsupial of the family Didelphidae. It is the only member of its genus, Chironectes. This semiaquatic creature is found in and near the freshwater streams and lakes in Mexico, Central and South America to Argentina, and is the most aquatic living marsupial (the lutrine opossum also has aquatic habits). It is also the only living marsupial in which both sexes have a pouch. The thylacine, commonly referred to as the Tasmanian tiger, also exhibited this trait, but is now believed to be extinct.