In South America, marsupials and placentals shared the ecosystem (prior to the Great American Interchange); in Australia, marsupials prevailed; and in the Old World and North America the placentals won out.
En Suramérica, os marsupiais e os placentarios compartiron o ecosistema (antes da conexión entre América do Norte e do Sur); en Australia, os marsupiais prevaleceron; e no Vello Mundo os placentarios foron os vencedores.