Marsupials are an infraclass of mammals living primarily in the Southern Hemisphere. A distinctive characteristic, common to most species, is that the young are carried in a pouch. Well-known marsupials include kangaroos, wallabies, the koala, possums, opossums, wombats and the Tasmanian devil. Less well-known species of marsupials include the numbat, bandicoots, bettongs, the bilby and quolls. No marsupials can be found in Africa, Asia, or Europe, with the exception of a feral population of wallabies that escaped from a zoo in England. Marsupials are non-placental and give birth to premature young, which grab hold of the mother's nipple right after birth. In most species, the young can be found in a special pouch or fold of skin located on the back or belly. Marsupials have small brains compared to their body and are not considered to be very intelligent.