The single species Ornithorhynchus anatinus of the family Ornithorhynchidae in the order Monotremata, which occurs in eastern Australia and Tasmania. This mammal is a monotreme, which lays eggs and incubates them in a manner similar to birds. The platypus is also known as the duckbill, duckmole, and water mole. One of the most primitive mammals, it retains some reptilian characteristics. The female lacks a marsupium; however, marsupial or epipubic bones are well developed.