There are only three living monotremes, the duck-billed platypus and two species of echidna, or "spiny anteaters", such as the one shown at right. All of them are found only in Australia and New Guinea. Monotremes are not a very diverse group today, and there has not been much fossil information known until rather recently.

In some ways, monotremes are very primitive for mammals because, like reptiles and birds, they lay eggs rather than having live birth. In a number of other respects, monotremes are rather derived, having highly modified snouts or beaks, and modern adult monotremes have no teeth. Like other mammals, however, monotremes have a single bone in their lower jaw, three inner ear bones, high metabolic rates, hair, and they produce milk to nourish the young.

Read about monotremes at the University of Tasmania, who have one of the best sites on the web about living monotremes.

Try the University of Michigan's Animal Diversity Web for more information about living monotremes. The Tasmanian Mammals page includes distributional information on monotremes.

Threatened Species of Australia maintains a platypus bibliography, or you can visit Lightspan Study Web for more information on the platypus.

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