Monotremata

Monotremes are mammals that are best known for laying eggs, instead of giving birth to their young like marsupials and eutheria?s.

The word monotreme comes from the Greek words mono- and trema, meaning one and hole. The one hole refers to the fact that monotremes have a single opening for the urinary, digestive and reproductive organs.

Like other mammals, monotremes

• are "warm-blooded?" with high metabolic rates
• have hair on their bodies
• produce milk to feed their young
• have a single bone in their lower jaw
• have three inner ear bones

The only surviving examples are all indigenous to Australia and New Guinea:

• Platypus has only one genus comprising one species: Ornithorhynchus anatinus.
• Echidna, or spiny anteaters, have two genuses with several species each: Tachyglossus and Zaglossus.

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External link:

University of Tasmania's monotreme web site at http://www.healthsci.utas.edu.au/physiol/mono/Monotremata.html.