Monotremes (from the Greek μονός monos "single" + τρῆμα trema "hole", referring to the cloaca) are mammals that lay eggs (Prototheria) instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). The only surviving examples of monotremes are all indigenous to Australia and New Guinea, although there is evidence that they were once more widespread. Among living mammals they include the platypus and four species of echidnas (or spiny anteaters); there is debate regarding monotreme taxonomy. The young of a monotreme is sometimes called a puggle.