A Moment of Science

Those Mystifying Mammals, the Monotremes

Have you heard that the long-beaked echidna, which scientists thought was extinct, has been found again in New Guinea? Learn more on this Moment of Science.

Young Echidna

Photo: ausemade (flickr)

Echidnas like this one in Australia belong to a group called the Monotremes, which have mammal characteristics but also lay eggs

Have you heard that the long-beaked echidna, which scientists thought was extinct, has been found again in New Guinea?

The echidna is one of only five living species of Monotremes, an order of mammals that lay eggs rather than giving birth to live young, like all other mammals do. Modern monotremes are toothless, have leathery or bird-like beaks, and like birds and reptiles, they have only a single opening through which they lay eggs and eliminate waste.

Why then are they considered mammals you may be wondering?

Like other mammals, monotremes are warm-blooded. They have hair on their bodies and produce milk to feed their young.

In echidnas, the female lays eggs into a pouch of skin on her stomach, where she carries them until they hatch. Although they have mammary glands, monotremes do not have nipples like other mammals. Instead, milk is released through pores in the skin and the young suckle from these milk patches until they are mature enough to fend for themselves.

The current school of thought holds that monotremes come from a lineage of mammals that branched off the mammalian family tree over two-hundred million years ago, and have been evolving independently from the rest of the earth’s mammals ever since. Scientists are currently working on sequencing the platypus genome, which could shed more light on the evolutionary history of these mystifying animals.

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