The platypus and the echidna are egg-laying mammals.

鸭嘴兽和针鼹是产卵哺乳动物。

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They are the only two egg-laying mammals in the world.

它们是世界上唯一的两种产卵的哺乳动物。

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Today, this bizarre but fascinating creature is known as the platypus, one of only five extant monotremes (egg-laying mammals).

如今，这种怪诞但迷人的生物被命名为鸭嘴兽，现存的五种卵生哺乳动物之一。

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Echidnas are part of a group of egg-laying mammals called monotremes.

VOA: special.2009.07.07

Two long-beaked echidnas, primitive egg-laying mammals, even allowed scientists to pick them up and bring them back to their camp to be studied, he added.

BBC: NEWS | Science/Nature | Science team finds 'lost world'