1. The world's only monotremes are the platypus and the echidna.
鸭嘴兽和针鼹鼠是世界上唯一的单孔类动物。
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2. 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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3. The echidna is such a unique animal that it is classified in a special class of mammals known as monotremes, which it shares only with the platypus.
因针鼹鼠之独特，被定类为特殊的哺乳动物，属单孔类动物。单孔类动物只有针鼹鼠和鸭嘴兽。
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4. The echidna is such a unique animal that it is classified in a special class of mammals known as monotremes, which it shares only with the platypus.
