A member of the Monotremata, an order of primitive egg-laying mammals restricted to Australia and New Guinea and consisting of only the platypus and the echidna.

• 单孔目动物单孔目动物中的一员，是远古蛋生哺乳动物的一目，限生活于澳大利亚和新几内亚地区，只有鸭嘴兽和针鼹种类