Definition of monotreme in English:

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Pronunciation: /ˈmänəˌtrēm/


A primitive mammal that lays large yolky eggs and has a common opening for the urogenital and digestive systems. Monotremes are now restricted to Australia and New Guinea, and comprise the platypus and the echidnas.
  • Order Monotremata and subclass Prototheria: two families.
Example sentences
  • There are only three living monotremes, the duck-billed platypus and two species of echidna, or ‘spiny anteaters’, such as the one shown at right.
  • Placental and marsupial mammals are more closely related to one another than to the third living group of mammals, the monotremes.
  • The Australian fossil record of monotremes also includes some quite good Miocene and Pleistocene fossils of giant echidnas.


Mid 19th century: from mono- 'single' + Greek trēma 'hole'.

For editors and proofreaders

Syllabification: mon·o·treme

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