monotreme

American  

[mon-uh-treem] / ˈmɒn əˌtrim /

noun

1. any animal of the Monotremata, the most primitive order of mammals, characterized by certain birdlike and reptilian features, as hatching young from eggs, and having a single opening for the digestive, urinary, and genital organs, comprising only the duckbill and the echidnas of Australia and New Guinea.

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monotreme British  

/ ˈmɒnəʊˌtriːm /

noun

1. any mammal of the primitive order Monotremata, of Australia and New Guinea: egg-laying toothless animals with a single opening (cloaca) for the passage of eggs or sperm, faeces, and urine. The group contains only the echidnas and the platypus

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monotreme Scientific  

/ mŏn′ə-trēm′ /

1. Any of various mammals of the order Monotremata. Monotremes are the most primitive type of living mammal. They lay eggs and have a single opening (cloaca) for reproduction and elimination of wastes. The females have no teats but provide milk directly through the skin to their young. The only living monotremes are the duck-billed platypus, found in Australia and New Guinea, and the echidnas, found in New Guinea. Monotremes may have evolved already in the Jurassic Period, but the precise nature of their relationship to marsupials and placental mammals is disputed.

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Other Word Forms

• monotrematous
  adjective

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Etymology

Origin of monotreme

1825–35; < French monotrème < New Latin monotrema, assumed singular of Monotremata, neuter plural of monotrematus monotrematous

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Example Sentences

See Examples For:

monotreme

Its ecosystem included frogs, lizards, turtles, and mammals such as Patagorhynchus pascuali, a semi aquatic monotreme related to modern echidnas and platypuses.

From Science Daily ● May 29, 2026

They take the total number of monotreme species known to have once lived at Lightning Ridge - which was in ancient times a cold, wet forest bordering a vast inland sea - to six.

From BBC ● May 27, 2024

Besides the duck-billed platypus, echidnas are the only other surviving monotreme: an ancient type of mammal that lays eggs.

From Slate ● Jan. 28, 2023

Resembling a pug-size hedgehog with the schnoz of an anteater, they are one of only five living species of monotreme, that rare mammal that lays eggs.

From Science Magazine ● Jan. 17, 2023

That bone is known in a separate state in reptiles and, I think, in monotreme mammals.

From Dragons of the Air An Account of Extinct Flying Reptiles by H. G. Seeley

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