monotreme

n. animal which belongs to the family of egg laying mammals found in Australia (Zoology)

Monotremes (from the Greek monos 'single' + trema 'hole', referring to the cloaca) are mammals that lay eggs instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria).They are conventionally treated as comprising a single order Monotremata, though a recent classification proposes to divide them into the orders Platypoda (the platypus) and Tachyglossa (the echidnas). The entire grouping is also traditionally placed into a subclass Prototheria, which was extended to include several fossil orders but these are no longer seen as constituting a natural group allied to monotreme ancestry. A controversial hypothesis now relates the monotremes to a different assemblage of fossil mammals in a clade termed Australosphenida.
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Noun
1. the most primitive mammals comprising the only extant members of the subclass Prototheria
(synonym) egg-laying mammal
(hypernym) prototherian
(hyponym) echidna, spiny anteater, anteater

n. Monotremata, order of Australian egg-laying mammals (Zoology)

(n.)
One of the Monotremata.