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 marsupial (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 along with its fossil relatives) 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.An infant monotreme is known as a puggle. Monotremes are among the small number of mammalian species known to be capable of electroreception.
Like other mammals, monotremes are w