• Question: Hi! why do platypuses lay eggs even though they are mammals?

    Asked by Lilymarie to Angela on 12 Nov 2014.
    • Photo: Angela Stokes

      Angela Stokes answered on 12 Nov 2014:

      Hi lilymarie

      This is to do with how mammals developed
      There are three types of mammal.
      – placental who reproduce like people
      – marsupials like kangaroos who have a brief pregnancy and result in tiny babies who continue their development in a pouch
      – monotremes who are egg laying mammals. These are a kind of cross between a mammal and a reptile and developed in the late Permian and early Triassic period which is when a split between mammals and reptiles occurred. This ‘cross’ group is very rare and apart from platypuses I can only think of one other – the echidna. Although they lay eggs they are considered mammals because they have fur and produce milk.

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