Where does embryonic development occur in mammals?

1 Answer

Mammals are separated into three groups. 1. Prototheria (before gestation) - egg laying mammals, 2. Metatheria (middle gestation) - pouched mammals and 3. Eutheria (true gestation) - live birth from uterus.


  1. In Prototherian mammals embryonic development occurs in egg. They’re egg laying mammals (oviparous).

  2. In Metatherian mammals embryo starts it’s development within the mother’s uterus, supported by a short-lived placenta. A marsupial is born very early in its development. It complete it’s embryonic development while nursing in a maternal pouch called marsupium. They’re viviparous.

  3. In Eutherian mammals embryo complete its embryonic development in uterus, joined to the mother by placenta. Eutherians have a longer period of pregnancy when compared to metatherians. They’re viviparous.

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