From Embryology

Monotremes are mammals that lay eggs (Prototheria) instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). These animals have a single cloaca forming a common opening for both the urogenital and digestive systems, monotreme means "one-holed". This category includes the platypus and the echidna.


This category has the following 2 subcategories, out of 2 total.