Monotreme
/ˈmɑːnətriːm/
Definition 1 of 1
Pro Tip 1/3Egg-Laying Mammals
Monotremes are unique as the only mammals that lay eggs. 
I learned that monotremes break the typical mammalian life cycle by laying eggs.
Pro Tip 2/3Rare Animals
Monotremes are extremely rare, with only two examples existing today. 
During the documentary, they showed the rare monotreme, the echidna, in its natural habitat.
Pro Tip 3/3Australian Exception
'Monotreme' often refers to animals native to Australia and New Guinea. 
If you visit an Australian zoo, ask if they have a monotreme exhibition.