Gastric-Brooding frogs are a pretty cool group of frogs. There are only 2 species of them in their genus Rheobatrachus. They are members of the family Myobatrachidae, and part of the advanced frogs sub-order Neobatrachia. They were native to Australia.
The reason why this group of frogs are so interesting is because the female swallows their pre juvenile off spring and incubates them in their stomach until they are grown enough to live on their own. The eggs have a gel surrounding them that stop the acid in the mother’s stomach from digesting them.
A group of researchers are trying to revive the species from extinction. The program is called the Lazarus project. They hope to bring back the species by cloning them from 40 year old samples of DNA that were preserved.