Rheobatrachus vitellinus and Rheobatrachus silus, Australia
Female gastric brooding frogs swallowed their eggs and gave birth through their mouths.
The two species of gastric brooding frog were discovered as early as 1914 in a river catchment in eastern Australia. The frogs were known for their unique mode of reproduction: females swallowed eggs and raised tadpoles in the stomach, giving birth to froglets through their mouths.
During the brooding stage, the frogs' stomachs temporarily stopped producing hydrochloric acid. This condition could have provided insight on the treatment of stomach ulcers in humans; unfortunately, both species of brooding frog are believed to be extinct. The specific causes of the frogs' decline are unknown, though the effects of timber harvesting on the local habitat were never investigated. The chytrid fungus is also suspected to have played a role in the species' disappearance.
Status: last seen in 1985 – listed as Extinct on IUCN Red List