A frog swallowed its own fertilised eggs and gave birth through its mouth
Australia's gastric-brooding frog raised its tadpoles inside its own stomach: a chemical in the egg jelly switched off the mother's stomach acid so the young could develop safely, then she stopped eating until they were born as fully formed froglets through her mouth. The species vanished within a decade of its 1973 description and was declared extinct by 2002; a later 'Lazarus Project' cloned its embryos, though none survived past the earliest stage.