Patagopteryx deferrariisi

Patagopteryx is an extinct monotypic genus of euornithean dinosaurs that lived during the Late Cretaceous, around 80 mya, in what is now the Sierra Barrosa in northwestern Patagonia, Argentina. About the size of a chicken, it is the earliest known unequivocal example of secondary flightlessness: its skeleton shows clear indications that the ancestors of Patagopteryx were flying animals, though other studies find earlier diverging theropods to be secondarily flightless.