The first vertebrates took to the skies sometime during the Triassic Period, about 225 million years ago. They weren’t birds, ...

Gauthier, Jacques and de Queiroz, Kevin. 2001. "Feathered Dinosaurs, Flying Dinosaurs, Crown Dinosaurs and the Names "Aves"." In New Perspectives on the Origin and Early Evolution of Birds: ...

By about 175 million years ago, a group known as Pennaraptora had emerged - the closest known relatives of modern birds and ...