The extinct group of flying reptiles that lived alongside dinosaurs was the pterosaurs. Pterosaurs were the first vertebrates known to evolve powered flight, using wings made from a membrane of skin, muscle, and other tissues.
They lived from the Late Triassic Period until the end-Cretaceous mass extinction, roughly 228 to 66 million years ago. Although they shared prehistoric ecosystems with dinosaurs, pterosaurs were not dinosaurs. They belonged to a separate branch of the reptile family tree and were more closely related to dinosaurs and crocodilians than to modern lizards.
Pterosaur wings were supported mainly by an elongated fourth finger. Their bodies varied enormously in size: some species were small enough to fit in a person's hand, while giant azhdarchids such as Quetzalcoatlus had wingspans comparable to a small airplane. Many probably flew actively, while some large forms may have spent considerable time walking on all four limbs.
Bats and birds are also flying vertebrates, but they evolved flight independently and are not pterosaurs. Insects are flying invertebrates, lacking backbones entirely.