Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago; their dominance continued through the Jurassic and Cretaceous periods. The fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch. As such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs are divided into two large groups, and one of them is avian (flying) dinosaurs, those who have wings and have the ability to fly. In the stamps you can see the following flying dinosaurs: Quetzalcoatlus, Tapejara wellnhoferi, Cearadactylus, Rahonavis, Dimorphodon, Cearadactylus.