Pterosaurs (/ˈtɛrəsɔːr, ˈtɛroʊ-/; from Greek pteron and sauros, meaning "wing lizard") were flying reptiles of the extinct clade or order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to 66 million years ago).