Pterosaurs are derived archosaurs that evolved flight. Their evolution of flight was seperate from the evolution of flight in other vertebrates like the birds, or the mammalian fliers like bats. Pterosaurs were spectacular fliers, with the pterodactyloids having wing spans from eleven to twelve meters long (close to thirty six feet). The wings main support was an amazingly elongated fourth digit in the hand. Fibers in the wing membrane added structural support and stiffness.
