Compared to saurischian and ornithischian dinosaurs and marine reptiles, the classification of pterosaurs ("winged lizards") is a relatively straightforward affair. These reptiles all belong to a single order, which is itself divided into two suborders (only one of which is a "true" suborder in evolutionary terms).
Order: Pterosauria Pterosaurs--almost certainly the first large animals on earth ever to evolve flight--were characterized by their hollow bones, relatively large brains and eyes, and, of course, the flaps of skin extending along their arms, which were attached to the digits on their front hands.Suborder: Rhamphorhychyinoidea In legalistic terms, this suborder has a shaky status, since it's believed that the pterodactyloidea (described below) evolved from creatures in this group, rather than both groups having evolved from a common ancestor. Whatever the case, paleontologists often assign smaller, more primitive pterosaurs--such as Rhamphorhynchus and Anurognathus--to this group. Rhamphorhynchoids are characterized by their teeth, long tails, and (in most cases) lack of skull crests, and lived during the Triassic period.
Suborder: Pterodactyloidea This is the only "true" subgroup of pterosauria; it includes all the large, familiar flying reptiles of the Jurassic and Cretaceous periods, including Pteranodon, Pterodactylus, and Quetzalcoatlus. Pterodactyloids were characterized by their relatively large size, short tails and long hand bones, as well as (in some species) elaborate, bony head crests and lack of teeth. These pterosaurs survived up until the K/T Extinction 65 million years ago, when they were wiped out along with their dinosaur and marine reptile cousins.