Aside from their relative sizes, the pterosaurs of the Jurassic and Cretaceous periods differed from one another in two important ways: feeding habits and ornamentation. Generally, paleontologists can infer a pterosaur's diet from the size and shape of its jaws, and by looking at analogous behavior in modern birds (such as pelicans and seagulls). Pterosaurs with sharp, narrow beaks most likely subsisted on fish, while anomalous genera like Pterodaustro fed on plankton (this pterosaur's thousand or so tiny teeth formed a filter, like that of a blue whale) and the fanged Jeholopterus may have sucked dinosaur blood like a vampire bat (though most paleontologists dismiss this notion).
Like modern birds, some pterosaurs also had rich ornamentation--not brightly colored feathers, which pterosaurs never managed to evolve, but prominent head crests. For example, Tupuxuara's rounded crest was rich in blood vessels, a clue that it may have changed color in mating displays, while Ornithocheirus had matching crests on its upper and lower jaws (though it's unclear if these were used for display or feeding purposes).
Most controversial, though, are the long, bony crests atop the noggins of pterosaurs like Pteranodon and Nyctosaurus. Some paleontologists believe that Pteranodon's crest served as a rudder to help stabilize it in flight, while others speculate that Nyctosaurus may have sported a colorful "sail" of skin. It's an entertaining idea, but some aerodynamics experts doubt that these adaptations could have been truly functional.
The key trait that distinguished pterosaurs from land-bound feathered dinosaurs that evolved into birds was the nature of their "wings"-- which consisted of wide flaps of skin connected to an extended finger on each hand. Although these flat, broad structures provided plenty of lift, they may have been better suited to passive gliding than powered, flapping flight, as evidenced by the dominance of true prehistoric birds by the end of the Cretaceous period (which may be attributed to their increased maneuverability).
Although they're only distantly related, ancient pterosaurs and modern birds may have shared one important feature in common: a warm-blooded metabolism. There's evidence that some pterosaurs (like Sordes) sported coats of primitive hair, a feature usually associated with warm-blooded mammals, and it's unclear if a cold-blooded reptile could have generated enough internal energy to sustain itself in flight.
Like modern birds, pterosaurs were also distinguished by their sharp vision (a necessity for hunting from hundreds of feet in the air!), which entailed a bigger-than-average brain than that possessed by terrestrial or aquatic reptiles. Using advanced techniques, scientists have even been able to "reconstruct" the size and shape of the brains of some pterosaur genera, proving that they contained more advanced "coordination centers" than comparable reptiles.
Here's a list of the most notable pterosaurs; just click on the links for more information.
Aerotitan The first identified azhdarchid pterosaur from South Ameria.
Aetodactylus A new pterosaur from North America.
Alanqa A new pterosaur from northern Africa.
Angustinaripterus This "narrow-nostriled" pterosaur was a relative of Rhamphorhynchus.
Anhanguera This pterosaur had crests on the top and bottom of its head.
Anurognathus One of the smallest pterosaurs of prehistoric times.
Austriadactylus Guess which country this pterosaur was discovered in?
Azhdarcho A giant pterosaur from central Asia.
Bakonydraco The remains of this pterosaur were found in Hungary.
Campylognathoides A classic, long-tailed, early Jurassic pterosaur.
Caulkicephalus This pterosaur was recently discovered on the Isle of Wight.
Cearadactylus A fish-eating pterosaur from South America.
Coloborhynchus The largest toothed pterosaur yet identified.
Ctenochasma This pterosaur had over 200 needle-like teeth.
Cuspicephalus This pterosaur's name is Greek for "pointy head."
Cycnorhamphus This "swan beak" was a close cousin of Pterodactylus.
Dimorphodon This big-headed pterosaur had two distinct types of teeth.
Dorygnathus A typical pterosaur from western Europe.
Dsungaripterus A typical pterosaur of the early Cretaceous.
Eudimorphodon This pterosaur flew the skies of Europe well over 200 million years ago.
Europejara The first identified tapejarid pterosaur from Europe.
Feilongus This narrow-beaked pterosaur was recently discovered in China.
Germanodactylus This flying reptile was once thought to be a species of Pterodactylus.
Gnathosaurus This "jaw lizard" was discovered in 1833.
Hatzegopteryx Might this pterosaur have been bigger than Quetzalcoatlus?
Jeholopterus This fanged pterosaur looked like a flying vampire.
Kryptodrakon The earliest pterodactyloid pterosaur in the fossil record.
Liaoningopterus This Asian pterosaur was a close relative of Anhanguera.
Muzquizopteryx A small, short-crested relative of the much bigger Nyctosaurus.
Nemicolopterus This tiny pterosaur was discovered in China in early 2008.
Ningchengopterus Was this newly hatched pterosaur capable of flight?
Nurhachius This pterosaur was named after a Chinese emperor.
Nyctosaurus This pterosaur came equipped with its own mast and sail.
Ornithocheirus One of the largest pterosaurs of the Cretaceous period.
Peteinosaurus One of the earliest known pterosaurs.
Preondactylus The earliest pterosaur in the fossil record.
Pteranodon What folks usually are referring to when the say "pterodactyl."
Pterodactylus The first pterosaur ever to be discovered--and still the most famous.
Pterodaustro A weirdly beaked cousin of Pterodactylus.
Rhamphorhynchus This pterosaur's remains are unusually well preserved.
Quetzalcoatlus One of the largest creatures ever to take to the skies.
Scaphognathus A small, rhamphorhynchoid pterosaur of the late Jurassic period.
Sericipterus This "silk winged" pterosaur was recently discovered in China.
Sordes A pigeon-sized pterosaur of the late Jurassic.
Tapejara A colorful pterosaur from South America.
Thalassodromeus This South American pterosaur had a gigantic head crest.
Tropeognathus This "keel jaw" was a close cousin of Ornithocheirus.
Tupuxuara A colorful pterosaur closely (and confusingly) related to Tapejara.
Wukongopterus This pterosaur was a close relative of Darwinopterus.
Zhejiangopterus One of the best preserved of the giant pterosaurs.