What is known about the pterosaurs:

* The fossilized remains of pterosaurs have been found on every continent except Antarctica

* Ranged in size from that of a sparrow to that of Quetzalcoatlus northropi, with its 40-foot wing span

* Make up an order of reptiles, the Pterosauria, arranged in two suborders -- the Rhamphorynchoidea and the Pterodactyloidea

* Only reptiles capable of powered (or "true") flight

* Had hollow bones with a very, very thin wall -- about 1/8-millimeter thick

* The wing of a pterosaur, a bird and a bat are evolutionary variations on a forelimb that was suitable for an earthbound animal that walked on all fours.

* Did not evolve into bird

* Over 50 percent of the wing membrane is supported by the wing finger (the fourth) which extends for about 60 inches

* The first pterosaur fossils were found in a limestone quarry near the Bavarian village of Eichsta tt and reported in 1784 by Cosimo Collini, a former secretary to Voltaire.

...And Don't

And what is still being debated?

* Were they fisheaters? Or did they use their long, piercing beak to catch frogs, salamanders, mollusks and arthropods?

* How did they reproduce: were they oviparous (or egg laying) or viviporous (giving birth to live young)?

* Were they bipedal, walking on two feet, as one pterosaur expert claims?

* How did they fly? Did they wait for the air currents to warm up, then ride the thermals? And to take off: did they spread their wings, take a few hops, a few flaps and off they soared?

* What was their world environment? Was it one of universal calm, with little seasonality or alternation between hot and cold?

* What caused them to die out? No one knows for sure but one theory is that a change toward greater seasonality created a stormy environment with gusting winds in which they couldn't fly.