Pterosaur

**Pterosaurs** were flying reptiles which lived in the Mesozoic era at the same time as the dinosaurs. 

Many pterosaurs were fairly small, but in the Upper Cretaceous some grew larger than any other flying animals. The pterosaur *Quetzalcoatlus* had a wing-span of up to 12 metres (~40 feet).

The first fossils occur in the Upper Triassic, and the group continued until the K/T extinction event at the end of the Cretaceous (220 to 65.5 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were made from a flap of skin between their bodies and a big fourth finger (sometimes called the "wing finger"). The pterosaurs evolved into two groups. The earlier Rhamphorhynchoids (e.g. *Rhamphorhynchus*) had long tails and toothed jaws; The pterodactyloids (e.g. *Pterodactylus*) had short tails, and many had beaks with no teeth.

The first pterosaur fossil was discovered in the Late Jurassic Solnhofen limestone in Germany in 1784. This was exactly the same place as *Archaeopteryx* was found years later. Georges Cuvier first suggested that pterosaurs were flying creatures in 1801. Since the first pterosaur fossil was found, twenty-nine species of pterosaurs have been found in those deposits alone. 

A famous early UK find was an example of *Dimorphodon* by Mary Anning, in 1828 at Lyme Regis, Dorset, England. The name Pterosauria was coined in 1834.

Pterosaurs were genuine fliers, able to flap or soar. Their bodies were covered with fine hairs, so they were able to regulate their temperature (they were warm-blooded). They are a close sister-group to the dinosaurs, part of the Archosauria.

## Rhamphorhynchoids 
This early group did well from the Upper Triassic to the Lower Cretaceous. When we first see them in the fossil record they have split into three families, so biologists know their early evolution is not yet revealed.

To understand this, it helps to know some basic things about flight aerodynamics and stability. Early planes were highly stable, and so are airliners. To dart about quickly requires special advanced brains and reflexes, which later birds and pterosaurs had, but early ones did not. The analogy in planes would be fighter planes, which need such fast reactions that the details are worked out by computer, with the pilot indicating where to go. It requires more brains to control unstable flight than it does stable flight.

All species in the group have teeth. This again has a parallel with birds; *Archaeopteryx* and many Cretaceous birds have teeth; modern birds do not. The disadvantage of teeth is that they are quite heavy; when the animal can do without them, they will gradually get selected out. Obviously, without teeth food cannot be chewed, but there are ways around that. Stones in the gizzard do the grinding in birds.

For a long time it was thought that these pterosaurs died out at the end of the Jurassic, which was a minor extinction event. Even near the end of the Jurassic, *Rhamphorhynchus* was the most common pterosaur found at the famous *Archaeopteryx* site at Solnhofen in Bavaria, Germany. Now it is known that the group survived until the Lower Cretaceous. "Until recently, it was thought that rhamphorhynchoids died out at the end of the Jurassic, but new finds in the Jehol sequence of northeast China [show] that in this part of the world they survived until at least the middle of the Lower Cretaceous". The forests would have had many insects.

Since birds were already common in the Lower Cretaceous, they would have competed vigorously with the smaller pterodactyloids. That may explain the extinction of the smaller pterosaur species, though the lack of fossils from the forested areas makes it difficult to judge. The huge Upper Cretaceous type pterosaurs clearly lived a different life-style from the smaller species, and one which was not yet accessible to birds. As the climate changed in the Upper Cretaceous, becoming colder and more seasonal, the number of pterosaurs became fewer. Recent publications have shown that more pterosaurs survived to the end-Cretaceous event than was previously thought.

Like most of the larger species on Earth, the huge pterosaurs did not survive the K/T extinction event. At least some families of birds did. So ended the competition between the two types of flying reptile through the long 79 million years of the Cretaceous period. and Tilly Edinger showed that by the end of the Jurassic, pterosaur brains were more like that of modern birds than of *Archaeopteryx*. Recent work has used working model to simulate their flight.p218 The wing membrane was about 1mm thick, with a tough skin and had long fibres reinforcing it. This can be clearly seen in some of the fossils.p332 The structure helped the wings survive the stresses of flight. The larger pterosaurs were mainly soarers, as is the case with birds today.

How pterosaurs moved on the ground has been something of a mystery. It is most likely that they walked on four legs while on the ground, perhaps awkwardly.  Fossil tracks have been found showing they used both their legs and hands to support themselves.p210–222
 
Pterosaurs also had special bones. They were  light (even more than bird's wings – some were almost as thin as a piece of paper), and some were almost hollow. Tiny holes in the bones are evidence of air sacs which extended into the vertebrae and limb bones, as it does with birds. Also present were  struts which made these bones stronger. With these special bones, even the largest of pterosaurs, *Quetzalcoatlus*, probably weighed less than 200 pounds.

### Reproduction and development 
Pterosaurs were probably egg-layers, and some eggs have been found at pterosaur sites. There is evidence that some species, such as *Pteranodon*, had sexual dimorphism (sexes looked different). The skeletons with large cranial (head) crests and small pelvic canals were presumably males. Where several specimens occur at the same location, adults can be distinguished from juveniles. Evidence of tooth wear in *Eudimorphodon* suggests the young were insectivorous, while the adults ate fish.p343 Development took place rapidly in these warm-blooded reptiles, and much of their life-style parallels that of birds. The high energy-level needed for flight explains why both reptilian forms (pterosaurs and birds) developed similar metabolism. In many respects, birds and pterosaurs are good examples of convergent evolution.

## Related pages
* List of pterosaurs

## References
## Further reading
*Unwin, David M. 2006. *The pterosaurs: from deep time*. Pi Press, N.Y. ISBN  0131-46308-X
*Witton, Mark 2013. *Pterosaurs: natural history, evolution, anatomy*. Princeton University Press. ISBN 978-0691150611