Pterosaur

Pterosaurs were an extinct clade of flying reptiles. They lived during most of the Mesozoic era. This period lasted from 228 million to 66 million years ago. Pterosaurs were the first vertebrates to evolve powered flight. This means they could flap their wings to fly. They are not actually dinosaurs. Dinosaurs and pterosaurs belong to different groups. However, pterosaurs are more closely related to birds than to crocodiles.

To fly, pterosaurs needed very light but strong bodies. Their bones were hollow and filled with air. This made their skeletons much lighter for flight. The bone walls were often as thin as paper. They also had a large, keeled breastbone. This bone provided a place for strong flight muscles to attach. To stay stable, some later species had a notarium. This was a structure where several vertebrae fused together. It helped stiffen the torso during flight.

Their wings were highly complex structures. The wing was a membrane made of skin, muscle, and tissue. This membrane stretched from the ankles to a very long fourth finger. The wing was divided into three main parts. The propatagium was the forward-most membrane. The brachiopatagium stretched from the finger to the hindlimb. Finally, the uropatagium or cruropatagium stretched between the legs.

To keep the wing from flapping loosely, they had actinofibrils. These were closely spaced fibers arranged in three crisscross layers. These fibers helped the animal adjust the shape of its wing to control lift.

Pterosaurs are often divided into two major types. The first type is the basal pterosaurs. These were often smaller animals with wingspans up to two meters. They usually had long tails and teeth in their jaws. They also had wide wing membranes that connected to their hindlimbs. The second type is the pterodactyloids. These evolved later and had many different shapes. They had much shorter tails and longer necks. They also had long metacarpals, which are the bones in the hand. This allowed them to walk upright on all four limbs.

These animals were very active and warm-blooded. Scientists call this being endothermic. To support this active lifestyle, they had a special respiratory system. They used air sacs to create unidirectional breathing. This means air flowed through their bodies in one direction. This system provided a constant supply of oxygen to their muscles. They also had hair-like filaments called pycnofibers. These covered their bodies and parts of their wings. These filaments may have worked like down feathers to provide insulation.

Pterosaurs came in many different sizes. Some species, like the anurognathids, were very small. Others were the largest flying creatures in Earth's history. The Azhdarchidae family included massive giants. One example is Quetzalcoatlus, which had a wingspan of at least nine meters. Another giant was Hatzegopteryx. These massive animals were much larger than any bird alive today.

The skulls of pterosaurs were also very diverse. Many species had large holes in their skulls for breathing and seeing. Some had long, narrow snouts. Others had large, bony crests on top of their heads. These crests could be very large and were sometimes made of soft tissue. Some pterosaurs had teeth to eat fish or insects. Other groups evolved horny beaks, similar to modern birds. This variety shows how many different ways they lived and ate.