Patagium

The patagium is a membranous structure that assists an animal in gliding or flight. The structure is found in bats, birds, some dromaeosaurs, pterosaurs, and gliding mammals.

Bats

In bats, the skin forming the surface of the wing is an extension of the skin of the abdomen that runs to the tip of each digit, uniting the forelimb with the body.

The patagium of a bat has four distinct parts:

Pterosaurs

In the flying pterosaurs, the patagium is also composed of the skin forming the surface of the wing. In these ornithodirans, the skin was extended to the tip of the elongated fourth finger of each hand.

The patagium of a pterosaur had three distinct parts: