Flying squirrel

 Flying squirrels are not capable of powered flight like birds or bats; instead, they glide between trees. They are capable of obtaining lift within the course of these flights, with flights recorded to 90 meters (295 ft). The direction and speed of the animal in midair is varied by changing the positions of its two arms and legs, largely controlled by small cartilaginous wrist bones. This changes the tautness of the patagium, a furry parachute-like membrane that stretches from wrist to ankle. It has a fluffy tail that stabilizes in flight. The tail acts as an adjunct airfoil, working as an air brake before landing on a tree trunk.

The colugos, Petauridae, and Anomaluridae are gliding mammals, which are similar to flying squirrels, because of convergent evolution. A few mammals can glide through the trees, but they do not actually fly (like birds and bats). They have a membrane of skin on either side of their body.

The Siberian flying squirrel ranges from the Baltic Sea in the west to the Pacific Ocean in the east.

Prior to the 21st century, the evolutionary history of the flying squirrel was frequently debated. This debate was clarified greatly as a result of two recent molecular studies. These studies found support that flying squirrels originated 18–20 million years ago, are monophyletic, and have a sister relationship with tree squirrels. There are four hypotheses as to why gliding has evolved in mammals: economical locomotion, foraging optimization, evasion of predators, and control of landing forces.