Many vertebrates have independently evolved the ability to glide. In spite of their name, "flying" squirrels (Glaucomys volans and Glaucomys sabrinus) glide, not fly, from tree to tree. The little marsupial known as a sugar glider (Petaurus breviceps) can also glide from tree to tree. Many other animals practice parachuting. The difference between parachuting and gliding is control. Parachuting is simply slowing the rate of descent with little or no attempt to control direction. Flying squirrels carefully steer themselves as they glide from the crown of one tree to the trunk of another.

Cynocephalus is a group of medium-sized gliding mammals closely related to bats. These mammals hang upside down in trees, leaping into the air to glide in search of fruit to eat. The group Exocoetus contains the "flying" fishes. Although a true glider, Exocoetus can extend the range of its glide by...