I love watching flying squirrels (Glaucomys sabrinus) on a warm summer night.
They really should be called gliding squirrels, because what allows them to be airborne is a loose flap of skin called the PATAGIUM.
When I think of it, bats also have a patagium. I love watching them on a warm summer night, too.
Dictionary.com also includes some reptiles and insects in this definition.