Patagium
patagium [pəˈtājēəm] a membrane or fold of skin between the forelimbs and hind limbs on each side of a gliding mammal ========== OK, so flying squirrels don't really fly. They glide. In order to achieve this method of locomotion, flying squirrels have developed a unique adaptation called a patagium. The patagium is a furred membrane of skin, stretching from the fore leg to the hind leg. Underneath the skin of the patagium lay long thin muscle groups that control some of its movement, and along the edge lies a group of intertwined muscle that serves to hold the skin flaps in various degrees of tautness as required during its glide. When not gliding, yet another muscle group controls the now loose skin, keeping it out of the way when running, walking and sitting.  The patagium attaches to the fore leg via the styliform cartilage (see image at right), a rod-like appendage that allows the patagium to be extended further than would be the case without such a feature, thereby increasing the area of the leading edge, and the total area of the airfoil. When not gliding, the styliform cartilage rests unobtrusively parallel alongside the fore leg. The fur on the patagium is shorter than its body fur, in order to minimize air flow resistance or "aerodynamic drag". |