A bat is the only mammal that can fly. The wings of a bat are very different than the wings of a bird. Bat wings are modified arms. The bones in a bat's wing are like the bones in a human arm. A bat's wing has two thin layers of flexible skin stretched between their fingers. The thumb of a bat is like a claw. It is used to help a bat move across rough surfaces like cave walls.

Bat Skeleton See how similar our skeletons look. What do they have in common? What is different?	Human Skeleton
Observe the wings: point to the fingers.	Point to the thumb. Point to the shoulders.