There are 43 flying squirrel species in the world. The red and white giant flying squirrel (Petaurista alborufus) is the biggest. It's about 40 centimeters or feet long, I forget which. Burrard-Lucas Photography captured this great shot of one in the Qinling Mountains of China.
Link -via TYWKIWDBI | Photographer's Website
http://en.wikipedia.org/wiki/Varan_the_Unbelievable