Four winged dinosaurs point to new ideas on flight

A surprising discovery of six dinosaur specimens in Laioning, China, shows evidence of feathery wings on both the fore and aft limbs of the animal, and reawakens the idea that birds might have come from dinosaurs gliding from tree to tree. The new discovery opens up a whole, unknown chapter in the development of flight, and may perhaps point to an intermediary stage between no-winged climbers and two-winged flappers.