Pterodactyls are flying reptiles that lived alongside the dinosaurs, between 220 and 65 million years ago. Although pterodactyls are not dinosaurs, the two groups are closely related. Pterodactyls were the first vertebrates to develop the power of flight, long before birds or bats took to the skies. Unlike bats or birds, pterodactyls flew on a web of skin stretched between a greatly elongated fourth finger and the torso. In fact, the name pterodactyl means "wing finger." Its wing spread was over 20 feet.