In the Lower Cretaceous there were many pterodactyloids, mostly quite small. Gradually, larger versions evolved, and by the Upper Cretaceous most pterosaurs had huge wing-spans and clearly covered huge distances soaring on upcurrents in a warm environment. "Pteranodon", with a wing-span of over 20 feet (7m), and "Quetzalcoatlus", with a wingspan of 40 feet (12m) are famous examples. The question of their eating habits is still undecided.