Giant pterosaurs, colossal winged reptiles that lived alongside the dinosaurs, have long been considered the heaviest animals ever to take to the skies. But new research suggests that the notion of giant pterosaurs soaring over Earth simply doesn't fly.Based on the weights and body sizes of modern birds, a new study finds that animals heavier than 90 pounds (41 kilograms) with wingspans greater than 16.7 feet (5.1 meters) wouldn't be able to flap fast enough to stay aloft. The conclusion casts serious doubt on the flying ability of large pterosaurs such as Quetzalcoatlus, thought to be one of the largest airborne animals of all time. [...]