It's popular science to claim birds are dinosaurs, but it has nothing to do with this creature. These are giant flying reptiles. How did these giant reptiles ever get off the ground? Also, there are claims people have seen them, so questions remain if they are extinct. "The 'dinosaur' popularly known as a pterodactyl is actually called a reptile called a pterosaur, which is Greek for flying lizard. It existed alongside the dinosaurs between 251 and 65 million years ago, and were thought to be the biggest creatures to ever take to the air. The fossilised remains of one example had a wing span of more than 15 metres. But Katsufumi Sato, a Japanese scientist, who collected data from five large birds including the world's biggest, the wandering albatross, has calculated that it was physically impossible for them to stay aloft. The University of Tokyo professor claims that the largest animal capable of soaring across the sky unaided could have weighed no more than 40kg (88lbs) or the size of a labrador dog. Prof Soto, who reported his findings in New Scientist magazine, travelled to the Crozet Islands - halfway between Madagascar and Antarctica - and attached accelerometers, devices the size of AA batteries which measure thrust, to the wings of 28 birds from the five species including the albatross which is a soarer like the pterosaurs were thought to be. Unlike turkeys or bustards, whose short wings are good for quick take-off but not for soaring, these larger birds fly long distances using dynamic soaring - they ride changing wind currents without moving their wings. But when the wind dies down, or blows at a constant speed, they have to flap or be pulled down by air resistance and gravity. The maximum speed a bird can flap is limited by its muscle strength and decreases for heavier species with longer wings. Prof Sato says animals heavier than 40kg would not be able to flap fast enough to stay aloft. This would explain why the wandering albatross weighs only 22 kg (46lbs). A bird weighing too close to 40kg would be incredible unstable and "would not have a safety margin to fly in bad weather", he added." Pterodactyls were too heavy to fly, scientist claims Pop science article Pterodactyl, Pteranodon & Other Flying 'Dinosaurs'