Archelon was a huge turtle that lived in the late Cretaceous sea, roughly 75-65 million years ago. It was 15 feet long and had a very powerful beak, which chould have snapped a divers leg in two if one annoyed it. Scientists studying Archelon during the Cretaceous would have had to stay on its back to be out of the way of its beak, although several creatures did prey on the Archelon. Because of its size, Archelon does not have a shell made of the same substance as contemporary shells, instead it has a carapace of thin bone stretched across its back, otherwise it would be far too heavy. It did not have any exact or known predators but any predator may have attacked it, such as a Mosasaur.