Add Yahoo as a preferred source to see more of our stories on Google. An artist's impression of Praearcturus gigas. (Franz Anthony) If you were wandering around Earth's floodplains 415 million years ...

If you were wandering around Earth's floodplains 415 million years ago, you wouldn't have come across any other mammals – but you would have had to be wary of a giant scorpion measuring more than a ...