Sabertooth cats and other super-toothy predators apparently possessed mighty arms that they used to help them kill. The beefy arms would have served to pin down prey and protect the ferocious-looking teeth of the feline predators, which were actually fragile enough to fracture, scientists find. The finding also may hold for other knife-fanged prehistoric carnivores; long before sabertooth cats evolved, a number of now-extinct toothy hunters once roamed the Earth. These included the nimravids, or false sabertooth cats, which lived from 7 million to 42 million years ago alongside a sister group to cats known as barbourofelids, which lived from...