Prehistoric animals once roamed — and ruled — planet Earth. Some of them, like the giant sloth or the woolly rhino, were generally gentle. Others, like the saber-toothed tiger and the dire ...

Some were the size of a dog. Others were as large as polar bears. A newly-discovered fossil of the ferocious hyaenodont is ...

Polar bears are one of the largest surviving prehistoric animals. Their existence is deeply connected to the health of polar ecosystems.