Long before the T-Rex or the Mosasaurus ruled the world, the oceans belonged to this guy. Meet the Dunkleosteus. It lived about 360 million years ago (in the Devonian Period), which means it is older than the very first dinosaurs. The "Teeth": If you look closely at its mouth, those aren't actually teeth. They are massive, self-sharpening sheets of bone that acted like a guillotine. The Bite: Scientists estimate their bite force was around 8,000 PSI. To put that in perspective, that is strong en