It could bite a shark in two. It might have been the first "king of the beasts." And it could teach scientists a lot about humans, because it is in the sister group of all jawed vertebrates.

Dunkleosteus terrelli lived 400 million years ago, grew up to 33 feet long and weighed up to four tons. Scientist have known for years that it was a dominant predator, but new embargoed research to be published in the Royal Society journal Biology Letters on November 29 reveals that the force of this predator's bite was remarkably powerful: 11,000 pounds. The bladed dentition focused the bite force into a small area, the fang tip, at an incredible force of 80,000 pounds per square inch.

ore here (http://www.sciencedaily.com/releases/2006/11/061129094125.htm)