If you've seen Jurassic Park, you might be familiar with the Stegosaurus. Most kids know it by the double-row of bony plates it had on its back, but new evidence shows its main weapon was actually its tail. Frank Sanders and his colleagues at the Denver Museum of Natural History did a study where they were examining the meter-long spikes that came out of a stegosaur's tail.
The three-foot spikes seem to be made of the same stuff as horns and claws. And while a tail may seem like a pretty unwieldy weapon, when it bonked you, it bonked you with more than a thousand times the air pressure, all concentrated in one spot.
Sanders has also discovered the tail bone of an allosaur with a hole in it the size of a silver dollar. Allosaurs are meat-eating dinosaur that might have tried to make a snack out of stegosauri. Sanders says the force of the stegosaur tail would have been enough to punch through hide and even bone, and could very well be the source of the hole in the allosaur tail.