Over the years, everybody's favorite dinosaur, Tyrannosaurus Rex, has changed radically. When I was a kid, dinosaurs were slow, lumbering, stupid, cold blooded animals. They were primitive and had small brains. They walked sort of upright, dragging their tails.  

Just looking at the pictures of T-Rex and you could tell it was a dumb animal. Then paleontologists began to question those assumptions. First there was questions about the evidence that the dinosaurs were cold blooded. Led by Robert Bakker, paleontologists started seeing the the same evidence – the same bones – in a new way. T-Rex stopped dragging his tail and started looking more alert and dangerous.

Then came DNA testing and we learned that dinosaurs were related to birds. So we now have the new T-Rex. Complete with proto-feathers. T-Rex has never been an animal anybody would want to mess with, but this latest version looks particularly bad-ass.