If you're scared of snakes then you certainly wouldn't be a big fan of the Titanoboa -the largest snake in history. This creepy critter stretched out 40 feet in length and weighed up to 2,500 pounds. The Titanoboa appeared right as the dinosaurs started to disappear, which left it a great niche to fill as a top predator. I've heard rumors of man-eating snakes, but all of those have proven to be fictional -on the other hand, this guy could easily munch down on a man.
Read about other terrifying prehistoric creatures over at All That Is Interesting