10 Prehistoric Creatures That Would Give You Nightmares If They Weren't Extinct

As goofy as it might sound, this was ultimately a deadly sloth. It seems difficult to believe that the modern adorable creatures have this hiding somewhere in their evolutionary history, but it's true. And they only died off around 10,000 years ago...it's very possible a few cave people had to deal with these monsters. 

The photo of that tooth really should sum this up pretty nicely. The Megalodon was supposedly around 60 feet long, and weighed between 50 and 100 tons. A Great White shark is usually about 20 feet long, so...take whatever you might feel watching Jaws, and multiply that by 3. 

This guy is 260 million years old, making it older than the dinosaurs. The Gorgonops was incredibly fast, large and had outrageously large teeth. 

This creature was 20 feet long and twice as mean. Just look at that jaw...you don't even want to be near that thing. 

Recognize this one? This is the distant ancestor of the crocodile. 40 feet long and weighing in at 8 tons, you didn't want to run into this creature on your family vacation to Florida. 

If you have earned the historic nickname of "Terror Bird," you were definitely up to no good. 

The Cretaceous period had to deal with this horrific beast, which was sort of like a crocodile but also with freaking FINS so it was outrageously fast in the water. Sounds like something from a nightmare, right? 

This ABSOLUTELY TERRIFYING creature went extinct around 2.5 million years ago, and good freaking riddance. It weighed 2,500 pounds and was the largest snake to ever exist. Indiana Jones would have a field day with this thing... 

28-Feet of pure terrifying predator. That jaw devoured many an opponent. 

This monster bird is thought to be the largest flying mammal to have ever existed on Earth, with a wingspan reaching the grand total of 35 feet and an estimated weight of about 500 pounds...YIKES.