Did you know that dinosaurs weren't the only prehistoric beasts on Earth? Even before the time when dinosaurs lived, there were many other incredible creatures, and some were even bigger and more terrifying than T. rex. Entelodonts had strong jaws designed to crush bones. Quetzalcoatlus was the largest ever flying creature—about the size of a fighter jet! And Dimetrodons were the first animals to have notched teeth for slicing through flesh. What would happen if these beasts came back to life? Imagine these prehistoric predators facing off against tigers, bears, and wolves—and learn all about the terrifying creatures of the past!