Dinosaurs were one of several kinds of prehistoric reptiles that lived during the Mesozoic Era, also known as the “Age of Reptiles.” Even though we still don’t know or can’t be certain about many things concerning dinosaurs (for example, paleontologists can only speculate how they behaved, how they mated, what color they were, or even whether a fossil belonged to a male or female dinosaur), we know for a fact there were lots of different kinds of dinosaurs that lived at various times. Some walked on two legs (they were bipedal), some walked on four (they were quadrupedal), some could do both, some were armor-plated, some had horns, crests, or spikes, and they have been a source of inspiration for writers, directors, and storytellers for more than a century. The details of their extinction (among other details about them) remain a mystery and paleontologists are furiously studying their remains to learn about their prehistoric world. Take a revealing look into our prehistoric past with these 25 Giant Facts You Might Not Know About Dinosaurs.