Micropachycephalosaurus has the longest name of any dinosaur. It's 23 letters long. Ironically, it's one of the smallest dinosaurs as well. Adults have an estimated size of just over 3 feet in length and would have weighed less than 10 pounds. This tiny bone-head would have had few defenses due to it's small size. The best way for Micropachycephalosaurus to defend itself would be to run. Micropachycephalosaurus lived in Asia roughly 70 million years ago.