We now know what the missing teeth would have looked like at the front of this jaw. Eden, Janine and Jim/CC BY 2.0Until this week, Pachycephalosaurus seemed like a friendly neighborhood herbivore. The scariest thing about these dinosaurs, which have been frequently depicted placidly munching on greenery, was the unique architecture of their skulls: domed, sloping, pointy around the edges, and 10 inches thick. They might have butted heads, but that didn’t make them seem dangerous, exactly.But now, new research presented at a Society of Vertebrate Paleontology conference in Albuquerque, New Mexico, raises the specter that Pachycephalosaurus was a...