pachycephalosaur noun1 •Any of a group of herbivorous dinosaurs, of the genus Pachycephalosaurus from the late Cretaceous period.One could almost call Triopticus a mimic were it not for the fact that it dates to 228-220 million years ago, meaning that it predates the pachycephalosaurs by over 100 million years. — 2016 formspachycephalosaurs
