Caption:
An unsuspecting family of Pachycephalosaurus is being stalked by a T-Rex dinosaur.. . Better understanding of morph stages for certain dinosaurs has shown that what used to be Dracorex is actually a juvenile Pachycephalosaurus. Four growth stages have been identified and they illustrate the change in head bone from a young juvenile, juvenile, sub-adult to adult. The frills and horns or many ceratopsians undergo these transformations as well.