Largest pachycephalosaur dinosaur

Pachycephalosaurs were bipedal dinosaurs famous for their exceptionally thick skulls, which they would use as battering rams against one another, rather like head-butting rams do today. The largest pachycephalosaur was Pachycephalosaurus wyomingensis, which is estimated from fossil evidence to have measured up to 7 m long and was therefore more than twice the length of any other known pachycephalosaur. It lived up to the end of the Cretaceous Period, 65 million years ago, in what is today the state of Wyoming and elsewhere in the USA.