Stygimoloch

Stygimoloch was a plant-eating dinosaur that had bony spikes and knobs on its skull. This bipedal dinosaur lived during the late Cretaceous period, about 68 million to 65 million years ago.
Like other pachycephalosaurids, Pachycephalosaurus was a bipedal herbivore with an extremely thick skull roof. It had long hindlimbs and small forelimbs. Pachycephalosaurs probably head-butted as a defense and in rivalry.
22% of all domes examined had lesions suggesting osteomyelitis. This is an infection of the bone resulting from trauma. So pachycephalosaurid domes were probably used in intra-species combat.
"Stygimoloch" fossils were first discovered in North America, in Montana and Wisconsin. The first was discovered in Hell Creek, Montana and was named in 1983 by Peter M. Galton, a British paleontologist and Hans-Dieter Sues, a German paleontologist.