The Pachycephalosaurus had a reinforced skull, which was probably used when rival males fought each other.
Pachycephalosaurus was a medium-sized dinosaur, up to about 8 m long, although many of its relatives were much smaller. They all had an enormously thickened domed skull, and their spine was strengthened. Scientists think that adult males could ram each other with force when competing for a mate.
Despite its fierce appearance, Pachycephalosaurus was a plant-eater. In many forms, the skull was decorated with spikes and knobs of bone.
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