Pachycephalosaurus is believed to have grown to be about 15 feet long and probably weighed in excess of 900 pounds. This dinosaur is known for its five-fingered claws, long powerful legs, and three-toed clawed feet. However, it is most known for its thick domed skull. This dinosaur’s skull wall could be as much as ten inches thick. This thick skull plate was also surrounded by bony knobs. Paleontologists believe that this skull plate was used by the dinosaurs either as a self-defense mechanism or to butt heads with other Pachycephalosaurus dinosaurs, kind of like what big horned sheep do. However, some paleontologists believe that this couldn’t have been the case. They posit that these dinosaur’s skulls were not heavy enough to absorb such impacts and that there haven’t been any fossil specimens of this dinosaur that have been found with the skull damage that would likely happen during such impacts.