There's a lot of debates in paleontology. Is T. rex a scavenger? Are Triceratops and Torosaurus the same? Though the former is pretty famous to laymen and normal people, the particular debate we're talking about is one generally more known among people in the paleontology field. The debate is: did pachycephalosaurs butt heads? Well, a recent discovery might have the answer. Described as "it looked like someone went through it with a hammer", an injury in the skull dome of a Pachycephalosaurus shows that they most likely did, indeed, butt heads (you can hear your little siblings laughing at this already).