Living: When it was time for the Pachycephalosaurs to find a mate, the males stuck their heads together to determine which one was lucky enough to get a female. The size of their skull depends of how old the dinosaur was.

By Shiraishi Mineo

It has been proved that it could hold its back and tail horizontal. That worked as a shock absorber when the males fought for their females. But a thick skull is not enough to handle a Theropod, so their defense-system consisted of noises and quick movements.

Skull: Its thick skull protected the little brain and its big nose-holes and eye-sockets indicate that it had a good olfactory sense and great vision.

Skullborder: The border on the side of the skull does not mean, that it is related to the Ornithopods, but the Psittacosaurids and Ceratopsids.