It’s the rut season for Pachycephalosaurus wyomingensis in Late Cretaceous North America around 66 million years ago, and one of the young rams is about to ram into his competitor’s flank in a duel to see who can win over the local ewes. It was once common to depict these dome-headed dinosaurs as butting heads like modern bighorn sheep, but ramming into each others’ sides seems at least as likely if not more so as I understand it.