Muskoxen (Ovibos moschatus) and bighorn sheep (Ovis canadensis) are known for their dramatic head-to-head battles. But all that noggin-knocking has a cost, researchers from the Icahn School of ...

Some scientists have postulated that Pachycephalosaurus's padded skull allowed these animals to engage in head-butting battles of dominance perhaps related to mating, much like bighorn sheep and ...