Timeline of pachycephalosaur research

One of the first major events related to the history of pachycephalosaur research actually regards the discovery of an unrelated dinosaur called Troodon, reported from the western United States by Joseph Leidy in 1856.

The idea that it was used in head butting between members of the same pachycephalosaur species was first proposed by science fiction writer Sprague de Camp.

[4] Nevertheless, this perennial hypothesis would come to be criticized by researchers like Hans-Dieter Sues as less likely than "flank butting" where pachycephalosaurs' domed heads would be aimed at rivals' bodies rather than in head-to-head combat.

Others, like Goodwin and others have thought the dome purely for display because its high density of internal blood vasculature may have rendered it too fragile for combat.

[4] Meanwhile, in 1998 Chapman and others found the biomechanics of pachycephalosaur domes consistent with the old head-butting hypothesis, suggesting that the idea retains scientific merit.