December 20 , 2016:

Marginocephalia (Ornithischia: Cerapoda) is a clade of ornithischian dinosaurs that includes Ceratopsia and Pachycephalosauria. This clade is predominantly characterized by a prominent parietosquamosal shelf extending posteriorly over the occiput in the form of a large frill in ceratopsians and a thickened frontoparietal dome in pachycephalosaurs. The function of the respective parietosquamosal shelves has been the subject of much debate in paleontological discussions. Common hypotheses of parietosquamosal shelf function include defense structures in ceratopsians, “battering-rams” in pachycephalosaurids, and display structures for both clades. However, the high variability of ornamentation in both groups suggests similar variability in display functions and combative styles. To trace the potential functions of marginocephalians ornamentation, a collection of 62 pachycephalosaur frontoparietal domes and 45 ceratopsian skeletons from taxa throughout the marginocephalian phylogeny was surveyed for pathologies to assess the frequency and distribution of injuries. Preliminary results show a strong correlation between unique ornamentation morphologies and distributions of frequent injuries. These results suggest that a suit of combative behaviors exists in marginocephalians, comparable to those observed in extant bovids with highly variable cranial horns and ornamentation, as well as likely serving as effective sexual selection structures.

Joseph E. Peterson (2015)
Evolution of marginocephalian combat and patterns of pathology distribution.
68th Annual Field Conference Guidebook: Cretaceous Conference: Evolution and Revolution
2013 Wyoming Geological Association Guidebook: 141-149