The evolution of ‘bizarre structures’ in dinosaurs: biomechanics, sexual selection, social selection or species recognition?

‘Bizarre structures’ in dinosaurs have four main traditional explanations: mechanical function, sexual selection, social selection and species recognition. Any of these can be plausible for individual species, but they fail to be persuasive when other lines of evidence cannot adequately test them. The first three also fail as general propositions when phylogenetic analyses based on other characters do not support scenarios of selective...