Scientists have found new evidence for how armored dinosaurs used their iconic tail clubs. The exceptional fossil of the ankylosaur Zuul crurivastator has spikes along its flanks that were broken and re-healed while the dinosaur was alive — injuries that the scientists think were caused from a strike by another Zuul’s massive tail club. This suggests ankylosaurs had complex behavior, possibly battling for social and territorial dominance or even engaging in a ‘rutting’ season for mates.