Triceratops
One skull, assigned to Triceratops, has a hole in the jugal bone. It looks like a puncture wound sustained while the animal was still alive.  This is supported by signs of healing that are present in the bone around the supposed wound. When examined closely, the hole in the bone has a diameter that is very similar to diameter of the distal end of a Triceratops horn. This is evidence of competition between individual dinosaurs.Martin A.J. 2006. Introduction to the study of dinosaurs. 2nd ed, Oxford, Blackwell. pg. 299-300. .