I don't know about the sexual combat usage idea...I wonder if paleontologists often say "well, we don't know what this thing is for... it myst have been for sexual display!!!" Sadly, there is no way to prove or disprove a suggestion like this one-sex behaviors don't fossilize too well. We'll just have to wait for a discovery of a Mesozoic playboy(saur)... Ethan Skinner