 Bony crests are found on the skulls of many theropods , including many tyrannosaurids . Alioramus , a possible tyrannosaurid from Mongolia , bears a single row of five prominent bony bumps on the nasal bones ; a similar row of much lower bumps is present on the skull of Appalachiosaurus , as well as some specimens of Daspletosaurus , Albertosaurus , and Tarbosaurus . In Albertosaurus , Gorgosaurus and Daspletosaurus , there is a prominent horn in front of each eye on the lacrimal bone . The lacrimal horn is absent in Tarbosaurus and Tyrannosaurus , which instead have a crescent @-@ shaped crest behind each eye on the postorbital bone . These head crests may have been used for display , perhaps for species recognition or courtship behavior . 
