 Tyrannosaurid skulls had many unique characteristics , including fused parietal bones with a prominent sagittal crest , which ran longitudinally along the sagittal suture and separated the two supratemporal fenestrae on the skull roof . Behind these fenestrae , tyrannosaurids had a characteristically tall nuchal crest , which also arose from the parietals but ran along a transverse plane rather than longitudinally . The nuchal crest was especially well @-@ developed in Tyrannosaurus , Tarbosaurus and Alioramus . Albertosaurus , Daspletosaurus and Gorgosaurus had tall crests in front of the eyes on the lacrimal bones , while Tarbosaurus and Tyrannosaurus had extremely thickened postorbital bones forming crescent @-@ shaped crests behind the eyes . Alioramus had a row of six bony crests on top of its snout , arising from the nasal bones ; lower crests have been reported on some specimens of Daspletosaurus and Tarbosaurus , as well as the more basal tyrannosauroid Appalachiosaurus . 
