 Tyrannosaurids , like their tyrannosauroid ancestors , were heterodont , with premaxillary teeth D @-@ shaped in cross section and smaller than the rest . Unlike earlier tyrannosauroids and most other theropods , the maxillary and mandibular teeth of mature tyrannosaurids are not blade @-@ like but extremely thickened and often circular in cross @-@ section . Tooth counts tend to be consistent within species , and larger species tend to have lower tooth counts than smaller ones . For example , Alioramus had 76 to 78 teeth in its jaws , while Tyrannosaurus had between 54 and 60 . 
