Image: Jaw movement comparison: dinosaur and human
Iguanodon, Centrosaurus, Probactrosaurus and Edmontosaurus (and other hadrosaurs) chewed plants with their grinding back teeth. They probably had cheeks to prevent food from falling out during chewing. These dinosaurs didn’t chew like us and other mammals (the only living animals that can chew) because they had a different jaw structure. Their side-to-side chewing motion resulted from an expansion of the upper jaw when the mouth closed. Most mammalian plant-eaters chew with a sideways movement of the lower jaw.
- © Australian Museum