Born to Chew
Duckbilled dinosaurs had jaws made for grinding and crushing plants, just as cows and horses do today. Shantungosaurus, like other hadrosaurs, had rows of diamond-shaped overlapping teeth that allowed it to crush tough vegetation. A duckbilled dinosaur did not chew by moving its jaws from side to side like a cow. Instead, when it closed its jaws, the lower jaw forced both sides of the upper jaw outward, grinding the rows of teeth against each other and crushing whatever material was in the hadrosaur's mouth.
Replaceable teethHere you can see the rows of overlapping teeth. Hadrosaurs had hundreds of teeth in their mouths. When one tooth dulled or fell out, the dinosaur would simply grow a new one in its place.