Plants are tough to chew. Modern grass-eaters like cows and horses use giant flat teeth that wear down quickly. Hadrosaurs - the duck-billed dinosaurs of the Cretaceous - solved the problem with one of the most efficient chewing setups in animal history.
Instead of having a single layer of teeth, their jaws contained “dental batteries” - stacks of dozens of teeth packed together, each one ready to take the place of the one above it. As the top tooth wore down from chewing, a fresh one rose up to replace it. Some hadrosaurs had over a thousand teeth in their mouths at once.
That meant a hadrosaur could chew tough, woody, abrasive plants its entire life and never run out of teeth - a huge advantage over predators, which often broke their teeth and had to grow them back slowly one at a time.
