Why do scientists think that the Iguanodon is a herbivore?

There are a number of clues that scientists look for to determine the diet of an animal. One is the shape of the teeth. In Iguanodon, the teeth aren't sharp or serrated, and are designed for chewing plants, not killing or dismembering animal prey. Another clue is the claws. If an animal has a lot of sharp claws, it is more likely to be carnivorous. With the exception of its thumb claws, Iguanodon didn't have sharp claws, and its thumb claw was probably used for self defense. Another hint is the jawbone. The jaw wasn't designed to bite down firmly on prey like the jaws of a carnivorous dinosaur such as Tyrannosaurus or Allosaurus.