The Iguanodon was one of the first dinosaurs to be discovered and also the first named dinosaur creatures ever. With this scientists didn't know what to think. Strange enough to them, most lizards are carnivores but this one had cow like teeth making it obviously a herbivore. Not only that but the teeth were almost identical to what today's iguana teeth look like so they decided Iguanodon seemed to fit the name for this dinosaur. Still they've never seen anything so big before.
A full grown Iguanodon is 30 feet in length. The biggest land animal today is the African Bush Elephant which is 19.7 feet in length. That's got to be a little freaky to find out. Its no doubt they were that. There were a handful of complete skeletons found by numerous people in areas of Northern Europe, England, North America, Russia, Mexico, etc .like it was a monster or something
One of the most unique features of the Iguanodon had a big horny spike as thumbs. Chances are this was a defense mechanism from predators that the of the Early Cretaceous period like the Inventor. Some scientists argue thinking it could've been used for climbing but that's unlikely because of the size of the creature.