Iguanodon ("Iguana Tooth") was an ornithopod dinosaur from the Cretaceous period which lived during the Early to Late Cretaceous.
Iguanodon lived during the Early to Late Cretaceous period from 145-65 million years ago. They were very successful dinosaurs that had been around for 80 million years and they colonized every single continent. They were prey aimals for carnivores like Sarcosuchus, Utahraptor, and the immense Giganotosaurus.
There were several species of Iguanodon all across the globe during the Cretaceous period and they varied in size and appearances. They all weighed about 3-4 tons, but the North American species, named Dakotadon lakotaensis, was the smallest and measured about 30 feet long and stood 10 feet tall at the hips. The larger European species, called Iguanodon bernissartensis, was 33 feet long and 11 feet tall at the hips. The largest was a South American species known as Macrogryphosaurus gondwanicus, measuring 36 feet long and standing 12 feet tall at the hips.
Although these herbivores walked on four legs, Iguanodon could run on just two. And this makes them quit nimble, more so than slow-moving dinosaurs like the ankylosaurus, such as Polacanthus.
Like many herbivores, Iguanodon lived in columns of huge herds, as many hundreds of thousand tons of individual dinosaurs in herds. The young often played around the adults.
Iguanodon were very successful dinosaurs, in fact, among the most successful dinosaurs on Earth, inhabiting all the worlds continents and prospering in various plants and vegetation. One particular reason Iguanodon were as successful as they were was because they developed a new way of dealing with plants in the Cretaceous. Most dinosaurs, carnivore or herbivore, could only crudely slice food with their teeth. Iguanodon, however, were not only the first herbivores, but the first dinosaurs, to have back teeth that could grind up vegetation before swallowing. This ability to chew sped up the digestion of even the toughest planet material.