Iguanodon ( / ᵻˈɡwɑːnədɒn / i @-@ GWAH @-@ nə @-@ don ; meaning " iguana @-@ tooth " ) is a genus of ornithopod dinosaur that existed roughly halfway between the first of the swift bipedal hypsilophodontids of the mid @-@ Jurassic and the duck @-@ billed dinosaurs of the late Cretaceous . While many species have been classified in the genus Iguanodon , dating from the late Jurassic Period to the late Cretaceous Period of Asia , Europe , and North America , research in the first decade of the 21st century suggest that there is only one well @-@ substantiated species : I. bernissartensis , which lived from the late Barremian to the earliest Aptian ages ( Early Cretaceous ) in Belgium and possibly elsewhere in Europe , between about 126 and 125 million years ago . Iguanodon was large , bulky herbivores . Distinctive features include large thumb spikes , which was possibly used for defense against predators , combined with long prehensile fifth fingers able to forage for food .