 Exactly what Iguanodon ate with its well @-@ developed jaws is not known . The size of the larger species , such as I. bernissartensis , would have allowed them access to food from ground level to tree foliage at 4 – 5 metres ( 13 – 16 ft ) high . A diet of horsetails , cycads , and conifers was suggested by David Norman , although iguanodonts in general have been tied to the advance of angiosperm plants in the Cretaceous due to the dinosaurs ' inferred low browsing habits . Angiosperm growth , according to this hypothesis , would have been encouraged by iguanodont feeding because gymnosperms would be removed , allowing more space for the weed @-@ like early angiosperms to grow . The evidence is not conclusive , though . Whatever its exact diet , due to its size and abundance , Iguanodon is regarded as a dominant medium to large herbivore for its ecological communities . In England , this included the small predator Aristosuchus , larger predators Eotyrannus , Baryonyx , and Neovenator , low @-@ feeding herbivores Hypsilophodon and Valdosaurus , fellow " iguanodontid " Mantellisaurus , the armoured herbivore Polacanthus , and sauropods like Pelorosaurus . 
