 With the advent of cladistic analyses , Iguanodontidae as traditionally construed was shown to be paraphyletic , and these animals are recognised to fall at different points in relation to hadrosaurs on a cladogram , instead of in a single distinct clade . Essentially , the modern concept of Iguanodontidae currently includes only Iguanodon . Groups like Iguanodontoidea are still used as unranked clades in the scientific literature , though many traditional iguanodontids are now included in the superfamily Hadrosauroidea . Iguanodon lies between Camptosaurus and Ouranosaurus in cladograms , and is probably descended from a camptosaur @-@ like animal . At one point , Jack Horner suggested , based mostly on skull features , that hadrosaurids actually formed two more distantly related groups , with Iguanodon on the line to the flat @-@ headed hadrosaurines , and Ouranosaurus on the line to the crested lambeosaurines , but his proposal has been rejected . 
