Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, and Ouranosaurus. Iguanodonts were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and include the "duck-billed" hadrosaurs. Iguanodontians were fairly large animals, and some (such as Shantungosaurus, which measured up to 50 ft (15 m) in length and weighed up to 8 tons) approached the largest carnivorous dinosaurs in size.