In 1825, Iguanodon became only the second dinosaur to be scientifically described. It was named for its iguana-like teeth, which also provided the first indication that dinosaurs were reptiles.

As one of the few dinosaurs capable of walking on either two feet or four, it could browse on low-lying plants and also rear up on its hind legs to reach higher vegetation. Iguanodon fossils have been found in groups, suggesting that they may have lived in herds.