The history of Iguanodon goes back almost 200 years. The first fossil remains of Iguanodon were collected in the 1820s from the gravels of Tilgate Forest in southern England. The fossils consisted of large teeth, similar is shape to those of a modern iguana, but much larger. These fossils were amongst the first dinosaur remains ever found. However, at that time nobody knew what a dinosaur was! So, these mysterious giant teeth shed the first light onto an ancient prehistoric world.
The teeth, along with some other isolated bones, were given the name Iguanodon in 1926. The name means ‘iguana tooth’. It was thought to be a giant reptile but, since this was before the word ‘dinosaur’ was even invented, the early paleontologists had a difficult task reconstructing Iguanodon from its fragmentary fossils. It was originally thought to be a lumbering four-legged monster, similar to an iguana, with a horn on its nose. Later discoveries of complete articulated skeletons led to it being regarded as a biped with a posture more like a kangaroo, and the horn on its nose was correctly identified as a thumb spike. Today, Iguanodon is thought to have walked on four legs most of the time – the early 19th century palaeontologists were right about that after all!
Fossil trackways of Iguanodon show that it was a social animal that lived in herds. This is because there is safety in numbers. It used its horny beak and leaf-shaped teeth to chomp through vegetation. Most of its claws are blunt and hoof-like, but a sharp spike on its thumb provided a defensive weapon to protect itself from predatory dinosaurs.
Iguanodon was the first plant-eating dinosaur to be named, early in the history of dinosaur palaeontology, and so dozens of later dinosaur species were also allocated to the genus Iguanodon. However, modern studies have shown that these former Iguanodon species are actually distinct dinosaurs. For example, one of the best known of these species (‘Iguanodon’ atherfieldensis) was given the new name Mantellisaurus in 2007. Today, there are only two valid species of Iguanodon: I. bernissartensis from northern Europe, and I. galvensis from Spain. Iguanodon occupied Europe during the Early Cretaceous, 125 million years ago, and is one of the best known of all dinosaurs.