Iguanadon

Iguanadon was a bulky ornithopod, the first dinosaur to be discovered (1822) and the second to be officially named (after megalosaurus). Due to the initial discovery being of it's teeth, and the fact it was one of the first dinosaurs to be discovered, it's name was derived due to the similarity between the find and modern day iguana teeth.

Originally thought to stand like a kangaroo, it is now believed that iguanadon would have spent the majority of it's time on four legs, perhaps rearing up to grab high vegetation. It's robust arms and fused wrist bones provide evidence for this theory.

A notable feature of iguanadon was a sharp thumb spike on each hand. This may have been used as a defensive weapon or perhaps to assist when foraging for food.