Iguanodon anglicus

These teeth, found in southeast England in 1822, were a discovery of monumental significance. They were the first fossils to inspire the idea that giant reptiles (later named dinosaurs) used to walk the Earth. Mary Ann Mantell, the wife of the doctor and palaeontologist Gideon Mantell, discovered them by accident in a pile of gravel in Sussex. The fossils were later traced to a quarry containing Early Cretaceous rocks from 140 to 136 million years ago. Gideon Mantell spent three years refining his theory that giant reptiles once existed, finally naming the teeth Iguanodon and publishing his idea in 1825.