In 1802, Jean Baptiste Lamarck explained that a fossil is a living organism turned into stone after spending many years in soil or water. In the 1800's, Georges Cuvier was very good at piecing together entire skeletons from only a few fossils, and he believed fossils were traces of a world now extinct. Gideon Mantell, while hunting for fossils in Britain in 1824, unearthed a partial femur the size of the biggest elephant bone. He sent it to William Buckland who knew how to reconstruct skeletons and determined it was from a very big lizard, which he called the Megalosaurus. Mantel found several new fossils from a very large herbivore reptile, which he called the Iguanodon. He then found several fossils and bones from a different lizard that had an armour, which he called the Hylaeosaurus. By 1835, 3 species of extinct lizards had been discovered. In 1842, Richard Owen studied the skeletons and found they were from a different family than the common lizard. He gave them the name of "terrible lizards" which translates to "Dinos Saurus" in Ancient Greek.