Therosaurus is a genus of ornithopod dinosaurs containing the single species Therosaurus anglicus, previously known as Iguanodon anglicus. Though important in the history of paleontology as being among the first dinosaur fossils ever named and described, because the species name Iguanodon anglicus was based on very fragmentary fossil remains (a collection of teeth), the name Iguanodon was later officially transferred to a different animal. This left Therosaurus (Ancient Greek: θήρα 'thera', hunting of wild beasts; Latin: anglicus, English) as the oldest available genus name for the genus containing historic but dubious teeth first discovered by Gideon Mantell in England.