 The type and only species is M. atherfieldensis.Formerly known as "Iguanodon atherfieldensis", the new genus "Mantellisaurus" was erected for the species by Gregory Paul in 2007.According to Paul, "Mantellisaurus" was more lightly built than "Iguanodon" and more closely related to "Ouranosaurus", making "Iguanodon" in its traditional sense paraphyletic.