The conception of Edmontosaurus that emerged included three valid species: the type E. regalis, E. annectens (including Anatosaurus edmontoni, emended to edmontonensis), and E. saskatchewanensis. The debate about the proper taxonomy of the A. copei specimens continues to the present day. Returning to Hatcher's argument of 1902, Jack Horner, David B. Weishampel, and Catherine Forster regarded Anatotitan copei as representing specimens of Edmontosaurus annectens with crushed skulls. In 2007 another "mummy" was announced. Nicknamed "Dakota", it was discovered in 1999 by Tyler Lyson and came from the Hell Creek Formation of North Dakota.
