The type specimen of "E. regalis" is NMC 2288, consisting of a skull, articulated vertebrae up to the sixth tail vertebra, ribs, partial hips, an upper arm bone, and most of a hind limb. It was discovered in 1912 by Levi Sternberg. The second specimen, paratype NMC 2289, consists of a skull and skeleton lacking the beak, most of the tail, and part of the feet. It was discovered in 1916 by George F. Sternberg. Both skeletons were found in the Horseshoe Canyon Formation (formerly the lower Edmonton Formation) along the Red Deer River of southern Alberta, Canada. The Edmonton Formation lent "Edmontosaurus" its name. The name "Edmontosaurus regalis" (meaning "regal," or, more loosely, "king-sized"), was coined in 1917 by Lawrence Lambe. Lambe found that his new dinosaur compared best to ""Diclonius mirabilis"" specimens (now assigned to "Edmontosaurus annectens"), and drew attention to the size and robustness of "Edmontosaurus regalis". Initially, Lambe only described the skulls of the two skeletons, but returned to the genus in 1920 to describe the skeleton of NMC 2289. The postcrania of the type specimen remains undescribed, still in its plaster jackets.