The first known fossil remains that may belong to "Edmontosaurus regalis" were named "Trachodon cavatus" in 1871 by Edward Drinker Cope (the name is spelled in more recent sources as "Trachodon avatus" or even "Trachodon atavus"). This species was assessed without comment as a synonym of "Edmontosaurus regalis" in two reviews, although "atavus" predates "regalis" by several decades. In 1874 Cope named but did not describe "Agathaumas milo" for a sacral vertebra and shin fragments from the late Maastrichtian-age Upper Cretaceous Laramie Formation of Colorado. Later that same year, he described these bones under the name "Hadrosaurus occidentalis". The bones are now lost. As with "Trachodon atavus", "Agathaumas milo" has been assigned without comment to "Edmontosaurus regalis" in two reviews, although predating "regalis" by several decades. Neither species has attracted much attention; both are absent from Lull and Wright's 1942 monograph, for example. A third obscure early species, "Trachodon selwyni", described by Lawrence Lambe in 1902 for a lower jaw from what is now known as the Dinosaur Park Formation of Alberta, was erroneously described by Glut (1997) as having been assigned to "Edmontosaurus regalis" by Lull and Wright. It was not, instead being designated "of very doubtful validity." More recent reviews of hadrosaurids have concurred.