Befitting a genus with a confusing taxonomic history, the name of this genus is based on an error. David Gillette and David Thomas collected the type and only known specimen from what was thought to be the Naashoibito Member of the Kirtland Formation, the youngest member of the Kirtland; this was commemorated in the name. Instead, it came from the older, late Campanian-age De-na-zin Member. Horner described the skull in 1992 as that of an immature "Kritosaurus", using it as evidence that "Gryposaurus" was different from "Kritosaurus". At the same time, Hunt and Lucas were describing the postcrania as belonging to "Edmontosaurus saskatchewanensis". When the disconnect became apparent, Hunt and Lucas gave the specimen its own generic name, because the skull did not agree with an edmontosaur, and they considered "Kritosaurus" indeterminate and thus not usable.