Thespesius

Thespesius (meaning "wondrous one") is a dubious genus of hadrosaurid dinosaur from the late Maastrichtian-age Upper Cretaceous Lance Formation of South Dakota.

==History== In 1855 geologist Ferdinand Vandeveer Hayden sent a number of fossils to paleontologist Joseph Leidy in Philadelphia. Hayden had collected them from the surface of a rock formation then known as the Great Lignite Formation (now recognized as part of the Lance Formation) in the Nebraska Territory, near the Grand River (present-day South Dakota). Among them were two caudal vertebrae and a phalanx. In 1856 Leidy named the type species Thespesius occidentalis for these three bones. The generic name is derived from Greek θεσπεσιος, thespesios, "wondrous", because of the colossal size of the remains. Leidy avoided using the suffix "saurus" in the genus name because Vandeveer Hayden had claimed the bones came from a layer from the Miocene so there was a chance that the animal would turn out to be a mammal, though Leidy himself was convinced it was a dinosaurian. The specific name means "western" in Latin.