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 1855, geologist Ferdinand Vandeveer Hayden sent fossils to paleontologist Joseph Leidy in Philadelphia. These fossils came from a rock formation called the Great Lignite Formation (now recognized as part of the Lance Formation) near the Grand River in the Nebraska Territory. The collection included two caudal vertebrae and a phalanx.