Hell Creek Formation
A second footprint that may have been made by a "Tyrannosaurus" was first reported in 2007 by British paleontologist Phil Manning, from the Hell Creek Formation of Montana. This second track measures long, shorter than the track described by Lockley and Hunt. Whether or not the track was made by "Tyrannosaurus" is unclear, though "Tyrannosaurus" and "Nanotyrannus" are the only large theropods known to have existed in the Hell Creek Formation.