LATE CRETACEOUS DINOSAUR TRACKS FROM THE IRON SPRINGS FORMATION, IRON COUNTY, UTAH

The Parowan Gap dinosaur track site, located in Iron County, Utah, contains over one hundred natural casts of individual non-avian theropod and ornithopod dinosaur tracks preserved in sandstones and siltstones of the Late Cretaceous (Santonian-Campanian) Iron Springs Formation. For this study the authors returned to the area to survey for and describe previously unidentified tracks. Most tracks from this new study occur as casts found on the basal surfaces of in situ sandstones deposited by braided and meandering rivers on the coastal plain of the Western Interior Seaway, with a few specimens from fallen talus blocks. Associated plant fossils include angiosperm and coniferous gymnosperm leaf impressions and iron-petrified wood, as well as root traces in mudstones. The results comprise tracks from a minimum of at least three ichnotaxa including Ornithomimipus, Caririchnium, and Ceratopsipes. The Ornithomimipus specimen likely represents a small theropod dinosaur (total track length of 21 centimeters). This specimen is of great interest because theropod tracks are less common in the Iron Springs Formation, with a total of seven tracks reported from previous studies. Another interesting find is a Caririchnium trackway, which may represent the movement of a hadrosaurid dinosaur along a shallow or abandoned channel on the floodplain. We identified two Ceratopsipes tracks in a fallen block of sandstone. The pair of tracks are significant because they are the second set from the ichnotaxa found at Parowan Gap, and together they represent the oldest ceratopsian tracks in Utah.