ANALYSIS OF TRIDACTYL DINOSAUR TRACKS FROM THE EARLY JURASSIC KAYENTA FORMATION, CEDAR CITY, UTAH, USA

Multiple tridactyl dinosaur tracks were recently discovered on the upper surface of sandstone beds within the Main Body member of the Kayenta Formation in Cedar City, Utah, near the western entrance to Cedar Canyon on Utah State Route 14. The Kayenta Formation is an Early Jurassic unit well known in the region for dinosaur and other vertebrate track sites and rare body fossils. We measured a fifty meter stratigraphic section within the formation that comprises ripple cross laminated and trough cross bedded fine and very fine sandstone and interbedded with siltstone, indicative of a fluvially-dominated depositional environment in which sandy bars formed in channels or as sheet flood deposits, interbedded with relatively thin layers of highly oxidized floodplain and lacustrine siltstone and rare microbial mats.

Two track horizons were found on the upper surfaces of sandstone beds at two different stratigraphic positions. A minimum of two complete tracks have been found within the lower bed and a minimum of three complete tracks on the upper bed. All tracks are tridactyl pes imprints most likely made by theropod dinosaurs. There are two distinct populations of small tracks. The first population has an average maximum track length of 19.5 cm from the tip of digit III to the “heel”, and divarication angles of 40-60°, with distinct sharp claw impressions at the end of each toe. The second population has an average maximum track length of 11.5 cm, and divarication angles of 25-40°. These tracks have wider digits and less distinct claws impressions. These smaller track populations are tentatively identified as Kayentapus or Carmelopodus, with potential reinterpretation as Grallator. The upper bed also contains a significantly larger specimen, at 43 cm total track length, which resembles Eubrontes. Eubrontes and Grallator are very common in the region within both the Kayenta Formation and the underlying Moenave Formation.