TURONIAN TRACKWAY DISPARITY AT MARY ANN’S TRACKSITE, CENTRAL UTAH

The Turonian Ferron Sandstone of central Utah has only a few recorded examples of vertebrate tracks and only one previously reported dinosaur trackway. Here, in this initial study, we report data collected from three trackways within the Ferron Sandstone at Mary Ann’s Tracksite. The tracks of the tracksite are all tridactyl pes molds within a light tan to white well-rounded and well-sorted quartz arenite. Trackway 1 represents the largest tracks on the tracksite with nine tracks averaging 37 cm in length. This trackway has a calculated approximate hip height of 1.46 m and speeds between 2.7 - 5.98 km/hr (4.0 km/hr average) indicating relatively slow locomotion for its size, which is common in larger animals. Trackway 2 contains 21 tracks with a calculated average hip height of 1.1 m and an average speed of 4.7 km/hr indicating a slow walking pace. Trackway 3 contains 7 tracks with lengths of 22.5 cm on average and a calculated average hip height of 0.9 m. The animal’s speed increased across the trackway by 5.0 - 6.6 km/hr from the initial to last recorded track. This indicates the animal in Trackway 3 achieved a trotting speed (9.4 km/hr). The change in speed is accompanied by a change in track morphology of more posterior disconnection and likely increase in the shift of the weight onto the anterior portion of the toes with increasing speed. Overall, the smallest dinosaur showed the fastest movement whereas the largest showed the slowest, which may have implications about body size, locomotion related to substrate, or predation pressure.