Distinguishing True Tracks from Undertracks and Overtracks at Dinosaur State Park, Rocky Hill, Connecticut

About 750 Eubrontes footprints occur on three stratigraphic layers in the Jurassic East Berlin Formation at Dinosaur State Park in Rocky Hill, Connecticut (USA). Several trackways and individual tracks are preserved on multiple sedimentary layers, as true tracks on one layer and as their corresponding transmitted undertracks or overtracks on another, making the park an ideal place for investigating morphological, stratigraphic, and sedimentological criteria for distinguishing true tracks from undertracks and overtracks. True tracks are deeper and preserve more anatomical detail than corresponding undertracks and overtracks. Sedimentary features associated with tracks, such as skin impressions, displacement rims, radial fractures, and structural deformation features, typically form on the tracked surface but may be transmitted to layers below. Of these features, only displacement rims occur at Dinosaur State Park, but even they are uncommon. The relationship between the footprint and sedimentary structures is used to determine the relative timing of track registration. Wave ripples on tracked surfaces predate the tracks and are destroyed by the trackmakers, but ripples are preserved in overtracks and some undertracks. Microbial mat formation enhanced preservation of tracks by binding sediment, decreasing the sediment plasticity, and minimizing erosion after track registration. Internal laminae in beds at Dinosaur State Park can reliably identify the tracked surface. Beds below the tracked surface preserve deformation associated with vertical compression when the track was registered. Beds overlying the tracked surface preserve distinct lateral and vertical sediment fill patterns. These criteria are used to assign tracks to a specific tracked surface to identify which dinosaur footprints were registered roughly contemporaneously. This is critical for understanding paleoecology, investigating possible gregarious behavior of trackmakers, determining the type of locomotion (walking, running, or swimming), and exploring other trackmaker behavior in their environment. Observations from Dinosaur State Park can be applied to other tetrapod tracksites.