NEW INSIGHTS INTO INTERPRETING DINOSAUR BEHAVIOR FROM EUBRONTES FOOTPRINTS AT DINOSAUR STATE PARK, ROCKY HILL, CONNECTICUT

Dinosaur State Park (DSP) in Rocky Hill, Connecticut contains about 750 Lower Jurassic therapod tracks ascribed to Eubrontes and interpreted to have been made by a dinosaur similar to Dilophosaurus. The park receives about 40,000 visitors/year and is an important resource for delivering geological content to the residents of Connecticut, primarily school groups. Most published interpretations of the tracks have not changed since originally proposed in the late 1960’s through 1980 despite improvements in our understanding of the controls on track formation, the depositional environments of the East Berlin Formation and lacustrine systems in general, and the biology of Dilophosaurus, the proposed trackmaker.

Traditional interpretations involve Dilophosaurus frequenting a lake margin, occasionally swimming, and preying on fish. Key observations for challenging these interpretations and improving our understanding of the behavior of the DSP trackmakers include: (1) sedimentary structures that suggest the tracks occur in an ephemeral lake environment, (2) the lack of a perennial (fish-bearing) lake correlative to the track layers in nearby outcrops, (3) predictions from modern lacustrine depositional models that do not support the possibility of contemporaneous perennial lakes, (4) track preservational features consistent with walking on moist, but exposed sand, (5) a microbial induced sedimentary structures on the main tracked surface that imply a microbial mat likely enhanced track preservation, (6) so-called “swimmer” tracks that do not resemble tracks from swimming reptiles in the literature, and (7) a recent reassessment of all know Dilophosaurus skeletal material that reveals it was likely an apex predator. These observations suggest that the DSP trackmakers were likely walking on a wet, open sandflat of an ephemeral lake environment. The reason for such a large number of tracks in a small area remains unclear, but the presence of a microbial mat would have enhanced track preservation and allowed the tracks to be impressed over a longer period of time. The tracks previously ascribed to swimming behavior are more likely tracks made under different (drier) sediment conditions, or possibly undertracks from a higher depositional layer.