Was theEubrontesTrack Maker Gregarious? Testing the Herding Hypothesis at Powder Hill Dinosaur Park, Middlefield, Connecticut

Abstract

Abstract The theropod footprint taxon Eubrontes is common in Early Jurassic rocks of the Hartford Basin. Aligned Eubrontes trackways at one site in Holyoke, Massachusetts, have led to the hypothesis that the track makers were gregarious; however, trackways are not aligned at several other sites. To test the gregariousness hypothesis, we measured trackway orientations at Powder Hill Dinosaur Park in Middlefield, Connecticut, where exposed rocks were deposited in an ephemeral lake environment, and compared these orientations to those of two additional track sites from similar sedimentary facies. The Eubrontes trackways produced in the ephemeral lake environments have no preferred orientation and provide no evidence of gregarious behavior. We suggest that the alignment of tracks in Holyoke reflects behavior in response to environmental settings rather than group behavior. Trackways may be aligned next to large, permanent lakes because of shoreline-parallel travel, but random orientations characterize other h...