PRESERVATIONAL AND MORPHOLOGICAL VARIATIONS IN THEROPOD TRACKS AND TRACKWAYS ON A MIDDLE JURASSIC TIDAL FLAT: IMPLICATIONS FOR PALEOBIOLOGICAL AND PALEOECOLOGICAL ANALYSIS

The fossilized footprints of dinosaurs provide an incredible opportunity to study the interactions of these prehistoric beasts with their environment. Often these "live-action" glimpses of the past are tantalizingly small, consisting of only a few isolated tracks or scattered trackways. However, this is not the case in northern Wyoming where 1000s of dinosaur tracks have been discovered in the Bathonian Canyon Springs Member of the lower Sundance Formation; providing the first information on a new dinosaur community and its paleonenvironment. Intensive study of a large vertebrate ichnology data set consisting of detailed measurements, descriptive observations, statistical calculations, and extensive graphic documentation allows for a unique glimpse of Middle Jurassic paleoecology and a paleobiology. Over 30,000 attributes recorded from the tridactyl pes impressions of hundreds of small- to medium-sized theropod dinosaurs have been integrated with innovative photographic and survey documentation data. Concurrent observations of the track-bearing, peritidal limestone provides clues to the understanding of the variations of the substrate through time and space. Several different track generation episodes are recognized. In addition, dramatic differences in track morphology both within and between trackways have been noted due to individual trackmaker characteristics, undertrack preservation, lateral and vertical substrate variations, and differential weathering. Multivariant analysis of the ichnology data supports interpretations about the family structure and community dynamics of gregarious dinosaurs walking in thixotropic sediments. The interpretations of these intricate relationships were only undertaken after careful, systematic documentation and study, so as to better understand the behavioral complexities of the extinct fauna.