CRETACEOUS PLANT-ANIMAL INTERACTIONS: CAN DISTRIBUTION PATTERNS OF HERBIVOROUS DINOSAURS AND PLANTS BE USED TO TEST FOR CO-EVOLUTION

Previous studies of potential co-evolution between herbivorous dinosaurs and plants have generally relied on analyses of specific morphological features (e.g., advances in tooth/jaw structure, size/shape of diaspores, etc.). An alternative is to test this potential relationship through comparison of stratigraphic and geographic co-occurrence of these groups. This study uses the degree of overlap in the geographic distribution of herbivorous dinosaurs (sauropod, ornithischia) and coexisting plant groups (conifers, angiosperms, pteridophytes, other gymnosperms) as proxies for co-occurrence, using both an interval in the early-middle Cretaceous and at the end of the Cretaceous. Distribution patterns are derived from compilations of known age and locality data from North American fossil localities; dinosaur data were provided by D. Weishampel, plant data were collected from primary literature. The data were assessed for degree of similarity using second-order nearest-neighbor and bivariate K analyses. The results indicate no strong correlation between the occurrence of sauropods and either conifers or angiosperms, but did indicate significant similarity between the distribution of later Cretaceous ornithischians and angiosperms relative to other plant groups. Although North America has a relatively large number of localities reported, data are often sparse and scattered, with the exception of localities along the margins of the Western Interior Seaway. Further work is need to address this depositional bias.