ABSTRACT

Late Cretaceous dinosaurs of the southeastern U.S. comprise 45 specimens that are divided into four taxonomic groups: tyrannosaurids (12); hadrosaurines (22); ornithomimids (6); and nodosaurs (5). These same taxomomic groups characterize the balance of eastern North American dinosaurs from New Jersey-Delaware-Maryland. The first three taxonomic groups first appear in strata that are significantly older than first appearances in both western North America and the Atlantic Coastal Plain north of North Carolina. These three groups may have entered eastern North America directly from Asian or European habitats via an Atlantic Ocean crossing. In contrast, the southeastern nodosaur group's first appearance is younger than counterparts in western North America and Europe. This group probably entered eastern North America directly from western North America across the Western Interior Seaway. Third-order sea-level fall seems to have affected timing of dinosaurian migrations into and out of eastern North America where the Western Interior Seaway is concerned. Further, Late Cretaceous southeastern paleogeography and thus the amount of dinosaur living space was strongly affected by third-order sea-level changes. There are three modes of occurrence of dinosaurian bones: (1) shallow-marine concentrations; (2) shallow-shelf tempestites; and (3) shelfal accumulations.