Experimental taphonomy of macrovertebrate and microvertebrate fossils of the Hell Creek Formation (Latest Maastrichtian) of southeastern Montana

A series of four field and laboratory experiments have been conducted to investigate taphonomic processes such as collection biases, preservation, and taphonomic artifact interpretations on a variety of vertebrate fossils from the Hell Creek Formation (Latest Maastrichtian) of southeastern Montana.;The first experiment investigates the presence of sampling biases in paleoecological reconstructions based on microvertebrate assemblages. Localized accumulations of small vertebrate fossils are relatively common in the Hell Creek Formation (Latest Maastrichtian) and have traditionally been collected using non-standardized field methods, which have resulted in biased interpretations. Results of a quantitative analysis of two common collection methods indicate that the method of collection influences fossil recovery by shape and size, and overall fossil abundance data. These biases may significantly impact paleoecological interpretation.;The second experiment investigates the role of microbial biofilms on the preservation of primary soft tissue in fossil vertebrates. The mineralization of bones and tissues is the most common form of fossilization in the vertebrate record. However, recent studies have presented new data interpreted as preserved dinosaur soft-tissues in the form of integument, feathers, and proteins. These claims have not come without objections, however, with arguments that these artifacts are microbial in origin. This study experimentally examines the role of microbial biofilms on soft-tissue preservation in vertebrate fossils by quantitatively establishing the growth and morphology of biofilms on extant archosaur bone. These results are then compared with soft-tissue extracts from vertebrates from the Hell Creek Formation of southeastern Montana (Latest Maastrichtian) to investigate the role of microbial biofilms on the preservation of fossil bone in a variety of taphonomic settings and suggest new methods of enhancing taphonomic reconstructions. The results indicate that the crystallization of microbial biofilms in decomposing bone in early taphonomic stages may contribute to the preservation of primary soft tissues deeper in the bone structure.;The third and fourth studies investigate the presence and characteristics of lesions in fossil bones. Taphonomic reconstructions are often difficult to perform due to conflicting interpretations of taphonomic artifacts. Behaviors of extinct organisms cannot be witnessed firsthand, but can be inferred in some cases. Differentiation between taphonomic artifacts on fossils and evidence of animal behavior is discussed. A case involving evidence of face biting behaviors on a juvenile tyrannosaur is discussed and the behavioral implications are inferred.;Enigmatic abnormalities, in the form of irregular pitting, commonly occur on pachycephalosaurid crania. Exploratory methods are used to describe and assess these marks, which are alternatively pathologies or taphonomic artifacts. Comparisons are made with similar features present on closely related taxa with the goal of identifying the genesis of these features.;Collectively, these studies serve to advance our knowledge of taphonomic processes and their influence on interpretations of paleoecology and paleobiology. These studies have been conducted through standardized experiments, statistical comparisons, and inferences based on Witmer's Extant Phylogenetic Bracket method.