The ichnological record of vertebrate consumption from the Upper Jurassic Morrison Formation of Western North America with description of a new dentalite and revision of the ichnogenus Machichnus

The Upper Jurassic Morrison Formation is famous for its vertebrate fauna, notably dinosaurs, but it yields a relatively depauperate vertebrate ichnofauna, except for tracks. The track ichnofauna is quite extensive, but traces related to consumption are uncommon. Dentalites are known from several Morrison sauropods but only from a few theropods and other non-sauropod herbivorous dinosaurs. We restrict the dentalite ichnogenus Machichnus to include only the ichnospecies M. regularis, M. multilineatus and Machichnus inrosus, which represent rodent gnawing. Morsichnus igen. nov. is introduced to include the raking traces Morsichnus (Machichnus) bohemicus, Morsichnus (Machichnus) fatimae and Morsichnus (Machichnus) dimorphodon. Morsichnus deinodentatus igen. et isp. nov. represents the traces of the biting of large theropods. We coin the term Seeker Effect (Seeker Fieldwork Effect, Seeker Collections Effect) to recognize the importance in the fossil record of fossils being found when sought. Recent work suggests that the Seeker Collection Effect may reveal many more Morrison dentalites when existing collections are re-examined, and the same is true for molalites. Regurgitalites, consumulites and coprolites are very uncommon due to taphonomic megabiases. Pabulites and digestilites are recent concepts that have not been applied to the Morrison Formation trace-fossil record. Micturalites are absent or rare in the Morrison Formation, as they are elsewhere. Claims of Morrison dinosaur gastroliths are largely based on polished siliceous clasts that lack a skeletal association, so these are doubtful records of gastroliths. Theropod tracks from two large dinosaur quarries (Howe Quarry, Something Interesting Quarry) may represent scavenging by carnivores.