I propose the study the dental microwear of Paleogene ungulates of North America to test hypotheses relating the paleodietary ecology of mammals to dental morphology and climate change. The fossil record documents the repeated evolution of lophodont dentitions from more bunodont forms. This trend is thought to correspond to a dietary shift from frugivory to folivory necessitated by global cooling, increasing seasonality, and associated habitat changes. The dental microwear methodology will be used to predict the diets of extinct species, to reconstruct the ecological profiles of successive faunas, and to trace the early dietary histories of major ungulate lineages, including the modern orders Artiodactyla and Perissodactyla. The dental microwear methodology liberates dental morphology from the task of making paleodietary inferences, thus allowing us to examine paleoecological change independent of morphological change and to track paleodiets at finer temporal scales. Solounias is largely responsible for developing the methods that will be used, while Mihlbachler has taken a role in further developing many aspects of these methods. The first year will be spent compiling casts of teeth for use wear analysis, curation of the cast library, and collection and analysis of data. Data analysis and dissemination of results will be completed in year two. This project will address two basic hypotheses that we believe are critical to mammalian evolutionary dietary paleoecology: Hypothesis 1: The evolution of lophodonty among Paleogene ungulates and ungulate-like mammals corresponds to a widespread shift from frugivory/omnivory in the beginning of the Paleogene to predominantly folivory by the close of the Paleogene. If dental microwear contradicts or is only loosely associated with dental classifications, it is a strong signal that mammalian paleodietary ecology should be more carefully evaluated, drawing evidence not just from dental morphology, but from dental use wear data (such as microwear) and other morphologically independent methods such as stable isotopes. Hypothesis 2: Mammalian paleodietary responses to climate changes occurred on time scales that are much finer than that which is suggested by trends in dental macroevolution. The Bighorn and Clark?s Fork Basins document a critical time period near the Paleocene-Eocene boundary. This critical time interval documents a rapid increase in CO2, the appearance of many immigrant taxa, and dwarfing events among several lineages. The dense sampling of mammals with high stratigraphic resolution through this interval afford us a rare opportunity to study paleoecological change during a critical interval in mammalian evolution at a scale of temporal resolution in which greenhouse warming processes and many evolutionary processes (speciation, extinction) are known to operate. In addition to developing a better understanding of evolution-ecology-climate dynamics, other broad impacts of this proposal are to expose a number of undergraduates and medical students to the scientific process to facilitate further research along similar lines and to provide results for an NSF funded website that is currently under development at the AMNH. Students will be hired to assist with the dental cast collection resulting from this proposal, and the entire collection of casts on modern and Miocene mammals collected by Solonious from prior NSF grants. These casts will be cataloged and made available to those who wish to conduct similar research in mammalian paleoecology.
