Understanding the paleoecology and evolution of cetaceans in the eastern North Pacific Ocean during the Neogene

Living whales and dolphins (or cetaceans) play important roles in ocean ecosystems. However, in the broader scope of marine metazoan history, cetaceans are relative newcomers in marine ecosystems. Within 50 million years, they have transitioned from ecological nonexistence (terrestrial ancestry) to trophic dominance. Understanding the evolution of cetaceans and their ecological role in marine ecosystems requires a thorough evaluation of the cetacean fossil record. This dissertation specifically addresses the ecological origin of crown cetaceans by developing a set of tools and approaches to evaluate their paleoecology during the Neogene.;Chapter 1 highlights the importance of historical approaches in studying large marine vertebrates. I review the ecology of living cetaceans, focusing on studies in the North Pacific Ocean, as well as the quality of the cetacean fossil record along the western margin of North America. Notably, the middle Miocene preserves the greatest richness of fossil cetaceans, even accounting for rock area and collection biases.;Chapter 2 uses several diversity metrics to compare the death assemblage of cetaceans along the continental United States coastline (i.e., the historical record of cetacean strandings) with the living community in the adjacent waters of the Eastern North Pacific Ocean. At decadal time scales and with coastlines >1000 km in length, the death assemblage faithfully records the taxonomic composition, richness, and abundance of living cetacean communities.;Chapter 3, which is co-authored with Simon Sponberg, uses a comprehensive database of skull and length measurements from living cetacean species to generate multivariate and phylogenetically controlled regression equations that predict body size in fossil cetaceans. We test these predictions with unique fossils that preserve total length, and then reconstruct body size for select fossil mysticetes and odontocetes.;Chapter 4 assesses the paleoecology of cetaceans from the middle Miocene Sharktooth Hill bonebed of Kern County, California. I describe the geological context, taphonomy and the taxonomic assemblage of fossil cetaceans preserved in the bonebed, and use specific diversity metrics (e.g., relative abundance, body size categories) to compare the structure of this fossil cetacean assemblage with the death assemblage and living community that currently inhabits the Eastern North Pacific Ocean.