"How do organisms respond to environmental change? Answering this question is an essential challenge in contemporary scientific research, as it will help us understand—and better prepare for—the rapid pace of current climate change. A striking example of major environmental change in the geological record is the ~30 million years bracketing the Cretaceous-Paleogene boundary (66 million years ago), a time that witnessed a sudden mass extinction that killed off the dinosaurs and an ensuing recovery that vaulted mammals into a dominant role in terrestrial ecosystems during a time of fluctuating climates. This project aims to better understand the end-Cretaceous extinction and Paleogene recovery of mammals by integrating information from a wealth of new fossils, phylogenetic analyses that put these fossils into genealogical context, and cutting-edge quantitative and evolutionary modelling techniques that establish major trends in mammalian evolution and test how these trends were related to environmental change. We will focus on three major mammal groups as exemplars: Metatheria, Taeniodonta, and Pantodonta. We will comprehensively describe the anatomy of five critical species of Paleogene mammals from these groups, which will provide data for genealogical analysis. Next, we will conduct genealogical analyses showing the within-group relationships of these three exemplar groups, and place them on the broader family tree of mammals. Third, we will use these genealogies to quantify rates of species evolution, body size evolution, and anatomical character change in these mammals during the Cretaceous-Paleogene. Fourth, we will evaluate the relationship between Cretaceous-Paleogene mammal diversity and evolutionary rates with changing climates. Taken together, these analyses will test how both sudden and long-term environmental changes affected mammalian evolution, and in doing so will give insight into how modern climate change may affect organisms and ecosystems."