My research uses the fossil record of arthropods, especially trilobites, but also other taxa including mollusks, to reconstruct evolutionary patterns in order to gain insight into the nature of the evolutionary process. I am particularly interested in research approaches that use biogeography, phylogenetics, and ecological niche modeling. I have also considered various topics in macroevolutionary theory including levels of selection, punctuated equilibria and mechanisms of stasis, evolutionary and adaptive radiations, the role abiotic as opposed to biotic factors play in governing macroevolution, and the effects of past, present, and future climate change on ecology and evolution. In addition, my research focuses on macroevolutionary patterns and processes during key episodes in the history of life such as the Cambrian radiation, the end Ordovician mass extinction, and the Late Devonian biodiversity crisis.