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Evolution of Body Size

Graph of sizes of the largest fossils through Earth history.

Sizes of the largest fossils through Earth history. Size maxima are illustrated separately for single-celled eukaryotes, animals, and vascular plants for the Ediacaran and Phanerozoic. The solid line denotes the trend in the overall maximum for all of life. Increases in the overall maximum occurred in discrete steps approximately corresponding to the increases in atmospheric oxygen levels in the mid-Paleoproterozoic and Ediacaran-Cambrian-early Ordovician. From Payne et al., 2009, PNAS.

Research on the evolution of body size in the lab has grown out of observed shifts in maximum and mean size in gastropods and other higher taxa across the end-Permian mass extinction. Our goal is to use time-series of sizes in gastropods and other higher taxa to identify environmental and biological controls on body size evolution. Our current research efforts are focused on the Permian-Triassic and Triassic-Jurassic transitions. We are focused in particular on isolating the contributions of size-biased extinctions and originations and within-lineage size trends to overall shifts in the size distributions of higher taxa through geological time. Isolating these components allows us to better test hypothesized links between environmental change and evolutionary pattern.