Northward range extension of a diminutive-sized mammal (Ectocion parvus) and the implication of body size change during the Paleocene-Eocene Thermal Maximum

► A global warming event marks the Paleocene-Eocene boundary. ► Diminutive sized mammals occur at the Paleocene-Eocene boundary in Wyoming. ► Correlated Paleocene-Eocene boundary between Colorado and Wyoming. ► Discovered diminutive mammal species in Colorado prior to boundary. ► Proposed that the species extended its range northward during global warming event.