Land Mammal Faunas of North America Rise and Fall During the Early Eocene Climatic Optimum

Denver Museum of Nature & Science Annals, No. 1, September 1, 2009 Climatic warming at the beginning of the Early Eocene Climatic Optimum (EECO) resulted in major increases in plant diversity and habitat complexity reflective of temporally unique, moist, paratropical conditions from about 53–50 Ma in the Western Interior of North America.