Ecometric Estimation of Present and Past Climate of North America Using Crown Heights of Rodents and Lagomorphs

Document Type


Publication Date



Studies of large herbivorous mammal (ungulate) communities have revealed an association between increased tooth crown height (hypsodonty) and a shift to more arid environments over the Cenozoic. Ecometric analyses have also been used to examine the relationship between current climate conditions and crown height of these communities, and very successfully used to estimate past precipitation. Small herbivorous mammals (rodents and lagomorphs) have been shown to similarly adapt to changing habitats over the Cenozoic, but did so millions of years earlier than larger mammals. Here, we have utilized ecometric methods to examine the relationships between rodent and lagomorph crown height and diversity with current climate conditions, finding strong correlations of community structure parameters with climate, particularly mean annual temperature, maximum temperature of the warmest month, and minimum temperature of the coldest month. We applied the resultant regression equations to well-sampled fossil localities from North America, spanning over 37 million years, allowing estimation of climate conditions in deep time. As expected, estimates show a general pattern of decrease in both precipitation and temperature across North America from 37 Ma to the present. Overall, these findings provide a new broadly-applicable proxy for estimation of Cenozoic climate conditions at a local scale.