image: This outcrop shows major shell concentrations of Miocene age (approximately 20 million years old), exposed in the Calvert Cliffs along the western shore of Chesapeake Bay in Maryland. This image relates to an article that appeared in the October 6, 2006, issue of the journal Science, published by AAAS. The study, by Dr. David Jablonski of University of Chicago and colleagues, was titled "Out of the Tropics: Evolutionary Dynamics of the Latitudinal Diversity Gradient." view more
Credit: Photo provided by Susan M. Kidwell, University of Chicago, via <i>Science</i>-AAAS.