Here is an interesting fossil that resides in the Bellarmine University Geoscience Collection located in Louisville, Kentucky. It is a tortoise shell fossil found in the Brules Formation of Nebraska. The fossil appears to be from the Stylemys nebrascensis. The creature roamed the Earth during the Oligocene Epoch (about 30 million years ago.
Learn more about this type of fossil at the University of Colorado Boulder Museum of Natural History web site.