Fossil dinosaur footprint. Fossils appear as rock slowly forms around objects buried in mud. As the rock forms, the shape and anatomy of buried animals and plants can be preserved, including tracks such as these footprints. Trace fossils (ichnofossils) have their own taxonomy. This fossil footprint is that of an unknown dinosaur. It was discovered at a palaeontological site in the region of Porrentruy, Switzerland. Photographed in August 2010.