Crocodilian footprint in quartzose sandstone, Cretaceous of Colorado, USA.

Trace fossils are any indirect evidence of ancient life. They refer to features in rocks that do not represent parts of the body of a once-living organism. Traces include footprints, tracks, trails, burrows, borings, and bitemarks. Body fossils provide information about the morphology of ancient organisms, while trace fossils provide information about the behavior of ancient life forms. Interpreting trace fossils and determination of the identity of a trace maker can be straightforward (for example, a dinosaur footprint represents walking behavior) or not. Sediments that have trace fossils are said to be bioturbated. Burrowed textures in sedimentary rocks are referred to as bioturbation. Trace fossils have scientific names assigned to them, in the same style & manner as living organisms or body fossils.

Dinosaur Ridge, west of Denver, Colorado, is famous for having common dinosaur bones and dinosaur footprints in Jurassic- & Cretaceous-aged rocks. The eastern side of Dinosaur Ridge has an impressive bedding plane with numerous dinosaur tracks. In addition to dinosaur trace fossils, eastern Dinosaur Ridge also has some remarkable crocodilian traces. Shown above is a footprint made by a walking Cretaceous crocodilian.

Stratigraphy: Dakota Sandstone, upper Lower Cretaceous