Triceratops dinosaur footprint in sandstone in the 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.

Seen here is the underside of a vertically-oriented, nonmarine sandstone bed in Golden, Colorado. The bulging structure in the rock is a ceratopsian dinosaur footprint assigned to Triceratops. The rocks at this site were tectonically tilted during the Laramide Orogeny, an ancient mountain-building event that resulted in the formation of the true Rocky Mountains.

Stratigraphy: Laramie Formation, Maastrichtian Stage, upper Upper Cretaceous