File:Asteriacites starfish burrow (Pennsylvanian; Kansas, USA) 4.jpg

English: Asteriacites sp. - starfish trace fossil from the Pennsylvanian of Kansas, 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.

One of the most distinctive invertebrate trace fossils around is Asteriacites, which is a burrow made by a starfish (Phylum Echinodermata, Class Asteroidea) or brittle star (Phylum Echinodermata, Class Ophiuroidea). Starfish are vagrant, benthic, predatory echinoderms. They have a multielement skeleton composed of numerous, small, calcitic plates. Most starfish are pentaradial (they have 5 arms), but some species have 6 or more arms.

The starfish burrow seen here is a convex hyporelief on the underside of a very fine-grained sandstone from Kansas. Fine striations along the impressions of the arms represent digging motions by the tube feet. Even the depression in the mouth area shows scratches made by movements of the mouth frame.

Stratigraphy: unrecorded Pennsylvanian-aged unit

Locality: unrecorded/undisclosed site in Kansas, USA