English: Lockeia - bivalve trace fossils in sandstone from the Silurian of Tennessee, USA. (bedding plane view)

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.

The traces shown above are consistent with Lockeia, a type of dwelling burrow made by bivalves (= clams). Bivalves are bilaterally symmetrical molluscs having two calcareous, asymmetrical shells (valves) - they include the clams, oysters, and scallops. In most bivalves, the two shells are mirror images of each other (the major exception is the oysters). They occur in marine, estuarine, and freshwater environments. Bivalves are also known as pelecypods and lamellibranchiates.

Bivalves are sessile, benthic organisms - they occur on or below substrates. Most of them are filter-feeders, using siphons to bring in water, filter the water for tiny particles of food, then expel the used water. The majority of bivalves are infaunal - they burrow into unlithified sediments. In hard substrate environments, some forms make borings, in which the bivalve lives. Some groups are hard substrate encrusters, using a mineral cement to attach to rocks, shells, or wood.

The fossil record of bivalves is Cambrian to Recent. They are especially common in the post-Paleozoic fossil record.

Stratigraphy: out-of-place rock likely derived from the Clinch Formation, Lower Silurian

Locality: rock in wall at Veterans Overlook, southern side of Rt. 25E, near the top of Clinch Mountain, northeastern Grainger County, northeastern Tennessee, USA (36° 20' 58.78" North latitude, 83° 23' 37.59" West longitude) - wall rock is of unknown provenance, but possibly (probably?) derived from Clinch Mountain itself.