Trace fossils
Trace fossils are preserved evidence of what organisms did, rather than the preserved bodies of the organisms themselves. Footprints, burrows, trails, nests, bite marks, root traces, and coprolites can reveal movement, feeding, hiding, nesting, and interactions in ancient environments.
What trace fossils are
Trace fossils are geological records of biological activity. A dinosaur footprint, a worm burrow, a root trace, a feeding trail, or fossilized dung records something an organism did. This makes trace fossils different from body fossils such as bones, shells, teeth, leaves, or pollen.
Body fossils versus behavior
A body fossil can show anatomy. A trace fossil can show behavior. A trackway may show how an animal moved, a burrow may show how an organism lived in sediment, and a coprolite may preserve clues about diet. Trace fossils can sometimes record soft-bodied animals that left few or no body fossils.
How traces are preserved
Traces are preserved when sediment records an activity before it is erased. A footprint may be covered by another layer of sediment. A burrow may be filled with different material from the surrounding rock. A feeding trail may be hardened and buried. Later compaction, cementation, erosion, and exposure can turn that activity into a fossil record.
Footprints and trackways
Footprints and trackways can reveal direction of travel, stride length, gait, group movement, substrate conditions, and sometimes approximate body size. They rarely identify an exact species by themselves. A footprint is often given an ichnotaxon name based on its form, because the track maker may not be known with certainty.
Burrows, borings, and trails
Burrows and trails are common trace fossils in sedimentary rocks. They can show how animals moved through mud, sand, or seafloor sediment. Borings record organisms drilling or rasping into hard surfaces such as shells, wood, or rock. These traces help reconstruct oxygen levels, sediment consistency, water depth, energy, and ecological activity.
Coprolites and feeding traces
Coprolites are fossilized feces. They may preserve bones, scales, pollen, plant fragments, parasites, or chemical clues about diet and digestion. Bite marks, scrape marks, drill holes, and gnaw traces can show predator-prey relationships, scavenging, grazing, or other interactions that body fossils alone might miss.
Limits and uncertainty
Trace fossils are powerful but tricky. Similar traces can be made by different organisms, and one organism can make different traces depending on behavior, sediment, and water conditions. A trace can be preserved without the animal's body nearby. Good interpretation uses shape, sedimentary context, associated fossils, modern analogs, and careful uncertainty.
Why it matters
Trace fossils matter because they add behavior to the fossil record. They reveal how organisms moved, fed, sheltered, reproduced, and changed sediment. They also help paleontologists study ancient ecosystems, early animal activity, mass-extinction recovery, and environments where body fossils are rare.