Fossilized evidence of animal behavior, also known as ichnofossils, biogenic sedimentary structures, bioerosion structures, or lebensspuren. The fossils include burrows, trails, and trackways created by animals in unconsolidated sediment (see illustration), as well as borings, gnawings, raspings, and scrapings excavated by organisms in harder materials, such as rock, shell, bone, or wood. Some workers also consider coprolites (fossilized feces), regurgitation pellets, burrow excavation pellets, rhizoliths (plant root penetration structures), and algal stromatolites to be trace fossils. See also Stromatolite.

Spirorhaphe) and a meshlike network of tunnels (Paleodictyon). Tertiary, Austria. (Photograph by W. H?ntzschel)" src="http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE703400FG0010.gif">
Agrichnial farming traces (burrows produced in order to farm or trap food inside the sediment) of unknown organisms, including a double-spiral tunnel (Spirorhaphe) and a meshlike network of tunnels (Paleodictyon). Tertiary, Austria. (Photograph by W. H?ntzschel)