Trace fossil

Trace fossils, also called ichnofossils (, meaning "trace" or "track"), are structures preserved in sedimentary rocks that record biological activity. While we are most familiar with relatively spectacular, fossilized hard-part remains such as shells and bones (known as body fossils), trace fossils are often less dramatic, but nonetheless very important. Strictly defined, trace fossils must reflect both the anatomy of their maker in some way, and be the result of behaviour. Sedimentary structures made by empty shells rolling along the sea floor are thus excluded (as "death marks"), as are structures such as stromatolites that, although the result of behaviour, do not reflect the anatomy of their maker. Spun coccoons and spiders webs are considered to be trace fossils, as they are manipulated by their makers after secretion; egg cases, on the other hand, are not. Trace fossils include burrows (such as Chondrites), borings, ichnites (footprints and track marks), Zoophycus feeding marks, trails (such as Cruziana scratched by trilobites), coprolites (fossilized droppings) and other gut-derived objects, and rhizoliths or rhizocretions (the fossil remains of roots).
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