page_title: Trace fossil
section_title: Common ichnogenera
hierarchical_section_title: Trace fossil / Common ichnogenera
caption_attribution_description: Thalassinoides burrows produced by crustaceans; the Middle Jurassic, Makhtesh Qatan, southern Israel.
context_page_description: A trace fossil, also ichnofossil, is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, which are the fossilized remains of parts of organisms' bodies, usually altered by later chemical activity or mineralization. Ichnology is the study of such trace fossils and is the work of ichnologists.
  Trace fossils may consist of impressions made on or in the substrate by an organism. For example, burrows, borings, urolites, footprints and feeding marks and root cavities may all be trace fossils.
  The term in its broadest sense also includes the remains of other organic material produced by an organism; for example coprolites or chemical markers. However, most sedimentary structures are not produced through the behaviour of an organism and thus are not considered trace fossils.
  The study of traces - ichnology - divides into paleoichnology, or the study of trace fossils, and neoichnology, the study of modern traces. Ichnological science offers many challenges, as most traces reflect the behaviour—not the biological affinity—of their makers.
context_section_description: Anoigmaichnus is a bioclaustration. It occurs in the Ordovician bryozoans. Apertures of Anoigmaichnus are elevated above their hosts' growth surfaces, forming short chimney-like structures.
  Arachnostega is the name given to the irregular, branching burrows in the sediment fill of shells. They are visible on the surface of steinkerns. Their traces are known from the Cambrian period onwards.
  Asteriacites is the name given to the five-rayed fossils found in rocks and they record the resting place of starfish on the sea floor. Asteriacites are found in European and American rocks, from the Ordovician period onwards, and are numerous in rocks from the Jurassic period of Germany.
  Burrinjuckia is a bioclaustration. Burrinjuckia  includes outgrowths of the brachiopod's secondary shell with a hollow interior in the mantle cavity of a brachiopod.
  Chondrites (not to be confused with stony meteorites of the same name) are small branching burrows of the same diameter, which superficially resemble the roots of a plant. The most likely candidate for having constructed these burrows is a nematode (roundworm). Chondrites are found in marine sediments from the Cambrian period of the Paleozoic onwards. They are especially common in sediments which were deposited in reduced-oxygen environments.
  Climactichnites is the name given to surface trails and burrows that consist of a series of chevron-shaped raised cross bars that are usually flanked on either side by a parallel ridge. They somewhat resemble tire tracks, and are larger (typically about four inches wide) than most of the other trace fossils made by invertebrates. The trails were produced on sandy tidal flats during Cambrian time. While the identity of the animal is still conjectural, it may have been a large slug-like animal - its trails produced as it crawled over and processed the wet sand to obtain food.
  Cruziana are excavation trace marks made on the sea floor which have a two-lobed structure with a central groove. The lobes are covered with scratch marks made by the legs of the excavating organism, usually a trilobite or allied arthropod. Cruziana are most common in marine sediments formed during the Paleozoic era, particularly in rocks from the Cambrian and Ordovician periods. Over 30 ichnospecies of Cruziana have been identified. See also Isopodichnus.
  Entobia is a boring produced by endolithic clionaid sponges consisting of galleries excavated in a carbonate substrate; often has swollen chambers with connecting canals.
  Gastrochaenolites are clavate (club-shaped) borings also produced in calcareous hard substrates, usually by bivalves.
  Oikobesalon is an unbranched, elongate burrow with single-entrance and circular cross-section produced by terebellid polychaetes. They are covered with thin lining which has a transverse ornamentation in the form of fusiform annulation.
  Petroxestes is a shallow groove boring produced by mytilacean bivalves in carbonate hard substrates.
  Protichnites consists of two rows of tracks and a linear depression between the two rows. The tracks are believed to have been made by the walking appendages of arthropods. The linear depression is thought to be the result of a dragging tail. The structures bearing this name were typically made on the tidal flats of Paleozoic seas, but similar ones extend into the Cenozoic.
  Rhizocorallium is a type of burrow, the inclination of which is typically within 10° of the bedding planes of the sediment. These burrows can be very large, over a meter long in sediments that show good preservation, e.g. Jurassic rocks of the Yorkshire Coast (eastern United Kingdom), but the width is usually only up to 2 cm, restricted by the size of the organisms producing it. It is thought that they represent fodinichnia as the animal (probably a nematode) scoured the sediment for food.
  Rogerella is a small pouch-shaped boring with a slit-like aperture currently produced by acrothoracican barnacles.
  Rusophycus are bilobed "resting traces" associated with trilobites and other arthropods such as horseshoe crabs.
  Skolithos: One well-known occur
caption: Thalassinoides, burrows produced by crustaceans, from the Middle Jurassic, Makhtesh Qatan, southern Israel
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