ichnology

Ichnology, from the Greek ichnos for trace, is the scientific study of traces left by organisms as preserved in rocks, soils, or sediments. Traces, or trace fossils (ichnofossils), record activities such as locomotion, feeding, dwelling, and interaction with the substrate. Common examples include footprints, trackways, burrows and borings, dwelling structures, feeding marks, nests, and sediment reworking by organisms. Ichnology emphasizes behavior and ecology rather than the anatomy of the producer, so trace fossils are often attributed to one or more likely producers, or left as indeterminate traces.

Because the same organism can produce different traces and similar traces can be produced by different organisms, ichnology uses its own nomenclature—ichnogenera and ichnospecies—to classify traces based on morphology and assumed behavior, independent of the Linnaean taxonomy of the organisms that produced them. The study intersects with sedimentology and paleoecology to interpret ancient environments; the concept of ichnofacies links suites of trace fossils to depositional settings.

History: The recognition of trace fossils as informative records of paleobiology arose in the 19th century, and ichnology matured with the development of ichnotaxonomy and sedimentological methods in the 20th century. Adolf Seilacher popularized the ichnofacies framework in the mid- to late 20th century, providing a method to interpret ancient habitats from trace fossil assemblages.

Applications: Ichnology informs reconstructions of paleoenvironments, behavior, and paleoecology, and contributes to dating and correlation of rocks. Modern analyses employ field mapping, microscopic examination of sediments, 3D imaging, and quantitative methods to assess trace morphology and distribution.