A trace fossil, also known as an ichnofossil, is a fossil record of biological activity by lifeforms but not the preserved remains of the organism 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. The study of such trace fossils is ichnology and is the work of ichnologists.
Trace fossils are classified in various ways for different purposes. Traces can be classified taxonomically, ethologically, and toponomically, that is, according to their relationship to the surrounding sedimentary layers. Except in the rare cases where the original maker of a trace fossil can be identified with confidence, phylogenetic classification of trace fossils is an unreasonable proposition.
Thalassinoides is an ichnogenus of trace fossil used to refer to "dichotomously or T-branched boxworks, mazes and shafts, unlined and unornamented". Facies of Thalassinoides increased suddenly in abundance at the beginning of the Mesozoic. Such burrows are made by a number of organisms, including the sea anemone Cerianthus, Balanoglossus and fishes, but are most closely associated with decapod crustaceans of the (former) infraorder Thalassinidea.
A zooid or zoöid is a single animal that is part of a colonial animal. This lifestyle has been adopted by animals from separate unrelated taxa. Zooids are multicellular; their structure is similar to that of other solitary animals. The zooids can either be directly connected by tissue or share a common exoskeleton. The colonial organism as a whole is called a zoon, plural zoa.
Paleodictyon is a trace fossil, usually interpreted to be a burrow, which appears in the geologic marine record beginning in the Precambrian/Early Cambrian and in modern ocean environments. Paleodictyon were first described by Giuseppe Meneghini in 1850. The origin of the trace fossil is enigmatic and numerous candidates have been proposed.
Skolithos is a common trace fossil ichnogenus that is, or was originally, an approximately vertical cylindrical burrow with a distinct lining. It was produced globally by a variety of organisms, mostly in shallow marine environments, and appears as linear features in sedimentary rocks.
An ichnofacies is an assemblage of trace fossils that provides an indication of the conditions that their formative organisms inhabited.
Zodiolestes is a genus of mustelids, now extinct, which existed during the Miocene period.
Helminthopsis is the ichnogenus of a type of trace fossil that is found preserved on the bedding planes of fine-grained sedimentary rocks. It is characterized by short, curvilinear, non-branching, parallel-sided, unlined traces on bedding surfaces. It is thought to represent the submarine feeding trails of an invertebrate organism that worked the surface of muddy substrates in search of food. Because Helminthopsis traces never cross over themselves, the ichnogenus is distinguished from similar traces assigned to the Gordia ichnogenus. The similar sounding, but now obsolete, ichnogenus Helminthoida refers to a somewhat similar trace characterized by regular, back-and-forth meanders, whereas Helminthopsis traces are irregular.
The Dwyka Group is one of four geological groups that compose the Karoo Supergroup. It is the lowermost geological group and heralds the commencement of sedimentation of the Karoo Supergroup. Based on stratigraphic position, lithostratigraphic correlation and palynological analyses, these lowermost Karoo strata range between the Late Carboniferous (Pennsylvanian) to Early Permian in age.
Chondrites is a trace fossil ichnogenus, preserved as small branching burrows of the same diameter that superficially resemble the roots of a plant. The origin of these structures is currently unknown. Chondrites is found in marine sediments from the Cambrian period of the Paleozoic onwards. It is especially common in sediments that were deposited in reduced-oxygen environments.
Anthony J. Martin is a paleontologist who has taught at Emory University since the early 1990s. He is best known for his books, An Introduction to the Study of Dinosaurs, Life Traces of the Georgia Coast, Dinosaurs without Bones, and Life Sculpted: Tales of the Animals, Plants, and Fungi that Drill, Break, and Scrape to Shape Earth. He is married to artist Ruth Schowalter.
Nereites is an ichnogenus of trace fossil. Modern tracemakers of incipient Nereites include worm-like organisms, horseshoe crabs and hermit crabs. Traditionally, two models have been proposed for Nereites:
- in the ‘worm model’, Nereites is a feeding burrow produced by wormlike organisms, probing and backfilling laterally
- in the ‘arthropod model’, the characteristic lobes are pressure-release structures made by arthropod legs. According to this interpretation, Nereites is a locomotion trail
Pholad borings are tubular burrows in firm clay and soft rock that have been created by bivalve molluscs in the family Pholadidae. The common names of clams in this family are "pholads", "piddocks", and "angel wings"; the latter because their shells are white, elongated and tend to be shaped like a wing and have sculpture somewhat reminiscent of a wing.
Spreite, meaning leaf-blade in German is a stacked, curved, layered structure that is characteristic of certain trace fossils. They are formed by invertebrate organisms tunneling back and forth through sediment in search of food. The organism moves perpendicularly just enough at the start of each back-and-forth pass so that it avoids reworking a previously tunneled area, thereby ensuring that it only makes feeding passes through fresh, unworked sediment.
The Gabbs Formation is a geologic formation in Nevada. It preserves fossils dating back to the Late Triassic and Early Jurassic periods, and is one of the few formations in the United States known to include the Triassic-Jurassic boundary. In 2007, an exposure of the Gabbs Formation at New York Canyon was proposed a candidate GSSP for the Hettangian stage, the first stage of the Jurassic. However, the New York Canyon section was ultimately not selected as Hettangian GSSP, which instead went to the Kuhjoch section of Austria in 2010.
Frondosity is the property of an organism that normally flourishes with fronds or leaf-like structures.
The Rotzo Formation is a geological formation in Italy, dating to roughly between 192 and 186 million years ago and covering the Pliensbachian stage of the Jurassic Period in the Mesozoic Era. Has been traditionally classified as a Sinemurian-Pliensbachian Formation, but a large and detailed dataset of isotopic 13C and 87Sr/86Sr data, estimated the Rotzo Formation to span only over the Early Pliensbachian, bracketed between the Jamesoni-Davoei biozones, marked in the Loppio Oolitic Limestone–Rotzo Fm contact by a carbon isotope excursion onset similar to the Sinemu-Pliens boundary event, while the other sequences fit with the a warm phase that lasts until the Davoei biozone. The Rotzo Formation represented the Carbonate Platform, being located over the Trento Platform and surrounded by the Massone Oolite, the Fanes Piccola Encrinite, the Lombadian Basin Medolo Group and Belluno Basin Soverzene Formation, and finally towards the south, deep water deposits of the Adriatic Basin. The also Pliensbachian Aganane Formation of Morocco represents a regional equivalent, both in deposition and faunal content.
Orbitolina is an extinct genus of foraminifera belonging to the order Textulariida and family Orbitolinidae. Fossils of this genus are widely found in beds deposited in the Tethys Ocean ranging from Aptian ) to Cenomanian in age. It has been used as a shallow carbonate platform facies marker and as a Cretaceous index fossil.
The Essaouira Agadir basin is a Meso-Cenozoic sedimentary basin located along the Atlantic margin of Morocco at its connection with the Western High Atlas.
