Palichnology

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Footprints of Chirotherium (here, the imprint of a rear extremity ). This trace of movement caused by early archosaurs was discovered in 1833, described in 1834 and named in 1835. It is the first scientifically described trace of a land vertebrate.

The trace fossil (more rarely Paläoichnologie ; . Greek palaios "old" Ichnos "footprint" logos "doctrine") deals as a branch of paleontology with the fossil traces of life of the Earth's history. Such trace fossils can, such as B. footprints (footprints) and tracks shape, a former sediment surface or penetrate as grave courses and residential buildings, formerly near-surface horizons depth.

Trace fossils are also called Ichnofossils or Ichnia ( Sing. Ichnium ). The term Ichnologie (trace science) was first used by William Buckland (1784-1856) around 1830. The palichnology is contrasted with the neoichnology , which deals with recent traces of life.

The previously oldest traces were on a 565 million years old rocks at Mistaken Point of Avalon -Halbinsel in Newfoundland ( Canada discovered). The total of 70 tracks, each 13 mm wide and between 5 and 17 cm long, come from animals of the Ediacara fauna with a presumably rounded foot disk, as found in today's sea ​​anemones . Probably the oldest tracks of a bilaterally symmetrical animal come from 551 to 541 million year old Ediacara find layers in the south of the People's Republic of China .

Classification of fossil traces

Trace taxonomy (egotaxonomy)

Asteriacites is a very well-known example of a quiet trail . Here of brittle stars caused A. lumbricalis as a raised relief on the bottom layer of Hangendplatte .
The rest trail of a trilobite (trace genus Rusophycus ) shows the outline of its producer ( Ordovician of Ohio, scale = 10 mm)

Since trace fossils are not the remains of animal bodies and since different groups of organisms can morphologically produce very similar traces and, conversely, one and the same species of animal can leave different traces, palichnology classifies traces as form taxa , regardless of the zoological taxonomy of fossil organisms in this case, called Ichnotaxa . A distinction is made primarily between trace genera (Ichnogenera) and trace types (Ichnospezies), which are named according to Linnaeus' nomenclature . The basis for classifying traces in the same type of trace and subdividing them into different types of traces are common morphological features that can be traced back to the more or less identical behavior of the trace producer or morphological differences that have come about due to slight deviations in the behavior of the trace producer. This concerns the general shape of the track (mostly genus-specific), especially in the case of corridors in the sediment, also the wall structure, the spatial position and special features of the sediment filling (e.g. so-called stuffing structure ). Differences specific to trace species or subspecies can also be caused by differences in the physique of the producers (so-called "fingerprinting"), which does not necessarily have to be due to the fact that the producers belonged to different biological species, but also, for example, fundamentally similar behavior at different stages in the Individual development (ontogenesis) can reflect one and the same type of producer.

In the case of terrestrial vertebrate tracks, in contrast to the tracks of many marine invertebrates, there is generally a relatively close connection between the morphology of the track, i.e. H. the imprint of the extremity, and the morphology of the extremity of the producer and thus his taxonomic position. Therefore, in this trace group, a distinction is often made between higher taxa, such as trace families and trace orders, whose names are based on the body fossil taxonomy. Sometimes terrestrial vertebrate species are even included directly in the zoological system, which is rejected by many paleichnologists.

A very well-known and at the same time the oldest example of an Ichnotaxon in terms of scientific history is Chirotherium barthii ("Barth's hand animal") from the Triassic . Friedrich Sickler published a scientific description of this trajectory in 1834 on the basis of tracks on a sandstone slab from the middle red sandstone , which had been found in southern Thuringia near Hildburghausen , and Johann Jakob Kaup gave it the name a year later. However, there was a long-standing scientific controversy about who was responsible for the traces. Today representatives of the early Archosaurs are considered to be producers of Chirotherium .

Ethological classification

The ethological classification differentiates trace fossils roughly according to the behavior of the producing organism that led to the creation of the corresponding trace. The various ethological classes of trace fossils are listed below. The first five (traces of rest to traces of living) come from the traditional ethological classification according to Adolf Seilacher (1953). The other classes were set up in more recent work. It should be noted that there are traces that represent transitional forms between two classes, which can be assigned to several classes or for which it is not exactly clear which ethological type of trace they are to be assigned to (e.g. Lumbricaria ).

With regard to trace taxonomy, the general rule is that traces from different ethological classes are usually not in the same trace genus, while traces that are assigned to the same trace type or genus usually also belong to the same ethological class.

Resting traces (Cubichnia)

If an actively mobile (vagile) marine animal burrows itself a little bit in the sediment and then leaves this place again in the same way, it causes sediment structures, which are known as traces of rest (Cubichnia) and the body contours of the producing animal z. Some of them are surprisingly similar. This happens u. a. to catch or eat buried prey (e.g. with starfish ) or to protect them from predators (e.g. mussels or some shrimp ). The term resting track refers to the fact that it comes about when its creator remains largely stationary (“at rest”), i.e. does not move from A to B (cf. movement tracks ). Typical examples are Rusophycus , Lockeia and Asteriacites .

Movement or crawl marks (Repichnia)

The approximately 330 million year old traces of movement of the "sea scorpion" Hibbertopterus are the largest known traces of movement of an arthropod on land . The slightly curved track runs from left to right (above the hammer).
Schematic animation for the interpretation of the trace fossils from the deeper Devonian of the Heiligkreuzgebirge as a step seal of a land vertebrate
Replica of Eubrontes (tracked bipeder , three-toed dinosaur ) from the Spanish province of La Rioja
Kouphichnium lithographicum , the movement track of a horseshoe crab with producer Mesolimulus in Solnhofen ( Oberjura )

Traces of movement are caused by organisms that crawl, stride, swim close to the ground or similar on the sediment surface. These tracks usually run in straight to slightly curved lines and with roughly parallel side edges. Examples of this are Cruziana , Diplichnites , Undichnus , Kouphichnium as well as all tracks of land vertebrates (Tetrapoda) (for the latter see also →  Tracking sandstone ).

Grazing tracks (Pascichnia)

Vagile sediment eater create pasture structures by moving on or near the surface parallel layers in a sediment and thereby “graze” on enriched detritus or other food sources, whereby they usually leave a closely meandering pattern. Typical representatives are Helminthopsis , Nereites and Phycosiphon . Also Cruziana and Rusophycus are sometimes classified here.

Seizing marks (Fodinichnia)

Domichnion or Fodinichnion: thalassinoides structures caused by crustaceans . Middle Jurassic, Machtesch Katan , South Israel.

In contrast to the Pascichnia , Fodinichnia are not layer-parallel and are also created in lower levels of the sea floor by sediment eater . Fodinichnia are usually composed of one or more vertical passages, which are connected to the sediment surface and serve to supply fresh water, as well as one or more approximately horizontal feeding passages. This structure is used by the producer for both living and eating. Examples are Thalassinoides suevicus , Dactyloidites ottoi , Rhizocorallium irregulare , Palaeophycus , Planolites and also some forms of Zoophycos .

Residential traces (Domichnia)

Praedichnion: Fossil leaf of the snowball species Viburnum lesquereuxii with insect damage . From the Cretaceous Dakota Formation in Ellsworth County (USA).

A building primarily designed for permanent living is called a residential track (Domichnion). Such structures are built both in what is known as a soft substrate , usually the unconsolidated sediment of a sea or lake bed, and in what is known as a hard substrate , usually hard rock (mostly limestone, e.g. on rocky coasts) or the exoskeletons of marine animals. Traces of living are buildings in which, for example, stationary ( sessile ) suspension eaters, less mobile detritus eaters or ambulance hunters spend most of their lives. Typical representatives of this type of trace in (former) soft substrates are e.g. B. Skolithos , Ophiomorpha and Arenicolites . Domichnia in hard substrates, e.g. B. Trypanites , and - depending on the definition - also in wood (e.g. Teredolites ) fall under the generic term bioerosion . Bodies of terrestrial vertebrates, including the spiral-shaped daemonelix created by the tertiary rodent Palaeocastor , are relatively rare .

Traps and Cultivation Traces (Agrichnia)

Agrichnia are fossil structures that served organisms as traps to obtain food, such as z. B. adopted for Spirorhaphe and Cosmorhaphe , or as a "greenhouse" for the cultivation of microorganisms such. B. assumed for Paleodictyon and Helicolithes . Some of these structures may have been created especially in deep sediment layers with a euxinic milieu , as their producers lived in symbiosis with sulfur-oxidizing bacteria , as is the case e.g. B. is suspected to be the cause of chondrites .

Traces of Robbery (Praedichnia)

Praedichnia are structures caused by predatory activity, such as oichnus , which are boreholes that were taken by e.g. B. Moon snails (Naticidae) were produced in mussel shells, or Phagophytichnus , feeding traces in leaves. Other examples are external and internal skeletons broken and bitten by robbers. Praedichnia on shellfish and - in the broadest sense - also feeding marks on plants fall under the umbrella term bioerosion.

Compensating tracks (Equilibrichnia)

When organisms have to change their position in the sediment in order to adapt to a change in the sediment surface, they create compensation tracks. This happens when the sediment surface is slowly removed or piled up.

Aligned tracks (Fugichnia)

In contrast to the Equilibrichnia , the original sediment structure was disturbed by the rapid grave activity of the producer with this type of trace , which is often expressed in sickle-shaped, finely laminated structures. The escape is triggered by a rapid accumulation or erosion of the sediment in which the producer lives. A predator digging for the fugichnium producer can also be the cause.

Traces created over the substrate (Aedificichnia)

These include trace fossils that were created on and / or above the substrate and are created from sediment particles cemented together, e.g. B. Wasp nests made of mud, anthills , termite burrows , tubes of caddis fly larvae and "sand organs" that are built by tube worms .

Breeding structures (Calichnia)

Calichnia are structures created for reproductive purposes and for raising young animals and larvae . The boundaries to the Fodinichnia (e.g. insect larvae in and on leaves) and the Aedificichnia (e.g. hill-like dinosaur nests, caddis-fly larvae tubes) are often blurred .

Anchoring tracks (Fixichnia)

Sessile marine animals leave characteristic etched scars on the surface of carbonate hard substrates, which originate from the fact that the cause was anchored in the appropriate place. A distinction is made between two types of Fixichnia: traces that go back to anchoring by organs of the soft body (e.g. the byssus threads of mussels) and traces that were created because the exoskeleton of the causer was cemented to the ground. Examples of the former are Podichnus and Centrichnus eccentricus , examples of the latter Leptichnus and Centrichnus concentricus . Fixichnia belong to the bio-erosion structures.

Trace fossil associations and degree of bioturbation

The totality of all traces of a certain space or rock is called Ichnozoenosis (fossil also paleoichnozoenosis). Often trace societies show a horizontal sequence within the sediment due to the different ways of life and habits of its producers. H. a story building. A horizontal sequence of different fossil traces in the rock can, however, also represent successions , i.e. a chronological sequence of different trace fossil associations.

Trace fossil communities, which have been typical for a certain deposit area over and over again in the course of the earth's history, are referred to as Ichno facies . A characteristic trace socialization can therefore be important for the interpretation of the genesis of a sedimentary rock . Statements on environmental factors such as oxygen content, salinity and sedimentation rate in a marine deposit area can be derived from the analysis of trace fossil associations.

The destruction of original sedimentary features by burrowing organisms is known as bioturbation . So z. B. a previously stratified sand can be homogenized by bioturbation, so that the stratification is extinguished. The degree of bioturbation describes the percentage of bioturbated sediment in a layer.

Biostratigraphy

In contrast to body fossils , most trace fossils have limited potential for biostratigraphic applications. Ichnia usually do not preserve the anatomically clear characteristics of the producer, since the morphology of traces is usually determined by the ethology and not by the anatomy of an animal. In this way, many traces of invertebrates can be traced back to different producers. Typical trace fossils without biostratigraphic significance are Palaeophycus or Planolites , which can be found in almost all facies areas and stratigraphic units. More likely culprits are worms and arthropods (arthropods).

Biostratigraphically significant trace fossil groups

Cruziana - Rusophycus

Rusophycus polonicus , a trace fossil for the Upper Cambrian ( Furongian ).

These traces, which are mainly found in marine sandstones of the Paleozoic Era , are mainly attributed to the activity of trilobites . The Cruziana -Ichnostratigraphie , widely recognized in specialist circles, was largely developed by Adolf Seilacher . Especially in shallow marine siliciclastics with few body fossils , the occurrence of certain Cruziana chnospecies can provide valuable clues for the relative age of the rock. In contrast to most of the traces caused by invertebrates , in Cruziana and Rusophycus there is a close connection between the anatomy of the exoskeleton , especially the " legs ", of the producer and the special morphology of the trace fossil ("fingerprinting"). Thus the evolution within the group of organisms of the trace producers is reflected in the trace fossil record.

Tetrapod tracks

In silicicoplastics in continental sedimentation areas, footsteps from terrestrial vertebrates (Tetrapoda) are often the only fossil evidence of primeval vertebrates. Due to the fact that the shape of the traces of life is directly related to the anatomy of the producer, evolutionary trends can be recognized and used for temporal classification. A very well-known example of tetrapod traces are the tracks from the chiroteria sandstone of the Solling series (middle red sandstone ). The oldest traces of land vertebrates, interpreted as such, originated in a mudflat . They were discovered in a quarry in the Heiligkreuz Mountains (southern Poland) and dated to an age of 395 million years (border area Lower and Central Devon ). The oldest traces of land vertebrates from the inland are 318 million years old and originated 500 km from the coast of the supercontinent Pangea .

Treptichnus pedum

Although this trace fossil shows no significant change due to the geological time scale and only documents a weakly specialized feeding behavior of invertebrates, great importance is attached to this structure. Treptichnus pedum is the key fossil for the Precambrian / Cambrian border and documents what is probably the most significant change in the history of life. At the base of the Phanerozoic , a process that is commonly known as the Cambrian Explosion took place : almost all the blueprints for today's groups of organisms were created within a geologically short period of time . Since body fossils are seldom and difficult to correlate stratigraphically, especially in the lowest Cambrian, the FAD (English: F irst A ppearance D atum , German: first appearance) of Treptichnus pedum was used to define this crucial geological boundary , as this structure represents a specialized feeding behavior can be traced back to the activity of complex multicellular animals (Metazoa). Nevertheless, the suitability as a guide fossil is controversial. It is argued that Treptichnus pedum merely represents grazing on the underside of algae mats (“undermatmining”), a feeding technique that was also used by lower organisms and that was already widespread in the Upper Precambrian. In addition, Treptichnus pedum , like most trace fossils, is strongly facies-dependent , a property that is undesirable in reference fossils.

Fossil prehuman and human tracks

A hominine track described in 2016 at Laetoli
Site of the 800,000 year old footprints near Happisburgh
Close-up of the footprints
(with the lens cover of a camera as a size comparison)

A special form of tetrapod tracks are those that were created by the ancestors of anatomically modern humans ( Homo sapiens ) who were already walking upright (bipedes) . The oldest of these tracks (<1  mya ) occur exclusively in Africa. In an on Crete discovered 5.7 mya old footprint is unclear due to her advanced age and their geographical position, whether a "real" pre-human (that is an early representative of the tribe Hominini ) is to be allocated, or a line of development which converges a developed human-like foot anatomy.

At Laetoli in Tanzania in 1978 corresponding tracks were discovered dated to about 3.6 mya, and probably of Australopithecus afarensis were generated. They are considered to be the oldest trace fossils made by hominini. As the renowned science magazine Nature reported in April 2008, these traces are threatened with decay.

At Ileret , east of Lake Turkana in Kenya , footprints of Homo erectus from 1.51 to 1.53 million years ago were uncovered. The tracks show that the structure of the feet essentially coincided with that of modern humans and that the upright gait of H. erectus must have already closely resembled that of modern humans. Some footprints from the Koobi Fora site on the northeast coast of Lake Turkana are also around 1.5 million years old .

The oldest footprints of "prehistoric men" in Europe were discovered in the eastern English county of Norfolk . Researchers working with Chris Stringer uncovered them in May 2013 near Happisburgh , dated them to an age of around 800,000 years and, based on this age, interpreted them as traces of Homo antecessor , as this species is the only one described in Europe from this period.

Three 385,000 to 325,000 year old tracks that were discovered in southern Italy ( Roccamonfina ) together with other mammalian traces in pyroclastic sediments probably come from Homo heidelbergensis . The tracks were created by individuals walking down the slope. One of the tracks is Z-shaped, which is probably due to the fact that its producer ran partly parallel to the slope in order to be able to cope with the descent more easily. The lower part of the second track shows clear signs that its producer must have slipped. Handprints next to the track are interpreted as an attempt on the part of the producer to maintain balance by propping them up.

Since 2008, footprints of early, anatomically modern humans that are around 120,000 years old and which were impressed into fresh volcanic ash on the shores of Lake Natron in Tanzania have been analyzed . A total of 350 imprints on 150 square meters have been verified. They come from more than 30 individuals (men, women and children) who were probably traveling in two groups.

117,000 years old are footprints in South Africa , bordering the located southeast of the Saldanha Bay then Langebaan Lagoon , were discovered and - also the early - like the same old traces of Nahoon Homo sapiens Act. The Langebaan tracks discovered by the geologist David Roberts were pressed into the rain-moistened sand on the slope of a dune and a short time later they were blown with sand. As a result of subsequent erosion, the layer with the track is now back on the earth's surface.

Three footprints of a Neanderthal man in a carbonate , limestone-like cave sediment ( moon milk ), which were discovered in 1974 in the Vârtop cave in the Bihor Mountains ( Romania ), have been dated to an age of 97,000 years . A group of more than 250 footprints of 10 to 13 mostly very young and adolescent Neanderthals in a dune area of Le Rozel in the French department of Manche in the Normandy region is around 70,000 ± 10,000 years old .

The oldest footprints of anatomically modern humans in Europe were discovered in 1965 in the Ciur-Izbuc Cave in the western Romanian Carpathian Mountains and, based on accompanying finds of cave bear bones and tracks, initially dated to a minimum age of 10,000 to 15,000 years. However, a new dating of the meanwhile partially destroyed traces using the radiocarbon method , which was published in 2014, assigned them a significantly older age of up to 36,000 years.

literature

  • RG Bromley: Trace Fossils: Biology, Taphonomy, and Applications. Springer, Berlin / Heidelberg 1999, ISBN 978-3-540-62944-3 , 347 pp.
  • W. Miller, ed .: Trace Fossils: Concepts Problems Prospects. Elsevier, 2006, ISBN 978-0-444-52949-7 , 632 pp.
  • A. Seilacher: Trace Fossils Analysis. Springer-Verlag, Berlin / Heidelberg 2007, ISBN 978-3-540-47225-4 , 226 pp.
  • AA Ekdale et al .: Ichnology: trace fossils in sedimentology and stratigraphy. Society of Economic Paleontologists and Mineralogists, Short Course Notes, No. 15. Tulsa, Oklahoma 1984, ISBN 978-0-918985-42-2 . 317 pp.

Web links

Commons : Category “Trace Fossils”  - album with pictures, videos and audio files

Individual evidence

  1. ↑ Hartmut Haubold dinosaur tracks. Die Neue Brehm-Bücherei Vol. 479. - A. Ziemsen Verlag, Wittenberg Lutherstadt, 1984. ISBN 3-89432-401-5 .
  2. ↑ a b c Ulrich Lehmann : Paleontological dictionary . 4th edition. Ferdinand Enke Verlag, Stuttgart 1996, ISBN 3-432-83573-6 .
  3. ↑ Alexander G. Liu, Duncan McIlroy, Martin D. Brasier: First evidence for locomotion in the Ediacara biota from the 565 Ma Mistaken Point Formation, Newfoundland. In: Geology. Volume 38, No. 2, 2010, pp. 123-126, doi: 10.1130 / G30368.1 .
  4. ↑ Zhe Chen, Xiang Chen, Chuanming Zhou, Xunlai Yuan, Shuhai Xiao: Late Ediacaran trackways produced by bilaterian animals with paired appendages. In: Science Advances. Volume 4, No. 6, eaao6691, doi: 10.1126 / sciadv.aao6691
  5. ^ Andreas E. Richter : Handbook of the fossil collector. P. 405. Weltbild Verlag, Augsburg, 1999. ISBN 3-440-05004-1 .
  6. ^ Bromley: Trace Fossils. 1999 (see literature ), p. 173
  7. ↑ Martin Lockley: In the footsteps of the dinosaurs. Dinosaur tracks - an expedition into the past. Birkhäuser Verlag, Basel [u. a.] 1993, ISBN 978-3-7643-2774-3 , p. 7.
  8. ↑ a b c J. M. de Gibert, R. Domènech, J. Martinell: An ethological framework for animal bioerosion trace fossils upon mineral substrates with proposal of a new class, fixichnia. Lethaia, Vol. 37, 2004, pp. 429-437, doi : 10.1080 / 00241160410002144 .
  9. ^ Adolf Seilacher: Cruziana stratigraphy of "non-fossiliferous" Paleozoic sandstones. In: TP Crimes, JC Harper (Eds.): Trace Fossils. In: Geological Journal , Volume 3, 1970, pp. 447-476. ISBN 0-902354-09-4 .
  10. ↑ Grzegorz Niedźwiedzki et al .: Tetrapod trackways from the early Middle Devonian period of Poland. In: Nature , Volume 463, 2010, pp. 43-48, doi : 10.1038 / nature08623 .
  11. ^ Howard J. Falcon-Lang et al .: Diverse tetrapod trackways in the Lower Pennsylvanian Tynemouth Creek Formation, near St. Martins, southern New Brunswick, Canada. In: Palaeogeography, Palaeoclimatology, Palaeoecology , Vol. 296, No. 1-2, 2010, pp. 1-13. doi : 10.1016 / j.palaeo.2010.06.020 .
  12. ↑ Gerard D. Gierliński, Grzegorz Niedźwiedzki, Martin Lockley, Athanassios Athanassiou, Charalampos Fassoulas, Zofia Dubicka, Andrzej Boczarowski, Matthew R. Bennett, Per Erik Ahlberg: Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete? In: Proceedings of the Geologists' Association. Volume 128, No. 5-6, 2017, pp. 697-710, doi: 10.1016 / j.pgeola.2017.07.006
  13. ^ Mary D. Leakey , RL Hay: Pliocene footprints in the Laetoli beds at Laetoli, northern Tanzania. In: Nature . Volume 278, 1979, pp. 317-323, doi : 10.1038 / 278317a0 .
  14. ↑ Anonymous: Tanzania takes steps to save ancient human prints. In: Nature. Volume 452, 2008, p. 677, doi: 10.1038 / 452677c .
  15. ^ "The Ileret prints show that by 1.5 Ma, hominins had evolved an essentially modern human foot function and style of bipedal locomotion." Matthew R. Bennett, John WK Harris, Brian G. Richmond, David R. Braun, Emma Mbua, Purity Kiura, Daniel Olago, Mzalendo Kibunjia, Christine Omuombo, Anna K. Behrensmeyer, David Huddart, Silvia Gonzalez: Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya. In: Science . Volume 323, No. 5918, 2009, pp. 1197-1201, doi: 10.1126 / science.1168132 .
  16. ↑ Anna K. Behrensmeyer, Léo F. Laporte: Footprints of a Pleistocene hominid in northern Kenya. In: Nature. Volume 289, 1981, pp. 167-169, doi: 10.1038 / 289167a0
  17. ↑ Nick Ashton et al .: Hominin Footprints from Early Pleistocene Deposits at Happisburgh, UK. In: PLoS ONE. Volume 9, No. 2, e88329, doi: 10.1371 / journal.pone.0088329
  18. ↑ Ashleigh LA Wiseman, Chris B. Stringer, Nick Ashton et al .: The morphological affinity of the Early Pleistocene footprints from Happisburgh, England, with other footprints of Pliocene, Pleistocene, and Holocene age. In: Journal of Human Evolution. Volume 144, 2020, 102776, doi: 10.1016 / j.jhevol.2020.102776 .
  19. ↑ Paolo Mietto, Marco Avanzini, Giuseppe Rolandi: Human footprints in Pleistocene volcanic ash. In: Nature. Volume 422, 2003, p. 133, doi: 10.1038 / 422133a
  20. ^ Ann Gibbons: Ancient Footprints Tell Tales of Travel. In: Science. Volume 332, No. 6029, pp. 534-535, doi: 10.1126 / science.332.6029.534-b .
  21. ↑ David Roberts, Lee Berger : Last interglacial (c. 117 kyr) human footprints from South Africa. In: South African Journal of Science. Volume 93, 1997, pp. 349-350.
  22. ↑ nationalgeographic.com of August 14, 1997: Footprints Found in South Africa Come From Dawn of Modern Humans.
    Rick Gore: Tracking the First of Our Kind. In: National Geographic . September 1997, pp. 92-99.
  23. ^ David L. Roberts, Last Interglacial Hominid and Associated Vertebrate Fossil Trackways in Coastal Eolianites, South Africa. In: Ichnos: An International Journal for Plant and Animal Traces. Volume 15, No. 3-4, 2008, pp. 190-207, doi: 10.1080 / 10420940802470482
  24. ↑ Bogdan P. Onac, Iosif Viehmann, Joyce Lundberg, Stein-Erik Lauritzen, Chris Stringer, Vasile Popiţă: U – Th ages constraining the Neanderthal footprint at Vârtop Cave, Romania. In: Quaternary Science Reviews. Vol. 24, No. 10-11, 2005, pp. 1151-1157, doi: 10.1016 / j.quascirev.2004.12.001
  25. ^ Norbert Mercier et al .: Dating the palaeolithic footprints of 'Le Rozel' (Normandy, France). In: Quaternary Geochronology. Volume 49, 2019, pp. 271-277, doi: 10.1016 / j.quageo.2017.12.005
  26. ↑ Jérémy Duveau, Gilles Berillon, Christine Verna, Gilles Laisné and Dominique Cliquet: The composition of a Neandertal social group revealed by the hominin footprints at Le Rozel (Normandy, France). In: PNAS . Online advance publication of September 9, 2019, doi: 10.1073 / pnas.1901789116
  27. ↑ David Webb, Marius Robu, Oana Moldovan, Silviu Constantin, Bogdan Tomus, Ionel Neag: Ancient human footprints in Ciur-Izbuc Cave, Romania. In: American Journal of Physical Anthropology. Advance online publication of July 7, 2014, doi: 10.1002 / ajpa.22561