Chondrites

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Chondrites together with an isolated shoulder girdle element of a mesosaurid in a dark claystone of the Mangrullo formation, Unterperm , Uruguay
Historical drawing with a relatively enlarged representation of chondrites from the Posidonia slate (1910).

Chondrites [ kɔnˈdritɛs ] is a genus of fossil traces of life (Ichnogenus) thatoccursin fine-grain, marine sedimentary rocks . The name goes back to Kaspar Maria von Sternberg (1833).

The multi-branched (dendritic) ducts are laid out more or less parallel to the layers, which is why they only occur on layer surfaces in a typical form. The individual corridors are very small, rarely wider than a millimeter. Often they appear en masse and express themselves on fracture and crevice surfaces that are not parallel to the original stratification in an irregular pattern of dots and lines.

The branched, bushy appearance of these trace fossils is reminiscent of plants. In his treatise on the South German Jura from the late 1850s , Friedrich August Quenstedt described the basal layers of Posidonia slate (Lias Epsilon) rich in chondrites as “ seaweed slate ”. The name Algacites , coined by Ernst Friedrich von Schlotheim in the addenda to his "Petrefactenkunde" in 1822, refers at least in part to trace fossils of the Chondrites type, which he also considered to be the remains of aquatic plants. The name Chondrites also goes back to the name of a seaweed genus ( Chondrus , cartilaginous rod ). Also as a result of misinterpretations, the genus name Fucoides , which was coined by Adolphe Brongniart in 1822 based on the name of the seaweed genus Fucus , was used for traces of the Chondrites type, but also for traces that were later due to their relatively strongly different morphology very own genera were assigned. Thus, the names "Chondrites", "Fucoides" and "Algacites" were used in the 19th century for a colorful taxonomic mixture of fossil traces, plants and animals. Still Eberhard Fraas (1910) presented Chondrites to the algae, but expressed already doubts about the general validity of this systematic position. In the years that followed, the view that it was at least partly trace fossils became more and more popular, and the name Chondrites was now only used for this Ichnotaxa.

Which organisms caused these traces has not yet been conclusively clarified. What is clear is that they only occur in marine deposits. In recent, coastal seabeds, traces that match or are very similar to the trace fossil chondrites are produced by sediment- eating bristle worms . Chondrites are proven from the Ordovician onwards. Evidence from the Cambrian is considered uncertain.

See also

The term “chondrites” [ ˈkɔndraɪ̯t͡s ] also refers to special meteorites ( chondrites ) that have nothing to do with this inenological taxon .

literature

  • RG Bromley (1999): Trace Fossils: Biology, Taphonomy, and Applications. Springer, Berlin / Heidelberg. 347 pp. ISBN 978-3-540-62944-3
  • Ulrich Lehmann: Paleontological Dictionary. 4th edition. Enke, Stuttgart 1996, ISBN 3-432-83572-8 , p. 45.

Web links

  • Genus Chondrites Sternberg, 1833 . Data sheet for the trace genus with a comprehensive photo gallery of specimens that have survived in ancient Paleozoic limestones in Estonia (fossiilid.info)
  • Genus Chondrites von Sternberg, 1833 . Datasheet for the trace genus on the website of the IchnoBioGeoScience research group at the University of Kansas (ichnology.ku.edu)

Individual evidence

  1. ↑ Eberhard Fraas: The petrefactor. KG Lutz 'Verlag, Stuttgart 1910, plate 19, figure 3 ( archive.org ).
  2. ↑ Kaspar von Sternberg: Attempt of a geognostic-botanical representation of the flora of the pre-world. Prague, 1833 ( gallica.bnf.fr ), p. 25 .
  3. ^ Friedrich August Quenstedt: The Jura. Verlag der H. Laupp'schen Buchhandlung, Tübingen 1858 ( MDZ reader )
  4. ↑ The species Algacites granulatus established by Schlotheim can be assigned to this trace genus with relative certainty, as it comes from the Posidonia slate of Boll in Württemberg and the illustration and description leave little doubt as to the identity of these traces, see Ernst Friedrich von Schlotheim: Supplements to Petrefactenkunde. Becker'sche Buchhandlung, Gotha 1822, p. 45 f. (GoogleBooks) and Taf. 5, Fig. 1 (GDZ)
  5. ↑ Adolphe Brongniart: Sur la classification et la distribution des végétaux fossiles en general, et sur ceux des terrains des sédiment supérieur en particulier. Memoires de Museum d'Histoire Naturelle. Vol. 8, 1822, pp. 203-240 (introduction and 1st chapter; BHL ), p. 237
  6. ↑ While many of the specimens and taxa initially placed in the genus Fucoides were later recognized as trace fossils, others turned out to be the remains of graptolites , an ancient Paleozoic group of small planktonic animals, see Edith L. Taylor, Thomas N. Taylor, Michael Krings: Paleobotany - The Biology and Evolution of Fossil Plants. 2nd edition. Academic Press / Elsevier 2009, ISBN 978-0-12-373972-8 , p. 122 f.
  7. ↑ For example Fucoides strangulatus from the Bohemian Cretaceous, see Richard Pokorny: Funalichnus , a New Ichnogenus and its Type Ichnospecies Funalichnus strangulatus (Fritsch 1883), Upper Cretaceous of the Bohemian Cretaceous Basin, Czech Republic. Ichnos. Vol. 15, No. 2, 2008, pp. 51–58, doi: 10.1080 / 10420940701192922 (alternative full text access : ResearchGate )
  8. ↑ “ Because of their poor state of preservation, the chondrites are on the whole questionable structure, and it has by no means been established whether they are in fact always of a vegetable nature. For the sake of simplicity, however, we want them here [d. H. with the algae] treat [...]. ”Eberhard Fraas: The petrefactor. KG Lutz 'Verlag, Stuttgart 1910, p. 109 ( archive.org ).
  9. ↑ see e.g. BH Potonié: Textbook of Paleobotany. 2nd edition, revised by W. Gothan. Borntraeger Brothers, Berlin 1921, p. 12 ( archive.org )
  10. ↑ Günther Hertweck, Achim Wehrmann, Gerd Liebezeit: Bioturbation structures of polychaetes in modern shallow marine environments and their analogues to Chondrites group traces. Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 245, 2007, No. 3-4, pp. 382-389, doi : 10.1016 / j.palaeo.2006.09.001
  11. ↑ AH Müller: Textbook of Palaeozoology. Volume II, part 3, Jena 1978.