Tribrachidium
| Tribrachidium heraldicum Temporal range: Ediacaran,
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|---|---|
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| Fossil of Tribrachidium heraldicum | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | Trilobozoa Fedonkin, 1985
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| Family: | Tribrachididae Runnegar, 1992
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| Genus: | Tribrachidium Glaessner, 1959
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| Species: | T. heraldicum
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| Binomial name | |
| Tribrachidium heraldicum Glaessner, 1959
| |
Tribrachidium heraldicum is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. T. heraldicum is the best known member of the extinct group Trilobozoa.
Etymology
The generic name Tribrachidium is derived from combination of the Greek τρία (tria, "three") + Latin brachium ("arm") + diminutive suffix -idium. The specific name T. heraldicum is referring to similarity of the pattern of this fossil with the well-known heraldic triskelion design, such as the coat of arms of the Isle of Man.[1]
Occurrence
Tribrachidium fossils were first discovered in the Ediacara Member of the Rawnslay Quartzite, Flinders Ranges in South Australia.[2][1] This fossil is also known from the Mogilev Formation in the Dniester River Basin, Podolia, Ukraine[3] and from the Verkhovka, Zimnegory an Yorga Formations in the White Sea area of the Arkhangelsk Region, Russia.[4] [5]
Description
T. heraldicum is preserved as negative impressions on the base of sandstone beds. These fossils have a circular, three-lobe form, with straight or trefoil-like edges; they are usually covered by numerous radial branched furrows. The central part of the fossil has three hooked ridges ("arms"). The lobes are twisted into weak spirals.[6]
The diameter of specimens range from 3 millimeteres to 5 centimeters.
Reconstruction and affinity
Tribrachidium was originally described by Martin Glaessner as a problematic organism, one that is excluded from all known major groups of animals by its three-radial symmetry. However, Tribrachidium's superficial resemblance to edrioasteroid echinoderms was well known to researchers and discussed.[1][2] Later, Glaessner rejected any putative affinities of this animal with any known phyla, leaving the status of its taxonomy uncertain.[7] Originally, the various structures on the poorly preserved Australian specimens were interpreted as tentacles, peculiar arms and mouth,[2] but later this interpretation was rejected.
With the discovery of the closely related Albumares and Anfesta, along with the discoveries of much better-preserved Russian specimens, Mikhail Fedonkin proposed for these animals the new taxon, Trilobozoa – extinct group of the tri-radially symmetrical coelenterate-grade animals.[8][9] Originally, Trilobozoa was erected as a separate class in the phylum Coelenterata, but since Coelenterata was divided into separate phyla Cnidaria and Ctenophora, the Trilobozoa have been transferred to the rank of phylum.[10]
M. Fedonkin has shown that the Tribrachidium fossil is an imprint of the upper side of the animal's body, with some elements of its external and internal anatomy. The radial furrows on the fossil are radial grooves on the surface of the alive animal, while the three hooked ridges in central part of the fossil are imprints of cavities within the body.[8] Tribrachidium was a soft-bodied benthic organism that temporarily attached (but did not accrete) to the substrate of its habitat (microbial mats).[6]
See also
References
- ^ a b c Glaessner, M.F. (1959). "The geology and Late Precambrian fauna of the Ediacara fossil reserve" (PDF). Records of the South Australian Museum. 13 (3): 369–401.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ a b c Glaessner, M.F. (1966). "The late Precambrian fossils from Ediacara, South Australia" (PDF). Palaeontology. 9 (4): 599.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Fedonkin, M. A. (1983). "Non-skeletal fauna of Podoloia, Dniester River valley". In Velikanov, V. A.; Asse]eva, E. A. and Fedonkin, M. A. (ed.). The Vendian of the Ukraine (in Russian). Kiev: Naukova Dumka. pp. 128–139.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ Fedonkin M.A. (1978). "New locality of non-skeletal Metazoa in the Vendian of Whinter Coast". Doklady Akademii Nauk SSSR (in Russian). 239 (6): 1423–1426.
- ^ Fedonkin M. A., Gehling J. G., Grey K., Narbonne G. M., and Vickers-Rich P. (2007). The Rise of Animals. Evolution and Diversification of the Kingdom Animalia. Johns Hopkins University Press. p. 326. ISBN 978-0-8018-8679-9.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b Ivantsov, A. Yu.; Leonov M. V. (2009). The imprints of Vendian animals - unique paleontological objects of the Arkhangelsk region (in Russian). Arkhangelsk. p. 91. ISBN 978-5-903625-04-8.
{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: multiple names: authors list (link) - ^ Glaessner, M. F. (1979). "Precambrian". In Robison, R. A.; Teichen, C. (ed.). Treatise on invertebrate paleontology, Part A. Boulder, Colorado, Geological Society of America: University of Kansas Press. pp. 79–118.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ a b Fedonkin, M. A. (1985). "Systematic Description of Vendian Metazoa". In Sokolov, B. S.; Iwanowski, A. B. (ed.). Vendian System: Historical–Geological and Paleontological Foundation, Vol. 1: Paleontology (in Russian). Moscow: Nauka. pp. 70–106.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ Fedonkin, M. A. (1990). "Precambrian Metazoans". In Briggs D.; Crowther P. (ed.). Palaeobiology: A Synthesis (PDF). Blackwell. pp. 17–24.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ Runnegar, B. N.; Fedonkin, M. A (1992). "Proterozoic Metazoan Body Fossils". In Schopf, J. W.; Klein, C. (ed.). The Proterozoic Biosphere: A Multidisciplinary Study. Cambridge University Press. p. 373.
{{cite book}}: CS1 maint: multiple names: authors list (link)
External links
- [1] Palaeos dendrogram
- Ediacara Assemblage University of Bristol
- Anatomical Information Content in the Ediacaran Fossils and Their Possible Zoological Affinities, Jerry Dzik, Instytut Paleobiologii PAN, Twarda 51/55, 00-818 Warszawa, Poland
