Rangea

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Rangea
Rangea longa fossil from Newfoundland (bottom right), kept in the Paleontological Museum in Tübingen

Rangea longa fossil from Newfoundland (bottom right), kept in the Paleontological Museum in Tübingen

Temporal occurrence
558 to 549 million years
Locations
Systematics
Empire : Animals (Animalia)
Multicellular animals (Metazoa)
Trunk : Vendozoa
Sub-stem : Rangeomorpha
incertae sedis
Genre : Rangea
Scientific name
Rangea
Gürich , 1929

Rangea is an extinct genus from the geological age of the Ediacarium . This removes living beings resembling a fern leaf with six symmetry, the systematic allocation of which is controversially discussed, belongs to the so-called Ediacara fauna . The fossil was the first finding of a large and complex organism from the Precambrian .

Etymology and first description

Rangea schneiderhoehni was named after its discoverers, Paul Range and Hans Schneiderhöhn . The first find dates from 1908 and comes from the Nama group of Namibia . The fossil was thenscientifically describedin 1929 and again in 1930 by Georg Gürich . Other important arrangements were made by Rudolf Richter (1955), Hans Dieter Pflug (1970), GJB Germs (1972 and 1973), Martin Glaessner (1979), RJF Jenkins (1985) and J. Dzik (2002).

Taxonomy

The sea feather Virgularia sp.

The systematic classification of Rangea is controversial in science, but mostly Rangea is assigned to the realm of multicellular animals ( Metazoa ). Similarities with today's sea ​​feathers are striking, although there is probably no direct relationship. Dzik (2002) thinks he can recognize similarities with the rib jellyfish (Ctenophora). According to Seilacher and colleagues (2003), Rangea belongs to the extinct tribe of the vendobionts , which are interpreted as gigantic single-celled organisms ( eukaryotes ) and are classified as protozoa . Jack Sepkoski (2002) classifies Rangea as belonging to the sub-tribe Rangeomorpha - sessile organisms that were characterized by a fractal-like growth - and also regards Rangea as a type fossil of this group.

In addition to the type fossil Rangea schneiderhoehni , which is identical to Rangea brevior Gürich 1933 , there are four other subtaxa, which are all synonyms of other taxa:

  • Rangea arborea Glaessner and Wade 1966 : is identical to Charniodiscus arboreus
  • Rangea grandis Glaessner and Wade 1966 or Glassnerina grandis : is identical to Charnia masoni
  • Rangea longa Glaessner and Wade 1966 : is identical to Charniodiscus longus
  • Rangea sibirica Sokolov 1972 or Charnia sibirica : is also identical to Charnia masoni .

Rangea arborea , Rangea grandis and Rangea longa were discovered in 1966 by Martin Glaessner and Mary Wade in the Flinders Ranges in South Australia. Rangea sibirica is native to the Olenyuk region in eastern Siberia .

Similar forms are Swartpuntia with quadruple symmetry, Bomakellia , Charnia , Charniodiscus , Paracharnia and the enigmatic taxon Thaumaptilon , which supposedly survived into the Cambrian . The taxa Avalofractus , Beothukis , Fractofusus , Frondophyllas , Hapsidophyllas , Khatyspytia , Trepassia , Vauzutsinia and Vinlandia are also in taxonomic proximity .

features

The puzzling animal impresses with its similarity to the current Pennatulacea ( octocorals , sea feathers) belonging to the cnidarians (Cnidaria ). Rangea was elongated , but his stature was still rather small to medium-sized (height 5 to 15 centimeters).

Rangea had a hexaradial, bulbous anchorage on the ground, which merged into a round axis stem, which extended over the rest of the height of the animal. Above the anchorage, there followed six radially, at an angle of 60 ° around the central axis, arranged flags (or fronds or petalodium, English vanes or petaloids ) of elongated, semi-oval shape. As with fern fronds, these flags consisted of branching ribs (or branches) that were organized in a self-similar manner ( fractal ) up to at least the third, if not the fourth dimension .

The anchorage was filled with sediment, but its concentration became less and less towards the stem. The cylindrical and conical stem was free of sediments and completely hollow inside. A mucous protective covering covered the interior of the organism. Sack-like organelles branched off from a central duct, but the rest of the internal structure is not further known. The outer skin was smooth and soft.

Vickers-Rich and colleagues (2013) reinterpreted Rangea in which a central stem is no longer present. Instead of the stalk, the animal only has a central cavity, which replaces the originally assumed stalk. The six leaf-like flags (petalodia) are bordered at their edge by "tubes" that extend from the base of the central cavity, pull up to the top of the animal and then converge there. The discovery of a bulbous anchorage also goes back to Vickers-Rich and colleagues; it is still missing from all previous interpretations. According to them, the anchorage also has six hexagonally arranged bulges running along it, over which the individual petalodies are based.

Occurrence

The site of the Farm Aar in Namibia

The type fossil Rangea schneiderhoehni was found in the Dabis formation ( Kanies member and Kliphoek member ), in the Kuibis formation (Kuibis quartzite) and in the Nudaus formation ( Niederhagen member ) at Farm Aar in Namibia. The deposits date from around 548 million years BP towards the end of the Ediacarian. Other Rangea fossils were discovered in the Yorga Formation near Arkhangelsk in Russia, Mongolia, and Australia . These finds are somewhat older and date between 558 and 555 million years BP. A more recent find from 2013 comes from China from the Dengying Formation southeast of Zigui ( Yangtze Kraton ), which is dated to 551 to 541 million years BP.

Way of life

Rangea was evidently a stuck benthic organism and lived upright on the ocean floor. However, all previously known fossils had been torn from their original location and are now found in storm deposits ( tempestites ). Some authors also advocate an endobenthic way of life in the sediment of the sea floor. There are no signs of a mouth opening in Rangea , so it is assumed that the animal was osmotically nourished. The high surface-to-volume ratio of the individual fronds (maximizing the surface), comparable to modern osmotrophic bacteria, seems to support this assumption. However, other authors prefer a filtering way of life.

Individual evidence

  1. ↑ a b Chen, Zhe et al: New Ediacara fossils preserved in marine limestone and their ecological implications . In: Scientific Reports . tape 4 , 2014, p. 4180 , doi : 10.1038 / srep04180 .
  2. ^ Gürich, G .: The oldest fossils in South Africa . In: Journal of practical geology with special consideration of the geology of deposits . tape 37 , 1929, pp. 85 .
  3. ^ Gürich, Georg: About the Kuibis quartzite in South West Africa . In: Journal of the German Geological Society . v.82, 1930, p. 637 .
  4. ↑ a b Dzik, J .: Possible ctenophoran affinities of the precambrian "sea-pen" Rangea . In: Journal of Morphology . tape 252 (3) , 2002, pp. 315-334 , doi : 10.1002 / jmor.1108 .
  5. ↑ Seilacher, A., Grazhdankin, D and Legouta, A .: Ediacaran biota: The dawn of animal life in the shadow of giant protists . In: Paleontological Research . 7, No. 1, 2003, pp. 43-54.
  6. ↑ Guy M. Narbonne (Aug 2004): Modular Construction of Early Ediacaran Complex Life Forms . Science , Volume 305, pp. 1141-1144, doi: 10.1126 / science.1099727
  7. ↑ Glaessner, Martin F.und Wade, Mary: The late Precambrian fossils from Ediacaran, South Australia . In: Palaeontology . tape 9 (4) , 1966, pp. 599-628 .
  8. ↑ a b c Vickers-Rich, P. et al .: Reconstructing Rangea: New Discoveries from the Ediacaran of Southern Namibia . In: Journal of Paleontology . tape 87 , 2013, p. 1 , doi : 10.1666 / 12-074R.1 .
  9. ↑ Jennifer F. Hoyal Cuthill and Simon Conway Morris: Fractal branching organizations of Ediacaran rangeomorph fronds reveal a lost Proterozoic body plan . In: Proceedings of the National Academy of Sciences . vol. 111, 2014, p. 13122-13126 , doi : 10.1073 / pnas.1408542111 .
  10. ↑ Jenkins, RJF: The enigmatic Ediacaran (Late Precambrian) genus Rangea and related Forms . In: Paleobiology . tape 11 (3) , 1985, pp. 336-355 .
  11. ↑ Grazhdankin, D .: Patterns of distribution in the Ediacaran biotas: facies versus biogeography and evolution . In: Paleobiology . tape 30 (2) , 2004, pp. 203-221 .
  12. ↑ Ivantsov, A. Yu. and Leonov, MV: The imprints of Vendian animals - unique paleontological objects of the Arkhangelsk region (in Russian) . Arkhangelsk 2009, ISBN 978-5-903625-04-8 , pp. 91 .
  13. ↑ Dima Grazhdankin and Adolf Seilacher: A re-examination of the Nama-type Vendian organism Rangea schneiderhoehni . In: Geological Magazine . tape 142 (5) , 2005, doi : 10.1017 / S0016756805000920 .
  14. ↑ a b Laflamme, M., Xiao, S. and Kowalewski, M .: Osmotrophy in modular Ediacara organisms . In: Proceedings of the National Academy of Sciences . tape 106 (34) , 2009, pp. 14438-14443 , doi : 10.1073 / pnas.0904836106 .