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Dipleurozoa
Dipleurozoa (or Dickinsoniomorpha) are extinct proarticulate organisms of the Ediacaran period, which had a flat and more or less ovoid shape. Polychaete worms were treated, however it seems more likely that they were vendobionts. The most representative genus is '' Dickinsonia'', which gives the name to the class (in the case of Dickinsoniomorpha).Seilacher, A., « Vendobionta and Psammocorallia: lost constructions of Precambrian evolution », Journal of the Geological Society, London, vol. 149, no 4, 1992, p. 607-613 (ISSN 0016-7649, DOI 10.1144/.gsjgs.149.4.0607, lire en ligne At first glance, the organisms appear to be bilateral that are made up of serial segments. However, this can be misleading, as there are indications that the structures to the left and right of the body axis were not arranged in pairs, but offset each other alternately; like the segments of many rangeomorphs. They show a front and a back end, the footprints indicate some capacity for movement. The prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipleurozoa
Dipleurozoa (or Dickinsoniomorpha) are extinct proarticulate organisms of the Ediacaran period, which had a flat and more or less ovoid shape. Polychaete worms were treated, however it seems more likely that they were vendobionts. The most representative genus is '' Dickinsonia'', which gives the name to the class (in the case of Dickinsoniomorpha).Seilacher, A., « Vendobionta and Psammocorallia: lost constructions of Precambrian evolution », Journal of the Geological Society, London, vol. 149, no 4, 1992, p. 607-613 (ISSN 0016-7649, DOI 10.1144/.gsjgs.149.4.0607, lire en ligne At first glance, the organisms appear to be bilateral that are made up of serial segments. However, this can be misleading, as there are indications that the structures to the left and right of the body axis were not arranged in pairs, but offset each other alternately; like the segments of many rangeomorphs. They show a front and a back end, the footprints indicate some capacity for movement. The prin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proarticulata
Proarticulata is a proposed phylum of extinct, bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately . The name comes from the Greek () = "before" and Articulata, i.e. prior to animals with true segmentation such as annelids and arthropods. This phylum was established by Mikhail A. Fedonkin in 1985 for such animals as '' Dickinsonia'', ''Vendia'', ''Cephalonega'', ''Praecambridium'' and currently many other Proarticulata are described (see list). Due to their simplistic morphology, their affinities and mode of life are subject to debate. They are almost universally considered to be metazoans, and due to possessing a clear central axis have been suggested to be stem-bilaterians. In the traditional interpretation, the Proarticulatan body is divided into transverse articulation (division) into isomers as distinct from the transverse articulation segments in annelids and arthropods, as their individual isome ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dickinsonia
''Dickinsonia'' is an extinct genus of basal animal that lived during the late Ediacaran period in what is now Australia, China, Russia and Ukraine. The individual ''Dickinsonia'' typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth is consistent with a stem-group bilaterian affinity, though some have suggested that it belongs to the fungi, or even an "extinct kingdom". It lived during the late Ediacaran (part of Precambrian). The discovery of cholesterol molecules in fossils of ''Dickinsonia'' lends support to the idea that ''Dickinsonia'' was an animal. Description ''Dickinsonia'' fossils are known only in the form of imprints and casts in sandstone beds. The specimens found range from a few millimetres to about in length, and from a fraction of a millimetre to a few millimetres thick. They are nearly bilaterally symmetric, segmented, round or oval in outline, slightly expanded to one end (i.e. egg-shaped out ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dickinsonia Costata
''Dickinsonia'' is an extinct genus of basal animal that lived during the late Ediacaran period in what is now Australia, China, Russia and Ukraine. The individual ''Dickinsonia'' typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth is consistent with a stem-group bilaterian affinity, though some have suggested that it belongs to the fungi, or even an "extinct kingdom". It lived during the late Ediacaran (part of Precambrian). The discovery of cholesterol molecules in fossils of ''Dickinsonia'' lends support to the idea that ''Dickinsonia'' was an animal. Description ''Dickinsonia'' fossils are known only in the form of imprints and casts in sandstone beds. The specimens found range from a few millimetres to about in length, and from a fraction of a millimetre to a few millimetres thick. They are nearly bilaterally symmetric, segmented, round or oval in outline, slightly expanded to one end (i.e. egg-shaped out ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Windermeria
''Windermeria aitkeni'' (named after Windermere, British Columbia, Canada) is a Precambrian organism from the Blueflower Formation of Sekwi Brook North, in the Northwest Territories of Canada. Only one specimen has been found. ''Windermeria'' is a small (16.4 × 7.9 mm) segmented elongated oval fossil with eight nearly equal-sized segments arranged transverse to medial furrow in opposite arrangement.Fedonkin M.A., Gehling J.G., Grey K., Narbonne G.M., Vickers-Rich P. (2007).The Rise of Animals: Evolution and Diversification of the Kingdom Animalia, Johns Hopkins University Press. pp. 292 ''Windermeria'' superficially resembles a diminutive '' Dickinsonia'' and as such is the only possible dickinsoniid proarticulatan known exclusively from outside of Australia and East Europe.Narbonne G.M. (2007).Chapter 10. The Canadian Cordillera. In: Fedonkin M.A., Gehling J.G., Grey K., Narbonne G.M., Vickers-Rich P. "The Rise of Animals: Evolution and Diversification of the Kingdom An ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dickinsoniidae
Dickinsoniidae is a taxon of Ediacaran fossils with an airbed-like quilted morphology, sometimes found in association with bizarre trace fossils. It is placed within the extinct phylum Proarticulata, and contains the defined genera '' Dickinsonia'' and probably ''Windermeria''. '' Phyllozoon'' is associated with this family, and is thought to represent ichnofossil A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...s of ''Dickinsonia''. References Ediacaran life Prehistoric animal families Ediacaran first appearances {{Precambrian-animal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ediacaran Period
The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and the beginning of the Phanerozoic Eon. It is named after the Ediacara Hills of South Australia. The Ediacaran Period's status as an official geological period was ratified in 2004 by the International Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years. Although the period takes its name from the Ediacara Hills where geologist Reg Sprigg first discovered fossils of the eponymous Ediacaran biota in 1946, the type section is located in the bed of the Enorama Creek within Brachina Gorge in the Flinders Ranges of South Australia, at . The Ediacaran marks the first appearance of widespread multicellular fauna following the end of Snowball Earth glaciation events, the so-called Ediacaran biota, wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polychaete
Polychaeta () is a paraphyletic class (biology), class of generally marine invertebrate, marine annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. More than 10,000 species are described in this class. Common representatives include the lugworm (''Arenicola marina'') and the Alitta virens, sandworm or Alitta succinea, clam worm ''Alitta''. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the extremely high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen (still unclassified) observed by the robot ocean probe Nereus (underwater vehicle), ''Nereus'' at the bottom of the Challenger Deep, the deepes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vendobiont
Vendobionts or Vendozoans (Vendobionta) are a proposed very high-level, extinct clade of benthic organisms that made up of the majority of the organisms that were part of the Ediacaran biota. It is a hypothetical group and at the same time, it would be the oldest of the animals that populated the Earth about 580 million years ago, in the Ediacaran period (formerly ''Vendian''). They became extinct shortly after the so-called Cambrian explosion, with the introduction of fauna formed by more recognizable groups and more related to modern animals. It is very likely that the whole Ediacaran biota is not a monophyletic clade and not every genus placed in its subtaxa is an animal. This biological group is not widely recognized; credibility is limited by the expansive speculation needed to establish phylogenetic relationships between such ancient extinct groups. The hypothesis was formulated by the German geologist Adolf Seilacher, who even doubts its relationship with the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rangeomorph
The rangeomorphs are a form taxon of frondose Ediacaran Ediacaran biota, fossils that are united by a similarity to ''Rangea''. Some researchers, such as Pflug and Narbonne, suggest that a natural taxon Rangeomorpha may include all similar-looking fossils. Rangeomorphs appear to have had an effective reproductive strategy, based on analysis of the distribution pattern of ''Fractofusus misrai'', which consisted of sending out a waterborne asexual propagule to a distant area, and then spreading rapidly from there, just as plants today spread by stolons or runners. Rangeomorphs are a key part of the Ediacaran biota, which survived about 30 million years, until the base of the Cambrian, which was . They were especially abundant in the early Ediacaran Mistaken Point assemblage found in Newfoundland (island), Newfoundland. Body plan Rangeomorphs consist of branching "frond" elements, each a few centimetres long, each of which is composed of many smaller branching tubes held up by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placozoa
The Placozoa are a basal form of marine free-living (non-parasitic) multicellular organism. They are the simplest in structure of all animals. Three genera have been found: the classical ''Trichoplax adhaerens'', ''Hoilungia hongkongensis'', and ''Polyplacotoma mediterranea'', where the last appears most basal. The last two have been found only since 2017. Although the Placozoa were first discovered in 1883 by the German zoologist Franz Eilhard Schulze (1840–1921) and since the 1970s more systematically analyzed by the German protozoologist Karl Gottlieb Grell (1912–1994), a common name does not yet exist for the taxon; the scientific name means "flat animals". Biology ''Trichoplax'' is a small, flattened, animal around across. An amorphous multi-celled body, analogous to a single-celled ''Amoeba'', it has no regular outline, although the lower surface is somewhat concave, and the upper surface is always flattened. The body consists of an outer layer of simple epithelium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
