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End-Ediacaran Extinction
The end-Ediacaran extinction is a mass extinction believed to have occurred near the end of the Ediacaran period, the final period of the Proterozoic eon. Evidence suggesting that such a mass extinction occurred includes a massive reduction in diversity of acritarchs, the sudden disappearance of the Ediacara biota and calcifying organisms, and the time gap before Cambrian organisms "replaced" them. Some lines of evidence suggests that there may have been two distinct pulses of the extinction event, one occurring and the other . Evidence Biotic evidence Ediacaran organisms During the Ediacaran period, two main groups of organisms are found in the fossil record: the "Ediacaran biota" of soft-bodied organisms, preserved by microbial mats; and calcifying organisms such as '' Cloudina'' and ''Namacalathus'', which had a carbonate skeleton. Because ''both ''these groups disappear abruptly at the end of the Ediacaran period, , their disappearance cannot simply represent the closure of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ediacaran
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 bio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holdfast (biology)
A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate. Holdfasts vary in shape and form depending on both the species and the substrate type. The holdfasts of organisms that live in muddy substrates often have complex tangles of root-like growths. These projections are called haptera and similar structures of the same name are found on lichens. The holdfasts of organisms that live in sandy substrates are bulb-like and very flexible, such as those of sea pens, thus permitting the organism to pull the entire body into the substrate when the holdfast is contracted. The holdfasts of organisms that live on smooth surfaces (such as the surface of a boulder) have flattened bases which adhere to the surface. The organism derives no nutrition from this intimate contact with the substrate, as the process of liberating nutrients from the substrate requires ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petrology: Igneous, Sedimentary and Metamorphic'', 2nd ed., Freeman, pp. 281–292 Shale is characterized by its tendency to split into thin layers ( laminae) less than one centimeter in thickness. This property is called '' fissility''. Shale is the most common sedimentary rock. The term ''shale'' is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the more narrow sense of clay-rich fissile mudrock. Texture Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable bed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palaeoworld
''Palaeoworld'' is a peer-reviewed academic journal with a focus on palaeontology and stratigraphy research in and around China. It was founded in 1991 by the Nanjing Institute of Geology and Palaeontology at the Chinese Academy of Sciences (NIGPAS). The journal has been published quarterly since 2006; prior to 2006, it did not adhere to a fixed publication schedule. The journal publishes articles from several specialised fields pertaining to palaeobiology and earth science, such as: fossil taxonomy; biostratigraphy, chemostratigraphy, and chronostratigraphy; evolutionary biology; evolutionary ecology; palaeoecology; palaeoclimatology; and molecular palaeontology. Its editors-in-chief are Shuzhong Shen of the State Key Laboratory of Palaeobiology and Stratigraphy at NIGPAS, and Norman MacLeod of the Natural History Museum, London. See also * ''Paleontological Journal'' * List of fossil sites References External links * (Elsevier.com) * (ScienceDirect ScienceDirect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shuram Excursion
The Shuram excursion, or Shuram-Wonoka excursion, is a change in δ13C, or in the ratio of carbon-13 to carbon-12, taking place between around 573 and 562 million years ago, during the Ediacaran Period. It was first noticed in the Wonoka Formation in South Australia in 1990 and later in the Shuram Formation in Oman in 1993. It is the largest negative δ13C excursion in Earth history, and recovery took 50 million years, although the apparent magnitude of the excursion may be distorted due to meteoric water diagenesis. It is not known what caused the excursion. The Shuram excursion may have played a role in sparking the rise of animals that resulted later in the Cambrian explosion The Cambrian explosion, Cambrian radiation, Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately in the Cambrian Period when practically all major animal phyla started appearing in the fossil record. .... The oxygen-consuming Ediacara biota experienced a ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spriggina
''Spriggina'' is a genus of early bilaterian animals whose relationship to living animals is unclear. Fossils of ''Spriggina'' are known from the late Ediacaran period in what is now South Australia. ''Spriggina floundersi'' is the official fossil emblem of South Australia. It has been found nowhere else. The organism reached about in length and may have been predatory. Its bottom was covered with two rows of tough interlocking plates, while one row covered its top; its front few segments fused to form a "head." ''Spriggina'' affinity is currently unknown; it has been variously classified as an annelid worm, a rangeomorph-like frond, a variant of ''Charniodiscus'', a proarticulatan, or an arthropod perhaps related to the trilobites, or even an extinct phylum. Lack of known segmented legs or limbs, and glide reflection instead of symmetric segments, suggest an arthropod classification is unlikely despite some superficial resemblance. The genus ''Spriggina'' may have origin ... [...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 ou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protonympha
''Protonympha'' is a form genus for problematic fossils of Devonian age in New York. It has been of special interest because of its morphological similarity with the iconic Ediacaran fossil ''Spriggina'', and may have been a late surviving vendobiont. Description ''Protonympha'' is a flat, quilted fossil, which has previously been compared with the arm of a starfish or an annelid worm, but lacks a segmented carapace or stereom. Its preservation in sandstone is similar to Ediacaran type preservation Ediacaran type preservation relates to the dominant preservational mode in the Ediacaran period, where Ediacaran organisms were preserved as casts on the surface of microbial mats. Exceptional preservation All but the smallest fraction of the ...s.J. J. Sepkoski. 2002. A compendium of fossil marine animal genera. Bulletins of American Paleontology 363:1-560 A less-accepted hypothesis claims the organisms were terrestrial fossils like lichen, with hypothetically interpreted r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rutgersella
''Rutgersella truexi'' is a form species for problematic fossils of Early Silurian age in Pennsylvania. It has been of special interest because of its morphological similarity with the iconic Ediacaran fossil ''Dickinsonia'', and may have been a late surviving vendobiont. Description ''Rutgersella truexi'' is a flat, segmented fossil, with both radial and bilateral symmetry like ''Dickinsonia'', but with a shorter midline. The fossils are pyritized; some internal chambers are filled with chalcedony, so that they are preserved along with proposed "basal rhizines". Controversially, according to Retallack, these observations suggest affinities with lichens, and perhaps the fungal phylum Glomeromycota Glomeromycota (often referred to as glomeromycetes, as they include only one class, Glomeromycetes) are one of eight currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromyco ..., a statement not currentl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ventogyrus
''Ventogyrus'' is an Ediacaran fossil found in the White Sea-Arkhangelsk region of Russia. It was first discovered in the Teska member of the Ust'-Pinega formation, in a thick lens of sandstone, originally sand dumped by storm waves that cut a deep channel through the shallow sea bottom where the organisms lived. Many individuals were preserved on top of each other, often torn or in distorted positions. As a result, it was originally thought to have had a "boat shaped" form and to have lived anchored in the sea floor. However, a nearby site discovered later by Mikhail Fedonkin yielded separate specimens which were beautifully preserved in an upright position and showed the internal anatomy. Ventogyrus is now believed to have lived on or above the sea floor, an egg-shaped organism made of three modules (like the sections of an orange), all connected to a central rod. This three-fold, or triradial, symmetry is not usually found in the living world today, but it is also seen in othe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erytholus
''Erytholus'' is a form genus for problematic fossils of Cambrian age in South Australia. It has been of special interest because of its morphological similarity with the Ediacaran fossil ''Ventogyrus'', and may have been a late surviving vendobiont. It could be a slime mold. Description ''Erytholus'' is a globose, chambered fossil, with associated vertical tubular structures. Its preservation in sandstone is similar to the Ediacaran type preservation of the vendobiont ''Ventogyrus''. It is found at depths of within paleosols. Its affinities are uncertain, although it bears a general resemblance to truffles A truffle is the fruiting body of a subterranean ascomycete fungus, predominantly one of the many species of the genus ''Tuber''. In addition to ''Tuber'', many other genera of fungi are classified as truffles including '' Geopora'', '' Pe .... References Cambrian fossil record Controversial taxa {{Paleo-biota-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swartpuntia
''Swartpuntia'' is a monospecific genus of erniettomorph from the terminal Ediacaran period, with at least three quilted, leaf-shaped petaloids — probably five or six. The petaloids comprise vertical sheets of tubes filled with sand. ''Swartpuntia'' specimens range in length from 12 to 19 cm, and in width from 11.5 to 140 cm. The margin is serrated, with a 1 mm wide groove. A 14 mm wide stem extends down the middle, tapering towards the top, and stopping 25 mm from the tip. The stem has a V shaped ornamentation on it. The original fossils were found at, and named after, the Swartpunt farm between Aus and Rosh Pinah in Namibia. The generic name comes from ''Swartpunt'', meaning ''black point'' in reference to the colour of the rocks. The specific name ''germsi'' honours Gerard Germs, who studied the Nama formation of geological beds. They are preserved in sandstone beds in the Spitzkopf Member from the Nama formation, which lie above an ash ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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