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Namacalathus
''Namacalathus'' is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, ''N. hermanastes'', was first described in 2000 from the Nama Group of central and southern Namibia. A U–Pb zircon age from the fossiliferous rock in Namibia and Oman provides an age for the ''Namacalathus'' zone in the range from 549 to 542 Ma, which corresponds to the Late Ediacaran. Alongside ''Namapoikia'' and '' Cloudina'', these organisms are the oldest known evidence in the fossil record of the emergence of calcified skeletal formation in metazoans, a prominent feature in animals appearing later in the Early Cambrian. Shore ''et al.'' (2021) reported the first three-dimensional, pyritized preservation of soft tissue in ''Namacalathus hermanastes'' from the Nama Group (Namibia), and evaluate the implications of this finding for the knowledge of the phylogenetic relationships of this animal; they suggest it is an ancestor of Lophotrochozoan animals su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nama Group
The Nama Group is a megaregional Vendian to Cambrian group of stratigraphic sequences deposited in the Nama foreland basin in central and southern Namibia. The Nama Basin is a peripheral foreland basin, and the Nama Group was deposited in two early basins, the Zaris and Witputs, to the north, while the South African Vanrhynsdorp Group was deposited in the southern third. The Nama Group is made of fluvial and shallow-water marine sediments, both siliciclastic and carbonate. La Tinta Group in Argentina is considered equivalent to Nama Group. Description The group extends from the Gariep Belt in the south to outcrops of pre- Damara basement in the north.Meert et al., 1997, p.639 Thrombolite-stromatolite reefs in the Nama Group are best developed in the Kuibis Subgroup of the Zaris subbasin, and in the Huns platform of the Witputs subbasin. The Nama Group is a series of interbedded shallow marine carbonates and siliciclastics deposited in a storm-dominated ramp setting.Wood & Cur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Namapoikia
''Namapoikia rietoogensis'' is among the earliest known animals to produce a calcareous (probably aragonite) skeleton. Known from the Ediacaran period, before the Cambrian explosion of calcifying animals, the long-lived organism grew up to a metre in diameter and resembles a colonial sponge. It was an encruster, filling vertical fissures in the reefs in which it originally grew. The fossil was first found in the Omkyk Member of the Nama Group from Rietoog in southern Namibia, in association with other calcifying fossils, '' Cloudina'' and ''Namacalathus''. Its mineralogy and accretionary style has been compared with that of the Lophotrochozoans, though its unfamiliar morphology suggests a stem-group or deeper affiliation to this group. It grew in spurts, first emplacing an organic skeleton, then filling this in with aragonite. See also * Ediacaran biota * Namacalathus * Cloudina * List of Ediacaran genera This is a list of all described Ediacaran genera, including the Edi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ediacaran Life
The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The Ediacaran biota may have undergone evolutionary radiation in a proposed event called the Avalon explosion, . This was after the Earth had thawed from the Cryogenian period's extensive glaciation. This biota largely disappeared with the rapid increase in biodiversity known as the Cambrian explosion. Most of the currently existing body plans of animals first appeared in the fossil record of the Cambrian rather than the Ediacaran. For macroorganisms, the Cambrian biota appears to have almost completely replaced the organisms that dominated the Ediacaran fossil record, although relationships are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Cambrian
The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established as "Cambrian series" by Adam Sedgwick, who named it after Cambria, the Latin name for 'Cymru' (Wales), where Britain's Cambrian rocks are best exposed. Sedgwick identified the layer as part of his task, along with Roderick Murchison, to subdivide the large "Transition Series", although the two geologists disagreed for a while on the appropriate categorization. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Ediacaran Genera ...
This is a list of all described Ediacaran genera, including the Ediacaran biota. It contains 227 genera. References {{reflist, 30em * 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 th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stromatolites
Stromatolites () or stromatoliths () are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Although they are rare today, fossilized stromatolites provide records of ancient life on Earth. Morphology Stromatolites are layered, biochemical, accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains in biofilms (specifically microbial mats), through the action of certain microbial lifeforms, especially cyanobacteria. They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, and branching ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trace Fossil
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, which are the fossilized remains of parts of organisms' bodies, usually altered by later chemical activity or mineralization. The study of such trace fossils is ichnology and is the work of ichnologists. Trace fossils may consist of impressions made on or in the substrate by an organism. For example, burrows, borings (bioerosion), urolites (erosion caused by evacuation of liquid wastes), footprints and feeding marks and root cavities may all be trace fossils. The term in its broadest sense also includes the remains of other organic material produced by an organism; for example coprolites (fossilized droppings) or chemical markers (sedimentological structures produced by biological means; for example, the formation of stromatolites). H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formation), and the changes that may occur in those attributes over a geographic area. A facies encompasses all of the characteristics of a rock including its chemical, physical, and biological features that distinguish it from adjacent rock. The term facies was introduced by the Swiss geologist Amanz Gressly in 1838 and was part of his significant contribution to the foundations of modern stratigraphy, which replaced the earlier notions of Neptunism. Types of facies Sedimentary facies Ideally, a Sedimentary structures, sedimentary facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment. Sedimentary facies are either descriptive or interpretative. Sedimentary facies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geological Unit
A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize it. Units must be ''mappable'' and ''distinct'' from one another, but the contact need not be particularly distinct. For instance, a unit may be defined by terms such as "when the sandstone component exceeds 75%". Lithostratigraphic units Sequences of sedimentary and volcanic rocks are subdivided the basis of their shared or associated lithology. Formally identified lithostratigraphic units are structured in a hierarchy of lithostratigraphic rank, higher rank units generally comprising two or more units of lower rank. Going from smaller to larger in rank, the main lithostratigraphic ranks are Bed, Member, Formation, Group and Supergroup. Formal names of lithostratigraphic units are assigned by geological surveys. Units of formation or hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "the depths." Organisms living in this zone are called benthos and include microorganisms (e.g., bacteria and fungi) as well as larger invertebrates, such as crustaceans and polychaetes. Organisms here generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud. Description Oceans The benthic region of the ocean begins at the shore line (intertidal ... [...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] |
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