|
Praecambridium Sigillum
''Praecambridium sigillum'' is an extinct organism that superficially resembles a segmented trilobite-like arthropod. It was originally described as being a trilobite-like arthropod, though the majority of experts now place it within the Proarticulata as a close relative of the much larger ''Yorgia''. It is from the Late Ediacaran deposit of Ediacara Hills, Australia, about 555 million years ago. On average, ''P. sigillum'' had at least 5 pairs of segments, with each unit becoming progressively larger as they approach the cephalon-like head. Etymology The generic name is a compound word, with the Latin prefix ''prae'' "before" and a reference to the Cambrian mollusc genus '' Cambridium'', in reference to how the appearance of the various segments are reminiscent of the muscle-scars on the inner surface of the shells of '' Cambridium''. The specific name is from Latin ''sigillum'' "a sigil". Classification and interpretations Originally, Runnegar and M.A. Fedokin (1992) suggested ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ediacaran
The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last period of the Proterozoic geologic eon, Eon as well as the last of the so-called "Precambrian supereon", before the beginning of the subsequent Cambrian Period marks the start of the Phanerozoic Eon, where recognizable fossil evidence of life becomes common. The Ediacaran Period is named after the Ediacara Hills of South Australia, where trace fossils of a diverse community of previously unrecognized lifeforms (later named the Ediacaran biota) were first discovered by geologist Reg Sprigg in 1946. Its 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 took namesake from the Ediacara Hills ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seal (emblem)
A seal is a device for making an impression in Sealing wax, wax, clay, paper, or some other medium, including an Paper embossing, embossment on paper, and is also the impression thus made. The original purpose was to authenticate a document, or to prevent interference with a package or envelope by applying a seal which had to be broken to open the container (hence the modern English verb "to seal", which implies secure closing without an actual wax seal). The seal-making device is also referred to as the seal ''matrix'' or ''die''; the imprint it creates as the seal impression (or, more rarely, the ''sealing''). If the impression is made purely as a relief resulting from the greater pressure on the paper where the high parts of the matrix touch, the seal is known as a ''dry seal''; in other cases ink or another liquid or liquefied medium is used, in another color than the paper. In most traditional forms of dry seal the design on the seal matrix is in Intaglio (sculpture), intag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yorgiidae
Yorgiidae is an extinct family of the class Cephalozoa, which is a part of the wider phylum Proarticulata. They lived from around 571 to 551 Ma. Description Like other relatives within the phylum Proarticulata, their body plan consists of isomers arranged in a glide symmetry, meaning they do not have true bilateral symmetry. As with other cephalozoans, their initial right isomer extends right across the body, forming a distinctive 'head', whilst they have a unique feature with their initial left isomer extending slightly to the right side and into the initial right isomer. This is most prominent in the genus ''Archaeaspinus'', with it having an unpaired left lobe/isomer within its 'head' region, forming a distinctive question mark-like shape. Distribution Genera of the family Yorgiidae are most commonly found in the Ust' Pinega Formation and Central Urals of Russia, as well as the Flinders Ranges of South Australia. Taxonomy Yorgiidae includes the following genera: *� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sprigginidae
Sprigginidae is an extinct family of the class Cephalozoa, characterized by having a greater number of isomers than its sister taxon, Yorgiidae. They lived approximately 635 million years ago, in the Ediacaran period. Description Like most members of Proarticulata, their body plan consists of isomers arranged in a glide symmetry, meaning they do not have true bilateral symmetry, although what sets them out from other proarticulates is their greater number of isomers, numbering up to around 40, sometimes more, overall. They also have a distinct 'horseshoe' shaped 'head'. When the first member of the family, ''Spriggina'', was discovered, it was considered to be a polychaete annelid, and petalonamid frond, and even an arthropod, with probable relations to trilobites. Although most recent studies now agree that ''Spriggina'', and the family its apart of, are apart of the phylum Proarticulata. Distribution Most genera are restricted to sediments within the Flinders Ranges of Sou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalozoa
Cephalozoa are an extinct class (biology), class of primitive segmented marine organisms within the Phylum (biology), Phylum Proarticulata from the Ediacaran period. They possessed bilateral symmetry and were characterized by a thin, rounded body. Description Unlike the other classes of proarticulata, proarticulates, the segmentation of the body is not complete and shows a "head" with fine distribution channels. Some species of the Yorgiidae family also show some asymmetry. They were discovered in Russia near the White Sea in the Arkhangelsk region, where they lived during the Ediacaran, approximately 635 to 540 myr, Ma (millions of years ago). Taxonomy Cephalozoa includes the families Yorgiidae and Sprigginidae: Yorgiidae *† ''Archaeaspinus'' Ivantsov, 2007 (synonym of ''Archaeaspis'') **† ''Archaeaspinus fedonkini'' Ivantsov, 2001 *† ''Yorgia'' Ivantsov, 1999 **† ''Yorgia waggoneri'' Ivantsov, 1999 Sprigginidae *† ''Spriggina'' Glaessner, 1958 **† ''Spriggina fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Ediacaran Genera
The existence of life, especially that of animals, before the Cambrian had long been the subject of debate in paleontology. The apparent suddenness of the Cambrian explosion had no firm explanation, and Charles Darwin himself recognized the challenge it posed for his theory of evolution. While reports of Precambrian organisms have been made since Alexander Murray's 1868 discovery of ''Aspidella'', it wasn't until the discovery of ''Charnia'' in 1956 that considerable evidence of Precambrian life had been presented. The period immediately preceding the Cambrian, the Ediacaran, is now widely accepted of containing animal life. It spans from 635 to 540 million years ago, and covers approximately 2% of Earth's history. Taxonomists have purported a total of 245 described genera from the Ediacaran, 162 of which are accepted as valid. Key * Valid genus - Genera that are accepted by the scientific community * Synonym (taxonomy), Junior synonym - Alternative name for an already existi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Agnostida
Agnostida are an order of extinct arthropods which have classically been seen as a group of highly modified trilobites, though some recent research has doubted this placement. Regardless, they appear to be close relatives as part of the Artiopoda. They are present in the Lower Cambrian fossil record along with trilobites from the Redlichiida, Corynexochida, and Ptychopariida orders, and were highly diverse throughout the Cambrian. Agnostidan diversity severely declined during the Cambrian-Ordovician transition, and the last agnostidans went extinct in the Late Ordovician. Systematics The Agnostida are divided into two suborders — Agnostina and Eodiscina — which are then subdivided into a number of families. As a group, agnostids are isopygous, meaning their pygidium is similar in size and shape to their cephalon. Most agnostid species were eyeless. The systematic position of the order Agnostida within the class Trilobita remains uncertain, and there has been c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annelid
The annelids (), also known as the segmented worms, are animals that comprise the phylum Annelida (; ). The phylum contains over 22,000 extant species, including ragworms, earthworms, and leeches. The species exist in and have adapted to various ecologies – some in marine environments as distinct as tidal zones and hydrothermal vents, others in fresh water, and yet others in moist terrestrial environments. The annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms. They also have parapodia for locomotion. Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species. Cladistic research since 1997 has radically changed this scheme, viewing leeches as a sub-group of oligochaetes and oligochaetes as a sub-group of polychaetes. In addition, the Pogonophora, Echiura and Sipuncula, previously regarded as separate phyla, are now regarded as sub-grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dickinsonia
''Dickinsonia'' is a genus of extinct organism that lived during the late Ediacaran period in what is now Australia, China, Russia, and Ukraine. It had a round, bilaterally symmetric body with multiple segments running along it. It could range from a few millimeters to over a meter in length, and likely lived in shallow waters, feeding on the microbial mats that dominated the seascape at the time. As a member of the Ediacaran biota, its relationships to other organisms has been heavily debated. It was initially proposed to be a jellyfish, and over the years has been claimed to be a land-dwelling lichen, placozoan, or even a giant protist. Currently, the most popular interpretation is that it was a seafloor dwelling animal, perhaps a primitive stem group bilaterian, although this is still contentious. Among other Ediacaran organisms, it shares a close resemblance to other segmented forms like '' Vendia'', Yorgia and '' Spriggina'' and has been proposed to be a member of the ph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelicerate
The subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. Chelicerates include the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids. Chelicerata split from Mandibulata by the mid-Cambrian, as evidenced by stem-group chelicerates like Habeliida and '' Mollisonia'' present by this time. The surviving marine species include the four species of xiphosurans (horseshoe crabs), and possibly the 1,300 species of pycnogonids (sea spiders), if the latter are indeed chelicerates. On the other hand, there are over 77,000 well-identified species of air-breathing chelicerates, and there may be about 500,000 unidentified species. Like all arthropods, chelicerates have segmented bodies with jointed limbs, all covered in a cuticle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
South Australia
South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which includes some of the most arid parts of the continent, and with 1.8 million people. It is the fifth-largest of the states and territories by population. This population is the second-most highly centralised in the nation after Western Australia, with more than 77% of South Australians living in the capital Adelaide or its environs. Other population centres in the state are relatively small; Mount Gambier, the second-largest centre, has a population of 26,878. South Australia shares borders with all the other mainland states. It is bordered to the west by Western Australia, to the north by the Northern Territory, to the north-east by Queensland, to the east by New South Wales, to the south-east by Victoria (state), Victoria, and to the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marywadea
''Marywadea'' is a genus of Ediacaran biota shaped like an oval with a central ridge. It is a bilaterian organism as evidenced by its symmetry, vaguely resembling a very primitive trilobite. The fossil has an asymmetrical first chamber of the quilt. It has transverse ridges away from the central axis that may be gonads. The head is shaped as a semicircle and is the same width as the rest of the body. The ridges number about 50. There are two oval shapes below the head. ''Marywadea ovata'' is the only described species of the genus. Originally ''M. ovata'' was grouped under the genus '' Spriggina'', but later research moved the species into its own genus. It is most often interpreted as an early arthropod, annelid, or a member of Proarticulata, but as with all Ediacarian fauna its phylogeny remains uncertain. Initially, it was described as the second species of '' Spriggina''. The genus was established by Martin Glaessner in 1976, who named it after fellow paleontologist Mary ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
