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Isomer (Proarticulata)
Isomer (Greek ''isos'' = "equal", ''méros'' = "part") is an element of transverse body articulation of the bilateral fossil animals of the Phylum Proarticulata from the Ediacaran (Vendian) period. This term has been proposed by Andrey Yu. Ivantsov, a Russian paleontologist from the Laboratory of the Precambrian organisms, Paleontological Institute, Russian Academy of Sciences. Morphology Proarticulatan isomers are distinct from the segments of the Annelida and Panarthropoda, as each of these elements occupies only half of width of a body and are organized in an alternating pattern relatively to the axis of the body. In other words, although proarticulatans are bilaterally symmetrical, one side is not the direct mirror image of its opposite. Opposite isomers of left and right side are located with displacement of half of its width. This phenomenon is described as the symmetry of gliding reflection.M. A. Fedonkin (1985). "Systematic Description of Vendian Metazoa". In Sokolov, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yorgia
''Yorgia waggoneri'' is a discoid Ediacaran organism. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of . It is classified within the extinct animal phylum Proarticulata. Etymology The generic name ''Yorgia'' comes from the Yorga river on the Zimnii Bereg (Winter Coast) of the White Sea, where the first specimens were found. The specific name ''Yorgia waggoneri'' honors the American paleontologist Ben Waggoner, who found the first specimen. Morphology The body plan of the ''Yorgia'' and other proarticulates is unusual for solitary (non-colonial) metazoans. These bilateral organisms have segmented metameric bodies, but left and right transverse elements (isomers) are organized in an alternating pattern relatively to the axis of the body – they are not direct mirror images. This phenomenon is described as the symmetry of glide reflection, which is a characteristic also found in the similar ''Spr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proarticulata Classes
Proarticulata is a proposed phylum of extinct, near-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 individu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalonega Stepanovi
''Cephalonega stepanovi'' is a fossil organism from Ediacaran deposits of the Arkhangelsk Region, Russia. It was described by Mikhail A. Fedonkin in 1976 Name Its original genus name ''Onega'' comes from the Onega Peninsula of the White Sea, where the first fossils were found. The species name was given to honour V.A. Stepanov, who discovered the Ediacaran fossil site on the Letniy Bereg (" Summer Coast") in 1972, on the Onega Peninsula, the first Proterozoic site found in the Arkhangelsk Oblast. The original generic name is previously occupied by the hemipteran genus ''Onega'' Distant (1908). Ivantsov ''et al.'' (2019) coined a replacement generic name ''Cephalonega''. Morphology The small fossils, which range up to long, have oval outlines and low bodies with an articulated central zone built of isomers encircled by an undivided zone. The surface of the undivided region of ''Cephalonega'' is covered with small tubercles. ''Cephalonega'' was originally described by Mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phyllozoon
''Phyllozoon'' (lit. "Leaf animal" in Greek) is an Ediacaran imprint that resembles a proarticulatan and has been interpreted as a feeding trace. It usually occurs in long chains of imprints formed, presumably as the organism that made it moved. See also *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 chal ... References Fossils of Australia Dipleurozoa Ediacaran life Fossil taxa described in 1978 Trace fossils {{precambrian-animal-stub ... [...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] |
Family (biology)
Family (, : ) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as the "walnut family". The delineation of what constitutes a family—or whether a described family should be acknowledged—is established and decided upon by active taxonomists. There are not strict regulations for outlining or acknowledging a family, yet in the realm of plants, these classifications often rely on both the vegetative and reproductive characteristics of plant species. Taxonomists frequently hold varying perspectives on these descriptions, leading to a lack of widespread consensus within the scientific community ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanorus
''Cyanorus singularis'' is a small proarticulatan, closely related to ''Spriggina'' and ''Marywadea''. The anterior part of the body was most likely not segmented. The axial structure of it combines features of the ''Vendia'' species and ''Dickinsonia'' species. It was found in the Upper Vendian of the White Sea area, Arkhangel'sk Region. It is a White Sea Ediacaran fossil and it became extinct during the Late Precambrian. Like other animals from the phylum Proarticulata, the symmetry observed is not exactly bilaterian but appears to be a glide reflection In geometry, a glide reflection or transflection is a geometric transformation that consists of a reflection across a hyperplane and a translation ("glide") in a direction parallel to that hyperplane, combined into a single transformation. Bec ..., where opposite segments are shifted by half an interval. Notes References {{Taxonbar, from=Q60760937 Ediacaran life Sprigginidae ... [...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] |
Spriggina
''Spriggina'' is a genus of early 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 in length and may have been predation, 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." The affinity of ''Spriggina'' is unknown; it has been variously classified as an annelid worm, a rangeomorph-like frond, a variant of ''Charniodiscus'', a proarticulatan, an arthropod (perhaps related to the trilobites), or even an extinct phylum. The lack of known segmented legs or limbs, coupled with the presence of glide reflection instead of symmetry, symmetric segments, suggests that an arthropod classification is unlikely despite some superficial resemblance. The genu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ivovicia
''Ivovicia'' is an extinct genus of proarticulates. This monotypic genus has only one species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...: ''Ivovicia rugulosa''. The genus is named after the Ivovik creek, near the location where the specimen was found. Etymology The generic name, ''Ivovicia'', refers to the Ivovik Creek, which is located near the type locality of ''I. rugulosa''. The specific name, ''rugulosa'', is from Latin ''rugulosus'', meaning 'finely wrinkled'. Therefore, the scientific name ''Iovicia rugulosa'' can roughly be translated as 'finely wrinkled of Ivovik Creek'. References Notes Budd, Graham E.; Jensen, Sören. The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution. Biological Reviews November 2015.Freeman, Gary. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeaspinus
''Archaeaspinus fedonkini'' is an extinct proarticulatan organism from the Late Ediacaran period. Background ''Archaeaspinus'' was discovered in Zimnii Bereg, the Winter Coast of the White Sea in Russia, by A. Yu. Ivantsov in 2001. Since then, numerous additional fossils have been attributed to the genus, mostly from that same type locality, but a small number from Flinders Ranges in 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 in ... as well. Originally called '' Archaeaspis''—a name already applied to a redlichiid trilobite—in 2001 by Ivantsov, it was later recombined under its current name in 2007 by the same author. The type species, ''A. fedonkini'', is the only species known in this genus. It appears in the fossil record between 571-551Ma. Descrip ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andiva
''Andiva ivantsovi'' is a Vendian fossil, identified to be a bilaterian triploblastic animal in the Ediacaran phylum Proarticulata, known from the Winter Coast, White Sea, Russia. It was first discovered in 1977, and described as a new species in a new genus by Mikhail Fedonkin in 2002. It lived about 555 million years ago. Fossils of ''Andiva'' also occur in South Australia. All known fossils of ''Andiva'' are external molds. Description ''Andiva'' was between long and from wide, with a bilaterally symmetrical shape, larger on the anterior end and narrower at the posterior. The anterior part features a smooth "fringe" followed by a surface "covered by fine ribs and sutura", also described as a "quilt" with narrow, tightly packed chambers The symmetry of these ribs is a glide symmetry, that is, in which the corresponding segments on the left and right sides do not line up, but are staggered. This is a feature shared by other forms belonging to the proposed taxon Proartic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
