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Marywadea Ovata
''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 Wade, ... [...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] |
Arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metamerism (biology), metameric) Segmentation (biology), segments, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They form an extremely diverse group of up to ten million species. Haemolymph is the analogue of blood for most arthropods. An arthropod has an open circulatory system, with a body cavity called a haemocoel through which haemolymph circulates to the interior Organ (anatomy), organs. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. They have ladder-like nervous systems, with paired Anatomical terms of location#Dorsal and ventral, ventral Ventral nerve cord, nerve cord ... [...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 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 term "Ediacara biota" has received criticism from some scientists due to its alleged inconsistency, arbitrary exclusion of certain fossils, and inability to be precisely defined. 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. ... [...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] |
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] |
Mary Julia Wade
Mary Julia Wade (3 February 1928 – 14 September 2005) was an Australian palaeontologist, known for her role as the Deputy Director of the Queensland Museum. Some of her most renowned work was on the Precambrian Ediacaran Biota in South Australia. Wade was born in Adelaide, South Australia and spent her early life on a property in the northeast of the state. She lived the typical country girl's life, it is said. Her family moved when she was seven to Thistle Island in Spencer Gulf where she first became interested in geology. She studied geology and biology at the University of Adelaide, and in 1954, completed a Bachelor of Science with Honors in Micropalaeontology. Wade worked as a Senior Demonstrator at the University, while completing her Doctorate of Philosophy in 1959. Studying remotely via correspondence, Wade was sent on scholarship to the Wilderness School in Adelaide as a boarder from the age of 13. After she finished school, she undertook a Bachelor of Science in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogeny
A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA. In other words, it is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among various biological species or other entities based upon similarities and differences in their physical or genetic characteristics. In evolutionary biology, all life on Earth is theoretically part of a single phylogenetic tree, indicating common ancestry. Phylogenetics is the study of phylogenetic trees. The main challenge is to find a phylogenetic tree representing optimal evolutionary ancestry between a set of species or taxa. computational phylogenetics, Computational phylogenetics (also phylogeny inference) focuses on the algorithms involved in finding optimal phylogenetic tree in the phylogenetic landscape. Phylogene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proarticulata
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] |
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] |
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] |
Martin Glaessner
Martin Fritz Glaessner AM (25 December 1906 – 23 November 1989) was a geologist and palaeontologist. Born and educated in the Austro-Hungarian Empire, he spent the majority of his life in working for geoscientific institutes in Austria, Russia, Australia, and studying the geology of the South Pacific in Papua New Guinea and Australia. Glaessner also did early work on the classification of the pre-Cambrian lifeforms now known as the Ediacaran biota, which he proposed were the early antecedents of modern lifeforms. Life and career Glaessner was born in Aussig in the former Kingdom of Bohemia of the Austro-Hungarian Empire (now in the Czech Republic). He was a research associate at the in Vienna from 1923 to 1932, and starting in 1925, attended the University of Vienna, where he received a doctorate in law in 1929, and a Ph.D. in geology and paleontology in 1931. He was a research associate at the Natural History Museum in London from 1930 to 1931. In 1932, he moved to Mosco ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monotypic Taxon
In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of Genus, genera, the term "unispecific" or "monospecific" is sometimes preferred. In botanical nomenclature, a monotypic genus is a genus in the special case where a genus and a single species are simultaneously described. Theoretical implications Monotypic taxa present several important theoretical challenges in biological classification. One key issue is known as "Gregg's Paradox": if a single species is the only member of multiple hierarchical levels (for example, being the only species in its genus, which is the only genus in its family), then each level needs a distinct definition to maintain logical structure. Otherwise, the different taxonomic ranks become effectively identical, which creates problems for organizing biological diversity in a hierarchical o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
