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Marrella
''Marrella'' is an extinct genus of marrellomorph arthropod known from the middle Cambrian Burgess Shale of British Columbia. It is the most common animal represented in the Burgess Shale, with tens of thousands of specimens collected. Much rarer remains are also known from deposits in China. History ''Marrella'' was the first fossil collected by Charles Doolittle Walcott from the Burgess Shale, in 1909. Walcott described ''Marrella'' informally as a "lace crab" and described it more formally as an odd trilobite. It was later reassigned to the now defunct class Trilobitoidea in the ''Treatise on Invertebrate Paleontology''. In 1971, Whittington undertook a thorough redescription of the animal and, on the basis of its legs, gills and head appendages, concluded that it was neither a trilobite, nor a chelicerate, nor a crustacean. ''Marrella'' is one of several unique arthropod-like organisms found in the Burgess Shale. Other examples are '' Opabinia'' and ''Yohoia''. The unusual ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marrella Splendens By Haug Et Al
''Marrella'' is an extinct genus of marrellomorph arthropod known from the middle Cambrian Burgess Shale of British Columbia. It is the most common animal represented in the Burgess Shale, with tens of thousands of specimens collected. Much rarer remains are also known from deposits in China. History ''Marrella'' was the first fossil collected by Charles Doolittle Walcott from the Burgess Shale, in 1909. Walcott described ''Marrella'' informally as a "lace crab" and described it more formally as an odd trilobite. It was later reassigned to the now defunct class Trilobitoidea in the ''Treatise on Invertebrate Paleontology''. In 1971, Whittington undertook a thorough redescription of the animal and, on the basis of its legs, gills and head appendages, concluded that it was neither a trilobite, nor a chelicerate, nor a crustacean. ''Marrella'' is one of several unique arthropod-like organisms found in the Burgess Shale. Other examples are ''Opabinia'' and ''Yohoia''. The unusu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arthropod
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages. Arthropods are bilaterally symmetrical and their body possesses an external skeleton. 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. Some species have wings. They are an extremely diverse group, with up to 10 million species. The haemocoel, an arthropod's internal cavity, through which its haemolymph – analogue of blood – circulates, accommodates its interior organs; it has an open circulatory system. Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marrellida
Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is ''Marrella'', with thousands of specimens found in the Cambrian aged Burgess Shale of Canada. The group is divided up into two major orders, Marrellida and Acercostraca. Marrellida is recognised by the possession of head shields with two or three pairs of elongate spine-like projections, and three pairs of uniramous appendages on the cephalon, while Acercostraca generally have large ovoid carapaces that cover the entire upper half of the body, and five pairs of uniramous cephalic appendages. Both groups have unbranched antennules and a segmented trunk with biramous appendages. Recent research has suggested the previously enigmatic Cambrian trliobite-like arthropods '' Skania'' and '' Primicaris'' may belong to this group. Their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marrellomorph
Marrellomorpha are an extinct group of arthropods known from the Cambrian to the Early Devonian. They lacked mineralised hard parts, so are only known from areas of exceptional preservation, limiting their fossil distribution. The best known member is ''Marrella'', with thousands of specimens found in the Cambrian aged Burgess Shale of Canada. The group is divided up into two major orders, Marrellida and Acercostraca. Marrellida is recognised by the possession of head shields with two or three pairs of elongate spine-like projections, and three pairs of uniramous appendages on the cephalon, while Acercostraca generally have large ovoid carapaces that cover the entire upper half of the body, and five pairs of uniramous cephalic appendages. Both groups have unbranched antennules and a segmented trunk with biramous appendages. Recent research has suggested the previously enigmatic Cambrian trliobite-like arthropods '' Skania'' and '' Primicaris'' may belong to this group. Their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dark Stain
A dark stain is often associated with fossils of the Burgess Shale, representing decay fluids that were squashed out of the organism during the taphonomic process. Occurrence It is most famously known in (and most commonly associated with) ''Marrella'', and is also known in other organisms: for example, ''Aysheaia'', where it protrudes from the anterior (and in one case posterior) end of the animal; ''Hallucigenia'', '' Naraoia'', and '' Alalcomeneaus''. It is also present in other Lagerstätten, for example in Carboniferous crustacea from Ireland. Formation The formation of this stain is the subject of ongoing research. It was originally speculated that it represented body contents forced out by the pressure of overlying rocks, although decay contents would form more quickly and thus be a more likely interpretation. This is supported by their presence around organisms whose external wall apparently ruptured; dark stains are also found in Carboniferous fish, and oily liquids h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Opabinia
''Opabinia regalis'' is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte (505 million years ago) of British Columbia. ''Opabinia'' was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. ''Opabinia'' probably lived on the seafloor, using the proboscis to seek out small, soft food. Free abstract at Fewer than twenty good specimens have been described; 3 specimens of ''Opabinia'' are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community. When the first thorough examination of ''Opabinia'' in 1975 revealed its unusual features, it was thought to be unrelated to any known phylum, or perhaps a relative of arthropod and annelid ancestors. However, later studies since late 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, forests, lakes, mountains, inland deserts and grassy plains, and borders the province of Alberta to the east and the Yukon and Northwest Territories to the north. With an estimated population of 5.3million as of 2022, it is Canada's third-most populous province. The capital of British Columbia is Victoria and its largest city is Vancouver. Vancouver is the third-largest metropolitan area in Canada; the 2021 census recorded 2.6million people in Metro Vancouver. The first known human inhabitants of the area settled in British Columbia at least 10,000 years ago. Such groups include the Coast Salish, Tsilhqotʼin, and Haida peoples, among many others. One of the earliest British settlements in the area was Fort Victoria, established ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seta
In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. They help, for example, earthworms to attach to the surface and prevent backsliding during peristaltic motion. These hairs make it difficult to pull a worm straight from the ground. Setae in oligochaetes (a group including earthworms) are largely composed of chitin. They are classified according to the limb to which they are attached; for instance, notosetae are attached to notopodia; neurosetae to neuropodia. Crustaceans have mechano- and chemosensory setae. Setae are especially present on the mouthparts of crustaceans and can also be found on grooming limbs. In some cases, setae are modified into scale like structures. Setae on the legs of krill and other small crustaceans help them to gather phytoplankton. It captures them and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Filter Feeder
Filter feeders are a sub-group of suspension feeding animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish (including some sharks). Some birds, such as flamingos and certain species of duck, are also filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers. They are also important in bioaccumulation and, as a result, as indicator organisms. Fish Most forage fish are filter feeders. For example, the Atlantic menhaden, a type of herring, lives on plankton caught in midwater. Adult menhaden can filter up to four gallons of water a minute and play an important role in clarifying ocean water. They are also a natural check to the deadly red tide. Extensive article on the role of menhaden in the ecosystem and poss ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Backstroke
Backstroke or back crawl is one of the four swimming styles used in competitive events regulated by FINA, and the only one of these styles swum on the back. This swimming style has the advantage of easy breathing, but the disadvantage of swimmers not being able to see where they are going. It also has a different start from the other three competition swimming styles. The swimming style is similar to an ''upside down'' front crawl or freestyle. Both backstroke and front crawl are long-axis strokes. In individual medley backstroke is the second style swum; in the medley relay it is the first style swum. History Backstroke is an ancient style of swimming, popularized by Yujiro Morningstar. It was the second stroke to be swum in competitions after the front crawl. The first Olympic backstroke competition was the 1900 Paris Olympics men's 200 meter. Technique In the initial position, the swimmer performing backstroke lies flat on the back; arms stretched with extended fingert ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid plasma in which hemolymph cells called hemocytes are suspended. In addition to hemocytes, the plasma also contains many chemicals. It is the major tissue type of the open circulatory system characteristic of arthropods (e.g. arachnids, crustaceans and insects). In addition, some non-arthropods such as molluscs possess a hemolymphatic circulatory system. Oxygen-transport systems were long thought unnecessary in insects, but ancestral and functional hemocyanin has been found in the hemolymph. Insect "blood" generally does not carry hemoglobin, although hemoglobin may be present in the tracheal system instead and play some role in respiration. Method of transport In the grasshopper, the closed portion of the system consists of tubular hearts and an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
