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    The Ordovician Period

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    ORDOVICIAN PERIOD The Ordovician Period is the second period of the Paleozoic Era and began 485.4 million years ago and ended 443.4 million years ago (when the Silurian Period began). Four continents were present and separated by three main oceans. Laurentia was composed of present-day North America, part of Scotland, and Greenland and was near the equator. Siberia-Kazakhstan was east of Laurentia, slightly north of the equator. The Iapetus Ocean separated these two masses on the south from the

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    Essay On Horseshoe Crabs

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    probably think horseshoe crabs are crustaceans, but you’d be wrong. They actually aren’t crabs at all, and there’s more about the horseshoe crab that you wouldn’t believe. This weird-looking marine animal survived two mass extinctions and lived in the Ordovician Period. To begin with, the horseshoe crab, one the world’s oldest living creatures, are quite active. This fascinating crab has ten small walking legs under a strong, sturdy exoskeleton, a long spine in the abdomen, and a long pointy tail

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    Introduction: The Lophophore is a characteristic feeding organ possessed by four major groups of animals: the Brachiopod, Bryozoan, Entoprocts, and Phoronida, which collectively constituted the Lophophorata. [1] All Lophophore are found in aquatic organisms The Lophophore can most easily be described as a ring of tentacles, but is often horseshoe-shaped or coiled. Why do we call the tentacles a Lophophore? Because the tentacles have several distinctive characteristics that differentiate them from

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    rare occurrence of events proceeded the Triassic geologic periods and the Paleozoic and Mesozoic eras. This mass disaster was the largest dissipation of living life on planet earth; it is believed to be even superior to other crises such as the Ordovician and Devonian events and the conclusion of the cretaceous era that came upon the dinosaurs. The eradication of species numbers average at a toll close to one hundred percent of earths total living creatures. “It is the Earth's most severe known extinction

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    echinoderm Lagerstatte in the Upper Ordovician succession of the Craighead inlier in southwest Scotland called the Lady Burn Starfish Bed and the Lewiston Member of the Rochester Shale Lagerstätten. The Lady Burn Starfish beds are located in Scotland and were discovered by the paleontologist Elizabeth Gray (Donovan et al., 2002). This bed is comprised of at least three units known now as the Ashgillian and were deposited just before the first extinction in the Late Ordovician (Nudds & Selden 2008). The

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    the extinction of another and more dominant species to survive, thrive, and evolved with ease. Extinctions empty niches and let other species evolve and grow. Three examples of extinctions that led to the evolution of different species are the Ordovician Extinction and how it led to the Do At the

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    470 million years, from Ordovician sandstones to Pleistocene glacial till. The Ordovician St. Peter Formation sandstone was deposited across the midcontinent during the second major marine transgression of the Paleozoic Era. The first transgression deposited Upper Cambrian to Lower Ordovician clastics and carbonates. The clastic to carbonate rock transition is consistent with gradual sea level rise over the North American craton. Sea level dropped late in the early Ordovician, exposing the carbonate

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    At the first site in the Iowa River Valley near Belle Plain, Iowa, we would potentially encounter a Cambrian-Ordovician aquifer or Silurian-Devonian aquifer. The Cambrian-Ordovician aquifer consists of 460-500 Ma sandstones and dolomites. The aquifer is composed of water bearing bedrock units; Jordan Sandstone, Ordovician aged dolomite and sandstone and St. Peter Sandstone. The lateral extent and thickness of the units creates an artesian aquifer system. Well depths range from 300 to 2,000 feet below

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    Despite being only twenty-five miles apart, Mystery Cave and Niagara Cave are surprisingly different. One of the major differences between Niagara and Mystery Cave is that Mystery Cave has bats. Another difference is Mystery Cave is owned by the State of Minnesota, while Niagara Cave is privately owned. On the other hand, since the caves are located in southeastern Minnesota, they both are made of limestone, and ancient fossils are found in each of the caves. Mystery Cave is the only cave in Minnesota

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    End-Permian’s calculated species loss at 95%, the second-highest is the end of the Ordovician extinction with 85%. In the observed extinction of families, End-Permian reports an estimated 51%. The next highest estimate is End-Ordovician with 26%, and the End-Cretaceous which receives the lowest of 16%. The trend continues with the observed extinction of genera, with End-Permian at an estimated 82%, and End-Ordovician at 60%. In all of those metrics weighing biological loss, the P/T extinction is ahead

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