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Paleontology in Nebraska refers to paleontological research occurring within or conducted by people from the U.S. state of Nebraska. Nebraska is world famous as a source of fossils.〔 During the early Paleozoic, Nebraska was covered by a shallow sea that was probably home to creatures like brachiopods, corals, and trilobites. During the Carboniferous, a swampy system of river deltas expanded westward across the state. During the Permian period, the state continued to be mostly dry land. The Triassic and Jurassic are missing from the local rock record, but evidence suggests that during the Cretaceous the state was covered by the Western Interior Seaway, where ammonites, fish, sea turtles, and plesiosaurs swam. The coasts of this sea were home to flowers and dinosaurs. During the early Cenozoic, the sea withdrew and the state was home to mammals like camels and rhinoceros. Ice Age Nebraska was subject to glacial activity and home to creatures like the giant bear ''Arctodus'', horses, mammoths, mastodon, shovel-tusked proboscideans, and Saber-toothed cats. Local Native Americans devised mythical explanations for fossils like attributing them to water monsters killed by their enemies, the thunderbirds. After formally trained scientists began investigating local fossils, major finds like the Agate Springs mammal bone beds occurred. The Pleistocene mammoths ''Mammuthus primigenius'', ''Mammuthus columbi'', and ''Mammuthus imperator'' are the Nebraska state fossils. ==Prehistory== No Precambrian fossils are known from Nebraska, and the state's fossil record begins in the Paleozoic. From the Cambrian through the Devonian, Nebraska was covered by a shallow sea. None of the rocks deposited in this environment are exposed at the surface, so its fossil record is poorly known. Nevertheless, the fossil record of nearby states suggests that Nebraska was probably home to brachiopods, corals, and trilobites.〔 During the Carboniferous, the sea retreated westward and was replaced by large swamps growing in river deltas.〔 During the Carboniferous Period, local invertebrates included cephalopods, coral, crinoids and fusulinids. On land, the local flora also left behind fossils.〔 During the Permian, most of Nebraska was a terrestrial environment, but both brackish and freshwater habitats were present. The latter were home to aquatic plants, amphibians, and fishes.〔 From the Triassic to Jurassic, Nebraskan sediments were being eroded rather than deposited.〔 The Cretaceous Dakota Formation of the eastern part of the state preserved fossils of local dinosaurs.〔 Later in the Cretaceous, Nebraska was covered by seawater.〔 This sea was called the Western Interior Seaway.〔 Ammonites, fish, sea turtles, and plesiosaurs swam in these waters.〔 The plesiosaurs could reach lengths of up to forty feet.〔 The Cretaceous sharks of Nebraska were very similar to their contemporaries in neighboring Kansas.〔 On land, flowering plants were becoming abundant and the state's coastal plains were home to dinosaurs.〔 The Western Interior Seaway was gone from Nebraska by the early portion of the Cenozoic. It was replaced by a terrestrial environment dotted with lakes and rivers. The contemporary local wildlife were similar to modern forms. On occasion during the Cenozoic, volcanic activity in the Rocky Mountains covered regions of the state in ash.〔 Rhinoceroses first appeared in Nebraska during the Eocene epoch. They would continue to thrive on the plains for the next 35 million years. In fact, more Tertiary-aged rhinoceros remains have been found in Nebraska than any other state.〔 Rhinoceroses remained and were a prominent member of Oligocene Nebraska's fauna. Camels were a new arrival to Nebraska during the Oligocene. The earliest known example was ''Poebrotherium''.〔 The Oligocene wildlife of Scotts Bluff National Monument left behind footprints that would later fossilize in the sediments of the Arikaree beds. This is one of only seven known Oligocene fossil tracksites in the western United States.〔 About 25 million years ago a stream ran roughly parallel to the modern course of the Niobrara River.〔 During the Miocene, Nebraska was likely home to massive herds of the small rhinoceras ''Diceratherium cooki''. It composed about one quarter of the remains in the Miocene Agate Springs beds. Other Agate Springs fossils included bears, the pig-like ''Dinohyus'', horses, the chimerical looking perissodactyl ''Moropus'', rhinos, and tapirs.〔 Later in the Miocene, Nebraska was home to the rhino ''Teleoceras''.〔 During the middle Pliocene. Nebraska was home to ''Aphelops'' and ''Diceratherium'', the latter being preserved in Banner County. Roughly 70% of Nebraska's large mammals went extinct during a major extinction episode late in the Pliocene.〔 During the ensuing Pleistocene, glaciers deposited sediments responsible for preserving local life forms.〔 Early in the ensuing Pleistocene epoch, Nebraska was home to ''Giganticamelus fricki'' a gigantic camel more than eleven feet tall. Large mammalian wildlife thrived generally in Nebraska during the Ice Age. Ice Age wildlife of Nebraska included the giant bear ''Arctodus'', horses, jaguars, mammoths, mastodons, shovel-tusked proboscideans, saber-toothed cats, and tapirs. The largest Nebraskan ''Arctodus'' specimens have come from Sheridan and Cass Counties. Mastdon and mammoth fossils have been found in all 93 counties of Nebraska.〔 Wooly mammoth remains were preserved most abundantly in the western half of the state in areas like Dawes and Sioux Counties.〔 Post-Kansan glaciation Nebraska was home to bear, giant bears, giant bison, caribou, wild cats, wild cattle, cougars, deer, jaguars, true moose, animals resembling musk oxen, actual musk oxen, mountain sheep, and giant stag-moose. ''Archidiskodon imperator maibeni'' left remains in Lincoln County. ''Platycerabos dodsoni'' was a wild cow known from Cass County.〔 Other Late Pleistocene mammals included ''Ambelodon fricki'', extinct bison species, modern bison, modern coyotes, and a saber-toothed cat unrelated to ''Smilodon''.〔 The camel ''Camelops'' appeared during the later Pleistocene.〔 Some Nebraskan fossil-bearing deposits of Late Pleistocene age preserve animal remains associated with humans.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Paleontology in Nebraska」の詳細全文を読む スポンサード リンク
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