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Paleontology in Ohio refers to paleontological research occurring within or conducted by people from the U.S. state of Ohio. Ohio is well known for having a great quantity and diversity of fossils preserved in its rocks. The state's fossil record begins early in the Paleozoic era, during the Cambrian period. Ohio was generally covered by seawater from that time on through the rest of the early Paleozoic. Local invertebrates included brachiopods, cephalopods, coral, graptolites, and trilobites. Vertebrates included bony fishes and sharks. The first land plants in the state grew during the Devonian. During the Carboniferous, Ohio became a more terrestrial environment with an increased diversity of plants that formed expansive swampy deltas. Amphibians and reptiles began to inhabit the state at this time, and remained present into the ensuing Permian. A gap in the local rock record spans from this point until the start of the Pleistocene. During the Ice Age, Ohio was home to giant beavers, humans, mammoths, and mastodons. Paleo-Indians collected fossils that were later incorporated into their mounds. Ohio has been the birthplace of many world famous paleontologists, like Charles Schuchert. Many significant fossils curated by museums in Europe and the United States were found in Ohio.〔 Major local fossil discoveries include the 1965 discovery of more than 50,000 Devonian fish fossils in Cuyahoga County. The Ordovician trilobite ''Isotelus maximus'' is the Ohio state fossil. ==Prehistory== No Precambrian fossils are known from Ohio, so the state's fossils record does not start until the Cambrian Period.〔 During the later part of the period, Ohio was covered in seawater and located 10 degrees south of the equator. By the end of the Cambrian the sea was shallow and the climate dry. Although marine life was diverse during the Cambrian little is known about Ohio's Cambrian inhabitants because the only specimens known were found in core samples.〔 During the Ordovician Ohio was covered in a warm shallow sea that was deepest in the eastern half of the state. The environment was reminiscent of the modern Bahamas. Ohio was twenty degrees south of the equator at the time. Islands sometimes rose above sea level in western Ohio. Later on during the Ordovician the sea got deeper and spread across the state's entirety, but the seas gradually withdrew. Bryozoans are common Ohio fossils of Ordovician age. Others include brachiopods, cephalopods, trilobites, horn corals, snails, clams, echinoderms, and graptolites.〔 Ohio was dry land during the early Silurian. Later warm shallow seas returned to Ohio. Ohio was 20 degrees south of the equator. The seas got deeper in the middle Silurian.〔 The northern and eastern areas of the state were inundated by deeper waters than the rest of the state. Between the two depths a reef system composed of corals and sponges formed. The state was also home to brachiopods and echinoderms,〔 During the late Silurian the seas got shallower again. Other fossils included echinoderms, clams, brachiopods, and cephalopods.〔 During the early Devonian only eastern Ohio was still covered by the sea. Ohio was located near the equator. Brachiopods and echinoderms still remained in the area during the Early Devonian.〔 By the middle Devonian the seas had expanded across the state once more. Sharks and bony fishes appeared in the Middle Devonian. True land plants also appeared around this time. As the Devonian passed on the sea's circulation weakened and its oxygen levels dropped, leading to a state described as the "'stinking seas'".〔 Few organisms lived in these low oxygen conditions.〔 Nevertheless, overall Devonian Ohio had a rich fauna including coral reefs, bryozoans, brachiopods, trilobites, cephalopods, clams, crinoids, ostracodes.〔 The rock record of the early Mississippian in Ohio demonstrates the presence of deltas and bodies of flowing water. During the late Mississippian Ohio was covered by a shallow sea. Near the end of the Mississippian the seas withdrew from the state. Ohio was located near the equator. The fossil record of Ohio includes greater numbers of land plants, brachiopods, clams, crinoids, fishes.〔 Ohio was a low-lying swampy plain near the coast during the Pennsylvanian. Its latitude was near the equator. Sea levels rose and fell sporadically so the rock record shows a history of land, freshwater, and sea deposits. Fossils of land plants are common in Ohio's Pennsylvanian rocks. Amphibians, reptiles, and freshwater clam fossils are also known from the time. The marine life of Ohio included crinoids, snails, cephalopods, brachiopods, and fishes. Trilobites were also present, but their fossils are rare.〔 By the Permian period the sea had left completely. Local bodies of water were then lakes and rivers rather than saltwater.〔 Southeastern Ohio was a swamp-covered coastal plain.〔 Ferns and horsetails were among the state's rich flora.〔 Ohio was only about 5 degrees north of the equator. Sand and mud deposited on local river deltas gradually filled in the swamp. Later in the Permian Ohio was subjected to geologic uplift and its sediments were eroded away. Permian fossils aren't especially common in Ohio, but include snails, clams, fishes, plants, amphibians, and reptiles. Marine fossils from this period are rare.〔 From about 248 to 1.6 million years ago Ohio was above sea level, so its rocks were eroded away rather than deposited. Dinosaurs probably lived in Ohio but there is no fossil record of their presence.〔 The ensuing Tertiary period of the Cenozoic era is also missing from the local rock record.〔 However, during the Quaternary period Ohio was worked over by glacial activity. A mile thick glacier was position over the area now occupied by Cleveland during the early part of this period.〔 About two thirds of Ohio was covered by such glaciers. Entire Pleistocene forests buried by the action of glaciers have been discovered in Ohio.〔 Around this time Ohio was inhabited by giant beavers, mammoths, mastodons, ground sloths and more modern animals, including 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 Ohio」の詳細全文を読む スポンサード リンク
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