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Paleontology in Oregon refers to paleontological research occurring within or conducted by people from the U.S. state of Oregon. Oregon was probably submerged under seawater during the early Paleozoic era, but no rocks are known from the Cambrian to Silurian to verify this likelihood. From the Devonian to the Permian, an island chain formed in the state. Coral reefs formed in their vicinity and a rich flora greened the local terrestrial environments. Oregon remained mostly covered in seawater throughout the Mesozoic. Local wildlife would come to include marine invertebrates and ichthyosaurs. Terrestrial life included pterosaurs and dinosaurs. During the early Cenozoic era the state was still mostly covered in seawater, but local sea levels began to rise and fall. On land, the local forests would come to be inhabited by creatures like bear dogs, camels, cats, deer, gomphotheres, and horses. The local climate gradually cooled and a variety of habitats like forests, arid plains and savannahs. Relatives of modern elephants lived in the state. Local Native Americans devised myths to explain fossils. By the mid-19th century local fossils had come to the attention of formally trained scientists. Notable local finds include the John Day Fossil Beds, the only fossil crocodile known west of the Rockies, fossil bear footprints, and a plesiosaur skeleton. The Eocene dawn redwood ''Metasequoia occidentalis'' is the Oregon state fossil. ==Prehistory== No Precambrian fossils are known from Oregon, so the state's fossil record does not begin until the Paleozoic.〔 No rocks are known in Oregon from the Cambrian to the Silurian, although the state was probably submerged by the sea.〔 From the Devonian to the Permian a chain of volcanic islands began forming in the state. These islands were home to lagoons and surrounded by coral reefs. Brachiopods also inhabited the nearby waters. Plant fossils suggest a rich terrestrial flora was not far away.〔 Oregon remained mostly covered in seawater throughout the Mesozoic. Local marine invertebrate life included corals, oysters, and snails. Local vertebrates included ichthyosaurs and pterosaurs.〔 Although it has been claimed that no dinosaurs are known to have inhabited Oregon,〔 fossils of a possible hadrosaurid ("duck-billed" dinosaur) were discovered in the southwestern corner of the state, believed to be Campanian in age.〔Weishampel DB, ''et al''. (2004) "Dinosaur Distribution". The Dinosauria, eds Weishampel DB, Dodson P, Osmólska H. University of California Press, Berkeley, CA, Second Ed, pp 575–582.〕 During the Cretaceous period, between 90 and 100 million years ago, most of Oregon was covered by the ocean.〔 Plesiosaurs swam and fed on the fish of this Oregonian ocean.〔 Oregon remained partially covered by the sea into the Cenozoic. Contemporary marine life included fig and turret-shelled snails.〔 During the Tertiary, Oregon trees like ''Alniphyllum'', ash, beech, cinnamon, ''Gargura'', hemlock, hickory, hornbeam, oak, persimmon, pine, redwood, and sycamore grew in Oregon.〔 Alders were also present.〔 The most common local trees were the redwoods and sycamores.〔 The Tertiary petrified wood of Oregon is sometimes partially opalized.〔 Oregon's sea levels fluctuated rapidly during the Eocene to Oligocene interval.〔 Mollusks were diverse in Oregon during the Eocene, with at least 25 species known from the Fern Ridge Dam area.〔 From the Eocene to the Oligocene, the Sunset Highway area was covered in seawater. During this interval it was inhabited by invertebrates like crinoids, crustaceans, echinoderms, gastropods, and scaphopods.〔 Local Eocene sharks left their teeth behind in the Rocky Point Quarry to the west of the Nehalem River.〔 Crocodiles lived in Oregon from 60 to 45 million years ago.〔 The local flora from this interval also left behind remains that would later fossilize.〔 As the Cenozoic proceeded, the climate of Oregon became cooler and drier. Local marine life took on a more modern aspect. These were inhabited by creatures like bear dogs, camels, cats, deer, gomphotheres, and horses. Local mountain building added the Cascade and Coast ranges to the local topography.〔 Oligocene crinoids were preserved near Vernonia.〔 During the early Oligocene, Oregon's terrestrial environments were home to ''Cinnamomum'', cycads, palms, the primitive sycamore ''Platanophyllum angustilobus'', and walnuts. The plant fossil sites to the east of Clarno's Ferry are one of the few places in the world where the fruits, leaves, and wood, of prehistoric plants were preserved in a single location.〔 Late Oligocene fossil salamanders were preserved near north Goshen.〔 During the Oligocene and Miocene, volcanic eruption-emitted clouds of ash buried many animals.〔 During the Pleistocene, mountains developed icy caps. A variety of environments filled the flatter areas of the state. Among these were arid plains, forests, and savannahs. Volcanic eruptions occurred sporadically in the Cascade Mountains throughout the rest of the Cenozoic.〔 During the Pleistocene, relatives of modern elephants left behind teeth and fragmentary skeletal remains in the Spencer Creek area and other parts of the Willamette Valley.〔 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 Oregon」の詳細全文を読む スポンサード リンク
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