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Paleontology in Alaska refers to paleontological research occurring within or conducted by people from the U.S. state of Alaska. During the Late Precambrian, Alaska was covered by a shallow sea that was home to stromatolite-forming bacteria. Alaska remained submerged into the Paleozoic era and the sea came to be home to creatures including ammonites, brachiopods, and reef-forming corals. An island chain formed in the eastern part of the state. Alaska remained covered in seawater during the Triassic and Jurassic. Local wildlife included ammonites, belemnites, bony fish and ichthyosaurs. Alaska was a more terrestrial environment during the Cretaceous, with a rich flora and dinosaur fauna. During the early Cenozoic, Alaska had a subtropical environment. The local seas continued to drop until a land bridge connected the state with Asia. Early humans crossed this bridge and remains of contemporary local wildlife such as woolly mammoths often show signs of having been butchered. More recent Native Americans interpreted local fossils through a mythological lens. The local fossils had attracted the attention of formally trained scientists by the 1830s. Major local finds include the Kikak-Tegoseak ''Pachyrhinosaurus'' bonebed. The Pleistocene-aged wooly mammoth, ''Mammuthus primigenius'' is the Alaska state fossil. ==Prehistory== During the Late Precambrian, Alaska was covered by a shallow sea. This sea was home to bacteria and stromatolites that would later fossilize. Most of the state continued to be submerged by the sea. By this time Alaska was home to brachiopods and trilobites. During the ensuing Ordovician and Silurian a chain of volcanic islands occupied what is now the eastern part of the state. These islands originated as a result of contemporary local tectonism. Coral reefs formed in the seas around these islands. The northern third of Alaska was still covered by seawater from the Devonian to the Permian. Local marine life included ammonites, brachiopods, corals, and gastropods.〔 At least 34 different species of gastropods lived in Alaska during the late Paleozoic. Of these, 9 were completely new to science when first discovered.〔 During the Triassic, the sea expanded. Northern Alaska was submerged under deep water. Southern Alaska was under a shallow sea. The state's Triassic sea was home to bony fish, ichthyosaurs, and mollusca. Volcanic episodes happened frequently in the state at this time.〔 Volcanism continued into the Jurassic as Alaska experienced a period of relative geologic upheaval. Areas of the state remained inundated by the sea. This sea was home to ammonites and crinoids.〔 In the middle Jurassic most of the mountain ranges characterizing modern Alaska began to form.〔 Alaska's Middle Jurassic Callovian deposits are part of a large geologic region spreading down through Canada and even into the Lower 48 states including Montana, Idaho, North Dakota, Utah and New Mexico.〔 From the mid to late Jurassic, the area now occupied by Snug Harbor was home to a great diversity of marine invertebrates, which left behind a plethora of fossils. Among these were ammonites.〔 Others include belemnites, the gastropod ''Amberlya'', the pelecypods ''Lima'', ''Oxytoma'', and possibly ''Astarte'' and ''Isocyprina''.〔 Cretaceous Alaska gained additional landmass due to collisions with other tectonic plates. Local mountain building resulted in the formation of the Brooks Range and other topographic features. Some areas of Alaska were covered by the sea and others were dry land.〔 There were at least 5 species of ''Inoceramus'' in Alaska during the Cretaceous period. This was a widespread genus in Alaska and its fossil remains have been discovered in hundreds of different places.〔 Other Cretaceous shellfish were preserved at what is now Umiat Mountain.〔 More than 235 species of plants are known to have grown in Alaska during the Cretaceous, most of which were cycads.〔 Their remains are scattered across hundreds of sites. Among the finds were algae, ''Ampelopsis'', conifers, elm, ''Ficus'', a great diversity of hepaticae, laurel, magnolia, oaks, ''Pinus'', ''Platanus'', and sequoias. Invertebrate remains were also found with the plants.〔 Pieces of Cretaceous amber have been found on the shore of Nelson Island, which is located in the Bering Sea.〔 Dinosaurs lived in Alaska during the Cretaceous.〔 Alaska remained tectonically active into the Cenozoic era. Volcanism produced the Aleutian Islands.〔 During the Eocene, Alaska's plants resembled those today growing in the temperate, subtropical and tropical regions of earth today. Their remains were preserved in locations such as the Alaska Peninsula, Awik, the Cook Inlet's shoreline, Eagle City, Unga Island.〔 Alaska's late Miocene fossil record also documents the state's ancient invertebrates.〔 From the Miocene to the Pliocene, Alaska's land area just about reached its full modern extent.〔 Alaska's late Pliocene fossils record also documents the state's invertebrates of that age.〔 During periods of low sea level a land bridge connected Alaska and Asia, allowing an exchanged of the continents' wildlife. Significant areas of Alaska were covered by glaciers during the Quaternary. Alaska was also the site of continued volcanic activity.〔 In Alaska, Pleistocene mammal remains are often associated with artifacts left by Folsom people.〔 Geologically recent invertebrate fossils are also known from Alaska.〔 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 Alaska」の詳細全文を読む スポンサード リンク
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