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Paleontology in Colorado refers to paleontological research occurring within or conducted by people from the U.S. state of Colorado. The geologic column of Colorado spans about one third of Earth's history. Fossils can be found almost everywhere in the state but are not evenly distributed among all the ages of the state's rocks.〔 During the early Paleozoic, Colorado was covered by a warm shallow sea that would come to be home to creatures like brachiopods, conodonts, ostracoderms, sharks and trilobites. This sea withdrew from the state between the Silurian and early Devonian leaving a gap in the local rock record. It returned during the Carboniferous. Areas of the state not submerged were richly vegetated and inhabited by amphibians who left behind footprints that would later fossilize. During the Permian the sea withdrew and alluvial fans and sand dunes spread across the state. Many trace fossils are known from these deposits. The sea returned during the Triassic, while exposed areas were a richly vegetated coastal plain that was home to dinosaurs. Colorado was again submerged by a sea during the Cretaceous period that was home to plesiosaurs up to 70 feet long. During the early part of the Cenozoic era, rainforests grew in Colorado. Later, another rich flora and fauna would come to be preserved in the Florissant beds, where both rhinoceroses and uintatheres lived. More recently the state's modern prairies began to form and the state was home to creatures like bison, camels, horses, and mammoths. Local Native Americans have devised myths to explain local fossil bones and dinosaur footprints. By the late 19th century, local fossils had attracted the attention of formally trainer scientists. Major finds include the Late Jurassic dinosaurs of the Morrison Formation and the Cenozoic plants and mammals of the Florissant beds. The Jurassic plated dinosaur ''Stegosaurus armatus'' is the Colorado state fossil. ''Stegosaurus'' is also the state dinosaur of Colorado. ==Prehistory== No Precambrian fossils are known from Colorado, so the state's fossil record does not begin until the Paleozoic.〔 At the start of the Paleozoic, Colorado was located near the equator. The state was submerged under a warm shallow sea.〔 At least part of Colorado was covered by shallow water during the Middle Ordovician. At the time, Colorado was home to invertebrates like articulated brachiopods, conodonts, gastropods, ostracods, pelecypods, sponges, trilobites, and worms (known from trace fossils). Contemporary vertebrates included armored jawless fish called ostracoderms.〔 Sometime between the Silurian and early Devonian the sea withdrew from the state. While the sea was gone local sediments were eroded away rather than deposited. During the Carboniferous the absent sea returned, although some areas of the state remained dry land. Brachiopods, crinoids, sharks, and trilobites inhabited the sea. A rich variety of plants grew in Colorado's terrestrial environments. Examples include ''Calamites'', conifers, and lycopods. Mountain ranges were being raised in the western part of the state by geologic forces.〔 During the Carboniferous, footprints were laid down in Colorado by early tetrapods that would later fossilize.〔 That being said, Colorado is not generally a good source of Carboniferous aged fossils.〔 Western Colorado had a series of alluvial fans during the Permian when the Cutler Group was being deposited. Preserved in these sediments are tracks referred to the ichnospecies ''Limnopus cutlerensis'', which may have been left by a temnospodyl amphibian.〔 During the Permian the sea withdrew once more from the state. In its place were fields of sand dunes. Tracks left by ancient insects and reptiles were preserved in these dune deposits.〔 Also like the Carboniferous, despite the presence of contemporary trace fossils, the fossil record of Permian life in Colorado is relatively poor compared to states like Kansas and Texas.〔 Seawater returned to Colorado during the ensuing Triassic period, although it left significant areas of the state uncovered.〔 These terrestrial areas included coastal floodplains vegetated by conifers and inhabited by creatures like amphibians and dinosaurs.〔 The Late Triassic also saw the formation of many footprints that would later fossilize. These are preserved in the sediments of the Chinle Formation of the northwestern part of the state.〔 A chicken to turkey sized theropod dinosaur left behind footprints of the ichnogenus ''Agialopous''. These tracks contain large number of the ichnogenus ''Rhynchosauroides'', which resembles lizard footprints. The Chinle of Colorado also bears the greatest known abundance of the ichnogenus ''Gwynnedichnium''.〔 Both Triassic amphibians and reptiles left behind footprints near what is now the Fall Creek Post Office.〔 During the Late Jurassic deposition of the sediments now known as the Morrison Formation, both sauropods and theropods left behind footprints.〔 Only two large tracksites of fossil footprints are known from the Morrison Formation and both of them are located in Colorado.〔 A tracksite called Rancho del Rio preserves both sauropod and theropod tracks. The Rancho del Rio site is located along the Colorado River in central Colorado. The other large tracksite is the Purgatoire Valley tracksite of the eponymous Purgatoire River in southeastern Colorado.〔 The Purgatoire Valley tracksite is 400 meters at its widest and contains four track-bearing strata. One of the four track bearing strata bears more than 1,300 individual prints.〔 A series of five parallel trackways left by young sauropods provides important evidence for dinosaur social behavior.〔 The trackways of young sauropods found at the Purgatoire Valley site fill important gaps in the local body fossil record, as the vast majority of sauropods skeletal remains in the Morrison come from grown individuals.〔 Much of Colorado was covered by an expanding sea during the ensuing Cretaceous period.〔 This sea is known as the Western Interior Seaway.〔 Algae, fish, molluscs, and marine reptiles inhabited its waters.〔 The mosasaur ''Platecarpus'' was one such marine reptile.〔 When the Graneros Shale was being deposited in Colorado, the plesiosaur ''Thalassomedon'' lived in the state.〔 This was a truly huge plesiosaur that could exceed 45 feet in length.〔 Beyond the shores of this sea were forests and swamps where early flowering plants grew. Later in the Cretaceous, the sea withdrew. Dinosaurs were still present, but the vegetation had undergone significant changes. The forests were now made of broadleafed trees and palms. At this point the local Rocky Mountains began to rise.〔 During the Cretaceous cephalopods with coiled shells and clams were preserved at Monument Creek.〔 Fish were present in Coloradan waters and left behind scales that would later fossilize. On land the flora also left behind leaves that would later fossilize.〔 The sediments of the Benton Formation preserved both invertebrates and marine reptiles.〔 The bivalve ''Ostrea congesta'' was preserved in the Colorado Niobrara Formation.〔 The Niobrara's vertebrate life included sharks, which left behind fossil teeth.〔 Colorado was home to bivalves and straight shelled cephalopods when the Pierre shale was being deposited.〔 The Pierre shale are mound-shaped bioherms up to 15 inches in diameter.〔 A sixty to seventy foot plesiosaur was preserved in what is now Baca County, which is in the southeastern region of the state.〔 Marine mollusks were preserved in the Fox Hills Formation.〔 Oysters and other mollusks were preserved in the sediments now composing the Dakota Formation. Aspects of the Coloradan flora were also preserved from this time. The most common plant fossils of the Dakota are the leaves of deciduous trees. Other contemporary plants included ferns and palms.〔 The uplift of the Rocky Mountains persisted into the early part of the Cenozoic era. They were surrounded by rainforests at this point in prehistory. Areas in the state with lower elevation became the sites of vast lakes. Fish, insects, and leaves would end up entombed in sediments deposited by these lakes.〔 After the start of the Cenozoic, early Paleocene turtles left behind fossils near modern Golden.〔 The Coloradan flora of the ensuing Eocene epoch left behind plant fossils like ferns, palm leaves, and petrified wood.〔 Animal life of northwestern Colorado during the Eocene included the primitive horse ''Eohippus'', early titanotheres, and uintatheres.〔 A rich flora grew in Colorado during the Oligocene. At least 150 different kinds of plants from this epoch are preserved in what is now the Florissant beds of Colorado. Among the members of this flora were sequoia trees with trunks up to 17 and a half feet in diameter. More than a thousand different kinds of insect have been documented among the same beds.〔 Beetles were among the Florissant insects.〔 A diverse mammalian fauna inhabited this ancient forest.〔 Members included animals resembling giant pigs, rhinoceroses, and titanotheres. During the Pliocene, Colorado was home to creatures like rhinoceroses and giant pig-like animals. The state's modern prairies formed during the Quaternary.〔 Colorado was shaken by volcanic eruptions. The state's climate gradually cooled as the Cenozoic proceeded. The rainforests gave way to ''sequoia'' forests and grasslands.〔 Pleistocene Colorado had a diverse mammal fauna. Among them were ''Archidiskodon'', a relative of modern elephants.〔 Bison, camels, horses, and mammoths also inhabited the state at this time.〔 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 Colorado」の詳細全文を読む スポンサード リンク
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