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Paleontology in Delaware
Paleontology in Delaware refers to paleontological research occurring within or conducted by people from the U.S. state of Delaware. There are no local rocks of Precambrian, Paleozoic, Triassic, or Jurassic age, so Delaware's fossil record does not begin until the Cretaceous period. As the Early Cretaceous gave way to the Late Cretaceous, Delaware was being gradually submerged by the sea. Local marine life included cephalopods like ''Belemnitella americana'', and marine reptiles. The dwindling local terrestrial environments were home to a variety of plants, dinosaurs, and pterosaurs. Along with New Jersey, Delaware is one of the best sources of Late Cretaceous dinosaur fossils in the eastern United States.〔 Delaware was still mostly covered by sea water through the Cenozoic era. Local marine life included manatees, porpoises, seals, and whales. Delaware was worked over by glaciers during the Ice Age. The Cretaceous belemnite ''Belemnitella americana'' is the Delaware state fossil.
==Prehistory==
No fossils are known from the rocks of the Precambrian or Paleozoic of Delaware because the rocks are metamorphic in origin. Fossils are also locally absent from the Triassic and Jurassic period since there are no local rocks of these ages in which they might be preserved. However, Cretaceous rocks and fossils are known. During the transition between the Early and Late Cretaceous, Delaware was changing from a terrestrial environment to a shallow sea. A variety of local plants left behind abundant fossils in the state's contemporary terrestrial environments. Local animals included dinosaurs and pterosaurs.〔 Cretaceous invertebrates of Delaware included annelids, cephalopods, crustaceans, gastropods, and pelecypods.〔 One of the most common Cretaceous invertebrate species found in the state is the crab ''Callianassa mortoni'', whose claws are abundant in the Merchantville Formation.〔 Notable cephalopods of Cretaceous Delaware included the swift swimming belemnite ''Belemnitella americana''. Cretaceous trace fossils include the mysterious tube-like ''Halymenites major''.〔 Marine reptiles inhabited the sea that came to expand over the state.〔 Along with New Jersey, Delaware is one of the best sources of Late Cretaceous dinosaur fossils in the eastern United States.〔
Delaware continued to be largely covered by seawater during the Cenozoic era, although its level rose and fell over time. Local marine life included manatees, porpoises, seals, and whales. On land, the state was home to bears, beavers, dogs, and snakes.〔 About 17.5 million years ago, more than 100 kinds of mollusks lived in the waters off the Delaware coast. Local marine vertebrates included bony fishes, porpoises, rays, sea cows, sharks, sea turtles, and whales. Fossil pollen suggests that the state's Miocene coastal regions were less marshy than they are today. Local vegetation included forests composed of oaks, palms, and pines. The climate may have resembled that of modern Georgia's southern half. On land, the local inhabitants included beavers, a possible saber-toothed cat, chalicotheres, deer-like animals, rabbits, peccaries, hornless rhinoceroses, and small primitive horses.〔 Local Ice Age glacial activity made significant sedimentary deposits, but these preserved few fossils.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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