Paleontology in South Dakota  Paleontology in South Dakota refers to paleontological research occurring within or conducted by people from the U.S. state of South Dakota. South Dakota is an excellent source of fossils as finds have been widespread throughout the state. During the early Paleozoic era South Dakota was submerged by a shallow sea that would come to be home to creatures like brachiopods, cephalopods, corals, and ostracoderms. Local sea levels rose and fall during the Carboniferous and the sea left completely during the Permian. During the Triassic, the state became a coastal plain, but by the Jurassic it was under a sea where ammonites lived. Cretaceous South Dakota was also covered by a sea that was home to mosasaurs. The sea remained in place after the start of the Cenozoic before giving way to a terrestrial mammal fauna including the camel "Poebrotherium", three-toed horses, rhinoceroses, saber teeth, and titanotheres. During the Ice Age glaciers entered the state, which was home to mammoths and mastodons. Local Native Americans interpreted fossils as the remains of the water monster Unktehi and used bits of "Baculites" shells in magic rituals to summon buffalo herds. Local fossils came to the attention of formally trained scientists with the Lewis and Clark expedition. The Cretaceous horned dinosaur "Triceratops horridus" is the South Dakota state fossil. No Precambrian fossils are known from South Dakota, so the state's fossil record does not begin until the Paleozoic. At the start of the Paleozoic South Dakota was submerged by a sea. The state's Cambrian life left behind a rich trace fossil record. Paleozoic marine life of South Dakota included brachiopods, cephalopods, and corals. The sea temporarily withdrew from South Dakota during the Ordovician period. But, in the middle or late Ordovician, ostracoderms swam over South Dakota. Similar ostracoderms were preserved near Canon City, Colorado. Later, during the Carboniferous period, sea levels again began to rise and fall. Marine life from this time included brachiopods and corals, but the rock record preserves evidence for local brackish and freshwater environments as well. The sea withdrew from the state altogether during the Permian and local sediments began being eroded rather than deposited.