Paleontology in South Dakota
[1]: 254–255 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.
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-toothed cat, and titanotheres.
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.
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.
As the sea retreated, South Dakota became a terrestrial environment dotted with lakes, streams, and swamps.
[1]: 256 During the Late Cretaceous, the region now occupied by the Black Hills of South Dakota may have attracted long-necked plesiosaurs from hundreds of miles away as a source of gastroliths.
[4]: 129 More shark species are known from the Cretaceous Western Interior Seaway deposits of South Dakota than other states, with rocks from the same environment like those of Kansas.
[1]: 256 The local mammals included three-toed horses, pig-like animals, the camel Poebrotherium, Protoceras, rhinoceroses, rodents, saber-toothed cats, tapirs, and titanotheres.
[1]: 256–257 At the time, South Dakota consisted of plains dotted with marshes and shallow lakes and split by wide streams.
As they melted, they deposited sediments that would preserve the fossil remains of creatures like bison, horses, mammoths, and mastodons.
This portrayal of the thunderbirds may have been influenced by associations of fossils of the Cretaceous pterosaur Pteranodon with marine reptiles of the same age in the western United States.
The Blackfeet engaged in regular trade with the Cliff Dweller and Navajo peoples of the southwest, which may explain how the fossil ended up so far from its place of origin.
[11]: 165–166 On September 10, 1804, four members of the Lewis and Clark Expedition recorded in their journals a fossil discovery along the banks of the Missouri River in what is now Gregory County in south-central South Dakota.
The men interpreted the remains as originating from a giant fish, but today scientists think the specimen was probably a mosasaur or plesiosaur.
[12]: 15 In 1847, Hiram A. Prout published a description of a fragmentary titanothere jaw discovered in the White River Badlands in the American Journal of Science.
Not long afterward, Joseph Leidy described the Oligocene camel Poebrotherium, which was discovered in the same general region as Prout's titanothere jaw.
The Tertiary deposits of the White River Badlands was active for decades and still ongoing in 1920 when the South Dakota School of Mines published its "Bulletin No.
[1]: 255 In 1877, the United States Geological Survey published a report on the ancient plants and invertebrates of South Dakota.
[1]: 255–256 In 1895, George Wieland discovered YPM 3000, the nearly complete and articulated type specimen of the giant sea turtle now known as Archelon ischyros, which had been preserved in the Pierre Shale.
The discovery was the likely instigator for Wieland's subsequent research into Late Cretaceous sea turtles that began the next year.
Among the creatures discovered were rhinoceroses, saber-toothed cats, giant pig-like animals, Protoceros, tapirs, horses and more.
