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The South Dakota Badlands
Badlands are a landscape where sparse vegetation and heavy rain have eroded soft layers into sharp ridges and gullies, leaving the rock exposed. The White River Group was the first American fossil locality to be systematically described, from the 1840s, and it established mammal palaeontology as a discipline in the United States. The beds span the Eocene–Oligocene transition, when the continental interior turned markedly cooler and drier — a shift that is the necessary background to grasslands and grazing animals later taking over the continent's interior.
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