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Mammal Fossils

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| image = [[File:Short-Faced Bear Skull.jpeg]]
| caption = skull of short-faced bear
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<p>Mammals first appeared during the Triassic Period and lived with dinosaurs during the Mesozoic Era. At the beginning of the Cenozoic Era, after extinction of the dinosaurs about 65 million years ago, mammals flourished and diversified. However, similar to the Mesozoic Era, Ohio was an upland land mass and erosion removed large quantities of rock. It is probable that mammals roamed Ohio just as had the dinosaurs but no rocks, and therefore no mammal remains from the Paleogene and Neogene Periods are preserved in the state. It was not until the Pleistocene Ice Age that remains of mammals were entombed and preserved in sediments.</p>
<p>Most, if not all, mammal remains from Pleistocene sediments in Ohio represent the last part of the Ice Age (Wisconsinan) and many sites yield radiocarbon dates that place them very near the end of the Ice Age (10,000 years ago) when glacial ice had been gone from the state for several thousand years. Most of the fossil-bearing deposits represent former glacial lakes and ponds that are now swampy areas. Excavation of these deposits sometimes yields large bones that are easily recognized as unusual. Isolated teeth, tusks, and bones are commonly picked up along streams and rivers in sand and gravel deposited as out wash of from melting glaciers. These specimens are commonly broken and water worn. The best specimens and the greatest diversity are from deposits preserved in caves and sinkholes. Only one such deposit is known from Ohio, although they are abundant in other states with better development of caves.</p>