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Whether they're the skeleton of a dinosaur or the now stony remains of a tree that lived long ago, fossils can transport us back through the eons, giving us a window into world of the ancient Earth.
Oct. 12 is National Fossil Day in the United States, and many museums and national parks are taking part with special activities and by showing off their fossil collections. Of the nearly 400 national parks and monuments under the National Park Service, some 232 have known fossil resources. Here, we take a look at a few particularly notable fossil hotspots.