The Quarry Exhibit Hall at Dinosaur National Monument in Utah is home to a large wall containing more than 1,500 fossils. Some of the species that may be spotted are the Allosaurus, Apatosaurus, Camarasaurus, Diplodocus, and Stegosaurus. But the bones on this wall weren’t arranged by any curator or paleontologist—they were deposited by an ancient stream more than 150 million years ago. In 1909, paleontologist Earl Douglass uncovered eight segments of a large dinosaur tail at the top of a steep sandstone cliff in Utah. This discovery—which turned out to be tail segments…
