Dinosaur Hall at Carnegie Museum of Natural History has eleven different species of dinosaur on display. Stegosaurus is just one of the fascinating fossil animals you will see at Carnegie Museum of Natural History, the "Home of the Dinosaurs." Stegosaurus The bones of the Stegosaurus skeleton on display in Dinosaur Hall come from more than one Stegosaurus. Often scientists cannot find all the bones from one dinosaur, so they use bones from different animals to build a single skeleton. Sometimes they never find all the bones that belong in a skeleton, so they have to guess what some parts of the animal looked like. Our skeleton is made up of several Stegosaurus skeletons from the Morrison Formation. This formation of rocks, named after a town in Colorado, is 140 million years old and contains many fossilized dinosaur bones. These bones were found in coarse sandstone that was once sand in an ancient river that flowed when the dinosaurs were living there—long before the mountains now in that area existed. A museum paleontologist, Earl Douglass, found the Stegosaurus bones in 1915, and the skeleton was put on exhibit in 1940. At that time, scientists had to guess what Stegosaurus' hind feet looked like because they did not have a complete set of bones. Since then, scientists at Carnegie Museum of Natural History have found a complete hind foot of Stegosaurus. We now know that Stegosaurus had three large toes and a fourth one that could barely be seen.