Cleaning sandstone from the fossilized leg bone of a 70-million-year-old dinosaur are, from left, junior Mehdi Joseph-Ouni, lecturer John J. Chiment and freshman Andrew Vidulich, another student in the Geology 106 class "Vertebrate Fossil Preparation." CAT scans taken before cleaning tell students what to expect inside the stone and protective covering, which was applied when the fossil was discovered in 1917 in Canada. The fossil from a centrosaurusm is on loan from the American Museum of Natural History and will be displayed in Snee Hall and at the Paleontological Research Institution in Ithaca before its return to the museum. Charles Harrington/University Photography