An independent researcher has asserted that a marble bust of Christ in a Roman church is by Michelangelo. It's the latest purported attribution to the Renaissance genius who is one of the most imitated artists in the world. The unverified claim by Valentina Salerno on Wednesday has unsettled Renaissance scholars, especially since a recent sketch of a foot, attributed to Michelangelo but disputed by some as a copy, recently fetched $27.2 million at auction. Salerno has published her initial claims online.