The first two of these expressions are widely used, but different from is preferred by careful, educated writers and speakers: "This specimen is different from (not than) that." Unfortunately, but correctly, different from often leads to extra words because than is a convenient shortcut for from that which. Even so, say different from rather than different than until widespread usage sanctions the latter term. Different to appears more often in British than in American usage.
Dictionary of problem words and expressions. Harry Shaw. 1975.