In the case of the Peabody Museums's Brontosaurus, the exhibitors actually lost their head. That is, to say, they now realize that the skull they put on it doesn't belong to the species at all. Unfortunately, they do not have the right skull to complete the skeleton, so the one on view is admittedly wrong, as you can see from the explanations posted here:
But, wait, there's more! What you thought of a Brontosaurus might, in fact, be an Apatosaurus. With respect to the identification, what had been proposed back in the 1870s proved to be more correct than what was said in 1903, as was proven by a study as late as 2015!
This what I believe Richard Feynman meant in his often quoted, "Science is the belief in the ignorance of the experts." Science can only advance if people do not accept previously established theories as axiomatic but continue to test and experiment. The job of the true scientist is not to make the data fit the theory that corresponds to a particular agenda but to make the theory fit the data.