When they first found 'brontosaurus' they couldn't find the skull. There was intense competition among museums, and pressure to get large specimens on display, so they stuck on a skull that was found nearby. It turned out to be the wrong one. (Camarasaurus, IIRC)
A few scientists think that, under the protocols for such things, brontosaurus is still the legitimate name for the critter. Stephen Jay Gould wrote an essay about it, called 'Bully for Brontosaurus'.