Brontosaurus, as a valid genus

Cause of death

Killed by a successor

Elmer Riggs concluded it was the same animal as the earlier-named Apatosaurus, and the older name wins.

Brontosaurus was named in 1879 and demoted twenty-four years later when Elmer Riggs decided the specimen belonged to a genus already named Apatosaurus. Under the rules of zoological nomenclature the earlier name takes priority, so the better name lost on a technicality. It stayed officially dead for 112 years while remaining completely alive in public usage, and a 2015 reanalysis reinstated it as a separate genus after all.