Back when you were a kid and you were first learning about dinosaurs - almost no matter what age you are today - you probably learned about a dinosaur named Brontosaurus. As one of the first dinosaurs to be reconstructed with fossil fragments and shown to the public as a quintessential "thunder lizard," Brontosaurus remained a popular name for a certain kind of long dinosaur for many years after it was formally retired. In 1903, paleontologist Elmer Riggs suggested that traits that separated the Brontosaurus and the Apatosaurus suggested that the former was just a shorter or younger version of the latter. This week that changes.
Yale paleontologist Othniel Charles Marsh named the Brontosaurus excelsus in 1879 in a paper called "Notice of New Jurassic Reptiles." In the year 1877, Marsh named a very similar genus called Apatosaurus ajax.