The Brontosaurus, whose name means "thunder lizard" in Greek, is one of the most famous dinosaurs of all. However, there is no dinosaur that is named Brontosaurus!
A long time ago Dr. O. C. Marsh discovered a small four legged dinosaur with a long neck. He decided to name the dinosaur Apatosaurus meaning deceptive lizard. Later the same scientist discovered a much bigger dinosaur of the same type. Because the back bones seemed different he decided it was a different dinosaur. This dinosaur was so big he decided to name it Brontosaurus. When scientists looked at these fossils later they realized that the Apatosaurus was the same animal as the Brontosaurus.