Who was the scientist that discovered the large brontosaurus?

The brontosaurus was my favorite dinosaur, so it came as a bit of a shock to me to learn that it really didn't exist. A fellow named O.C. Marsh found a skeleton of an already-named animal called "Apatosaurus," but it was missing its head. To make a better-looking display for the Peabody Museum, he fitted it with the head of another creature called "Camarasaurus" and named the resulting chimera "Brontosaurus."

Since Apatosaurus contributed most of the skeleton, many books identify the creature as "Apatosaurus, formerly called Brontosaurus" but that's not strictly correct.