published a study that described a well-preserved skeleton of a diplodocid from the Grand River Valley near Fruita, Colorado, Field Museum of Natural History specimen P25112. Riggs thought that the deposits were similar in age to those of the Como Bluff in Wyoming from which Marsh had described Brontosaurus. Most of the skeleton was found, and after comparison with both Brontosaurus and Apatosaurus ajax, Riggs realized that the holotype of A.ajax was immature, and thus the features distinguishing the genera were not valid. Since Apatosaurus was the earlier name, Brontosaurus should be considered a junior synonym of Apatosaurus. Because of this, Riggs recombined Brontosaurus excelsus as Apatosaurus excelsus. Based on comparisons with other species proposed to belong to Apatosaurus, Riggs also determined that the Field Columbian Museum specimen was likely most similar to A.excelsus. Despite Riggs' publication, Henry Fairfield Osborn, who was a strong opponent of Marsh and his taxa, labeled the Apatosaurus mount of the American Museum of Natural History Brontosaurus. Because of this decision the name Brontosaurus was commonly used outside of scientific literature for what Riggs considered Apatosaurus, and the museum's popularity meant that Brontosaurus became one of the best known dinosaurs, even though it was invalid throughout nearly all of the 20th and early 21st centuries. It was not until 1909 that an Apatosaurus skull was found during the first expedition, led by Earl Douglass, to what would become known as the Carnegie Quarry at Dinosaur National Monument. The skull was found a short distance from a skeleton (specimen CM3018) identified as the new species Apatosaurus louisae, named after Louise Carnegie, wife of Andrew Carnegie, who funded field research to find complete dinosaur skeletons in the American West. The skull was designated CM11162; it was very similar to the skull of Diplodocus. Another smaller skeleton of A.louisae was found nearby CM11162 and CM3018. The skull was accepted as belonging to the Apatosaurus specimen by Douglass and Carnegie Museum director William H. Holland, although other scientistsmost notably Osbornrejected this identification. Holland defended his view in 1914 in an address to the Paleontological Society of America, yet he left the Carnegie Museum mount headless. While some thought Holland was attempting to avoid conflict with Osborn, others suspected Holland was waiting until an articulated skull and neck were found to confirm the association of the skull and skeleton. After Holland's death in 1934, museum staff placed a cast of