Marsh spent his entire career at Yale University (1866–99) as the first professor of vertebrate paleontology in the United States. In 1870 he organized the first Yale Scientific Expedition, which explored the Pliocene (5.3 to 1.8 million years ago) deposits of Nebraska and the Miocene (23.8 to 5.3 million years ago) deposits of northern Colorado. Marsh continued to sponsor similar parties nearly every year thereafter until his death. In 1871 his party discovered the first pterodactyl (a flying reptile) found in the United States. In 1882 he was placed in charge of the U.S. Geological Survey's work in vertebrate paleontology, aggravating a fierce rivalry that existed between him and the American paleontologist Edward Cope (Cope, Edward Drinker). Credited with the discovery of more than a thousand fossil vertebrates and the description of at least 500 more, Marsh published major works on toothed birds, gigantic horned mammals, and North American dinosaurs. He also wrote Fossil Horses in America (1874) and Introduction and Succession of Vertebrate Life in America (1877). Marsh garnered national attention in the late 1860s when he revealed that the alleged remains of a prehistoric man (known as the Cardiff Giant) were fake.