Joseph Leidy (1823-1891) was a US anatomist/paleontologist who named the first dinosaurs found in the U.S.A. He excavated the first American dinosaur, Hadrosaurus, in 1858. Leidy named Antrodemus (1870, perhaps Allosaurus), Aublysodon (1868), Deinodon (1856), Diplotomodon (1868), Hadrosaurus (the first nearly-complete dinosaur skeleton and first-known duck-billed dinosaur, 1858), Palaeoscincus (1856), Thespesius (1856), Trachodon (1856), and Troodon (1856). Leidy was also the first scientist to identify many extinct species of camels, horses, sloths, tigers, and rhinoceroses.