The holotype, YPM 1876, was found in a layer of the Upper Brushy Basin Member of the Morrison Formation, dating from the Tithonian. It consists of a partial skeleton including a rather complete skull and lower jaws. Several other fossils from Wyoming have been referred to "Dryosaurus altus". They include specimens YPM 1884: the rear half of a skeleton; AMNH 834: a partial skeleton lacking the skull from the "Bone Cabin Quarry"; and CM 1949: a rear half of a skeleton dug up in 1905 by William H. Utterback. From 1922 onwards in Utah, Earl Douglass discovered "Dryosaurus" remains at the "Dinosaur National Monument". These include CM 11340: the front half of a skeleton of a very young individual; CM 3392: a skeleton with skull but lacking the tail; CM 11337: a fragmentary skeleton of a juvenile; and DNM 1016: a left ilium dug up by technician Jim Adams. Other fossils were found in Colorado. In Lily Park, Moffat County, James Leroy Kay and Albert C. Lloyd in 1955 recovered CM 21786, a skeleton lacking skull and neck. From 'Scheetz’ Quarry 1, at Uravan, Montrose County, in 1973 Peter Malcolm Galton and James Alvin Jensen described specimen BYU ESM-171R found by Rodney Dwayne Scheetz and consisting of some vertebrae, a left lower jaw, a left forelimb and two hindlimbs.