Camptosaurus (/ˌkæmptəˈsɔːrəs/ KAMP-tə-SOR-əs) is a genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America and possibly also Europe.[1] The name means 'flexible lizard' (Greek καμπτος (kamptos) meaning 'bent' and σαυρος (sauros) meaning 'lizard').
Camptosaurus is a relatively heavily built form, with robust hindlimbs and broad feet, still having four toes.[2] Due to the separate status of Uteodon it has become problematic which material from the Morrison Formation belongs to Camptosaurus. The specimens with certainty belonging to Camptosaurus dispar, from Quarry 13, have been recovered from very deep layers, probably dating to the Callovian-Oxfordian.[3] The largest fragments from later strata indicate adult individuals more than 7.9 metres (26 ft) long, and 2 metres (6.6 ft) at the hips.[4] The Quarry 13 individuals are smaller though. They have been described as reaching 6 meters (19.7 feet) in length and 785 – 874 kg in weight.[5] In 2010 Gregory S. Paul gave an even lower estimate: a length of five metres and a weight of half a tonne.[6]
Earlier reconstructions, such as those by Marsh and Gilmore, were based on the skull of Theiophytalia and display an incorrect, more rectangular profile. The skull was in fact triangular with a pointed snout, equipped with a beak. Its teeth were more tightly packed in the jaw compared to other Morrison euornithopods.[5] Museum curator John Foster describes them as having "thick median ridges on their lateral sides and denticles along their edges," these features were similar to, but "more fully developed" than those in Dryosaurus.[5] Camptosaurus teeth frequently exhibit extensive wear, which indicates that individuals in the genus had a diet of relatively tough vegetation.[5]
On September 4, 1879 William Harlow Reed in Albany County, Wyoming found the remains of a small euornithopod. That same year Professor Othniel Charles Marsh described and named the find as Camptonotus, or "flexible back", from Greek κάμπτω, "to bend" and νῶτον, "back", in reference to the presumed flexibility of the sacral vertebrae. The holotype was YPM 1877, a partial skeleton.[7] The genus was renamed Camptosaurus by him in 1885 because the original name was already in use for a cricket.[8] In 1879, Marsh named C. dispar (type species of the genus) for material he received from his collectors at Quarry 13 near Como Bluff, Wyoming in the Morrison Formation and C. amplus based on the holotype YPM 1879, a foot found by Arthur Lakes at Quarry 1A. The foot was later shown to have belonged to Allosaurus.[2][9] Throughout the 1880 and 1890s, he continued to receive specimens from Quarry 13 and in 1894 named two additional species: C. medius and C. nanus, based in part on size.[10] Charles W. Gilmore named two additional species, C. browni and C. depressus in his 1909[11] redescription of the Marsh specimens. In the Morrison Formation, Camptosaurus fossils are present in stratigraphic zones 2–6.[12]
Then in 1980, Peter Galton and H.P. Powell in their redescription of C. prestwichi (see following), considered C. nanus, C. medius and C. browni to be different growth stages or different gender of the larger C. dispar, and therefore only C. dispar was a valid species.[2] They also considered a skull, YPM 1887, in 1886 referred to C. amplus by Marsh, later confirmed by Gilmore, to belong to C. dispar as well. Gilmore had used this skull to describe the skull of Camptosaurus, but the specimen was recently shown by Brill and Carpenter not to belong to Camptosaurus. In 2007, they put it into its own genus and species, Theiophytalia kerri.[13]