Camptosaurus ( ) is an extinct genus of plant-eating, beaked ornithischian dinosaurs of the Late Jurassic period of western North America and possibly also Europe. The name means 'flexible lizard' (Greek (') meaning 'bent' and (') meaning 'lizard').
History of discovery
thumb|left|Historical skeletal restoration by O.C. Marsh, with skull based on remains now referred to Theiophytalia
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. The genus was renamed Camptosaurus by him in 1885 because the original name was already in use for a cricket. 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. 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. Charles W. Gilmore named two additional species, C. browni and C. depressus in his 1909 redescription of the Marsh specimens. In the Morrison Formation, Camptosaurus fossils are present in stratigraphic zones 2–6.
thumb|Outdated mount of a C. nanus skeleton at the AMNH, now thought to be a growth stage of C. dispar
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.
thumb|left|Camptosaurus skeleton mounted in outdated quadrupedal posture, and with [[Theiophytalia skull, Natural History Museum of Milan]]
Camptosaurus depressus was recovered from the Lakota Formation near the town of Hot Springs, South Dakota. It was described by Charles Gilmore in 1909 based on the holotype and only known specimen USNM 4753, a fragmentary postcranium, by the "narrowness or depressed nature of the ilia". However, McDonald and colleagues (2010), and McDonald (2011) found that the horizontal postacetabular process of C. depressus is more likely a product of distortion. Therefore, McDonald put it into its own genus, Osmakasaurus. An additional species, Camptosaurus aphanoecetes, was named by Carpenter and Wilson in 2008 for specimens from Dinosaur National Monument. C. valdensis consists of the holotype and only known specimen NHMUK R167, a poorly preserved left femur lacking the distal end. It was earlier believed to be a dubious dryosaurid, C. leedsi is probably a valid dryosaurid that has been moved to the new genus Callovosaurus. C. hoggii was originally named Iguanodon hoggii by Richard Owen in 1874 and was moved to Camptosaurus by Norman and Barrett in 2002. It has since been transferred to the genus Owenodon.
The remaining European species Camptosaurus prestwichii was recovered from Chawley Brick Pits, Cumnor Hurst in Oxfordshire in England. The fossil was found when a tramway was driven into the side of a hill. It was described by Hulke in 1880 as Iguanodon prestwichii, and then placed in its own genus Cumnoria by Seeley in 1888, but was soon sunk into Camptosaurus by Lydekker in 1889. However, Naish & Martill (2008), McDonald and colleagues (2010), and McDonald (2011) found that Seeley's original generic distinction was valid. Cumnoria has been recovered as a styracosternan, more closely related to advanced iguanodonts than to Camptosaurus dispar, similar to the case of Uteodon. hence its tentative placement within the Camptosaurus genus. The Quarry 13 individuals are smaller though. It is estimated that Camptosaurus typically reached long and weighed .
thumb|Restoration of six [[ornithopod dinosaurs, including Camptosaurus at the far left]]
Paleobiology
thumb|Camptosaurus dispar (blue) compared in size to a human and other ornithopods
Based on studies of other iguanodonts (clade Iguanodontia), scientists believe they may have been able to achieve running speeds of 25 km per hour (15 mph).