Camarasaurus (/ˌkæmərəˈsɔrəs/ kam-ə-rə-sawr-əs) was a genus of quadrupedal, herbivorous dinosaurs. It was the most common of the giant sauropods to be found in North America. Its fossil remains have been found in the Morrison Formation of Colorado and Utah, dating to the late Jurassic Period (late Oxfordian to Tithonian stages), between 155 and 145 million years ago.
The name means “chambered lizard”, referring to the hollow chambers in its vertebrae (Greek καμαρα/kamara meaning “vaulted chamber”, or anything with an arched cover, and σαυρος/sauros meaning “lizard”).
Camarasaurus is among the most common and frequently well-preserved sauropod dinosaurs. The maximum size of the most common species, C. lentus, was about 15 meters (50 ft) in length. The largest species, C. supremus, reached a maximum length of 23 meters (75 ft) and maximum estimated weight of 47 tonnes (51.8 tons).
The arched skull of Camarasaurus was remarkably square and the blunt snout had many fenestrae, though it was sturdy and is frequently recovered in good condition by paleontologists. The 19 centimeter long (7.5 in) teeth were shaped like chisels (spatulate) and arranged evenly along the jaw. The strength of the teeth indicates that Camarasaurus probably ate coarser plant material than the slender-toothed diplodocids.
Each front limb bore five toes, with the inner toe having a large sharpened claw. Like most sauropods, the front limbs were shorter than the hind legs, but the high position of the shoulders meant there was little slope in the back.
Serving the purpose of weight-saving, as seen in other sauropods, many of the vertebrae were hollowed out or pneumatic, riddled with passages and cavities for an intricate system of air sacs connected to the lungs. This feature was relatively unknown at the time Camarasaurus was discovered, and was the inspiration for its name, meaning “chambered lizard”. The neck and counterbalancing tail were shorter than usual for a sauropod of this size. Camarasaurus, again like certain other sauropods, had an enlargement of the spinal cord near the hips. Palaeontologists originally believed this to be a second brain, perhaps necessary to co-ordinate such a huge creature. However, while it would have been an area of large nervous, probably reflex (automatic) activity, it was not a brain, and such enlargements are actually found to some degree in all vertebrate animals.
The first record of Camarasaurus comes from 1877, when a few scattered vertebrae were located in Colorado, by Oramel W. Lucas. The paleontologist Edward Drinker Cope paid for the bones, as part of his long-running and acrimonious competition with Othniel Charles Marsh (known as the Bone Wars) and named them in the same year. Marsh later named some of his sauropod findings Morosaurus grandis but most paleontologists today consider this to be a species of Camarasaurus. Such naming conflicts were common between the two rival dinosaur hunters, the most famous being Brontosaurus and Apatosaurus.
It was not until 1925 that a complete skeleton of Camarasaurus was recovered, by Charles W. Gilmore. However, it was the skeleton from a young Camarasaurus, which is why so many illustrations of the dinosaur from the time show it to be much smaller than it is now known to be.