Our first record of Camarasaurus ("Chambered lizard") comes from 1877, when a few scattered vertebrae where located in Colorado by O.W. Lucas. Legendary paleontologist Edward Drinker Cope payed for the bones as part of his long-running and acrimonious competition with Othniel Charles Marsh, and named them in the same year.
It was not until 1925 that a complete skeleton of Camarasaurus was recovered, by Charles W. Gilmore. However, that was the skeleton from a young Camarasaurus and so many illustrations of the dinosaur from the time show it to be much smaller than we now know it to be.
The Morrison Formation along the eastern flank of the Rocky Mountains is home to a rich stretch of late Jurassic rock. A large number of dinosaur species can be found here, including Camarasaurus' relatives such as Diplodocus, Apatasaurus and Brachiosaurus. However, Camarasaurus was surely the most abundant of all the dinosaurs recovered from the Formation, and we now have a number of complete skeletons from Colorado, New Mexico, Utah, and Wyoming.
Camarasaurus was a quadripedal herbivorous sauropod of average size - approximately 18 metres in length, and weighing around 28 tonnes. It lived in the late Jurassic period, between 155 and 145 million years ago. The main feature of interest of this dinosaur is its skull. The skull was remarkably square with a blunt snout and, while sturdy and frequently recovered in good condition, had many holes. The huge nostrils, positiond in front of the eyes, probably held a large area of moist membrane to cool the brain in the hot weather of Jurassic North America.
The 19cm-long teeth were shaped like chisels and arranged evenly along the jaw - most diplodocids had their teeth concentrated at the front. The strength of the teeth indicates that Camarasaurus probably ate corser plant material than most other diplodocids. Like a chicken, it would probably have swallowed stones to help physically digest the food in the stomach, and then regurgitated them when they became too smooth. Consistent with this suggestion, the Morrison Formation seems to include a large number of isolated piles of unusually smoothed stones.
Each giant foot bore five toes, with the inner toe having a large sharpened claw for self-defence. Like most sauropods, the front legs were shorter than the hinds, but the high position of the shoulders meant there was little slope in the back. In some sauropods, there were long upward projections on each vertebra, but the absence of such structures from the spine of Camarasaurus suggests that it was not able to raise itself up on its hind legs. The vertebrae were nevertheless specialised though; as a weight-saving device seen in many later sauropods, the vertebrae were hollowed out, hence the name "Chambered lizard". Like a modern elephant, Camarasaurus appears to have had a "wedge" of spongy tissue at the base of the heel, to take the weight of such a large creature. The neck, and counter-balancing tail, were shorter than usual for a sauropod of this size.
We have a fossil record of adults and young that died together. This suggests that Camarasaurus travelled in herds. Also, recovered Camarasaur eggs are found in lines, not in neatly arranged nests as with other dinosaurs. Like most sauropods, it seems Camarasaurus did not care for its young. It is suggested by some paleontologists that each Camarasaurus may have lived for up to a hundred years!
Camarasaurus, again like certain other sauropods, had an enlargement of the spinal cord near the hips. Paleontologists originally believed this to be a second brain - perhaps necessary to co-ordinate such a huge creature! However, modern opinion asserts that, while it was an area of large nervous activity, it was nevertheless unconcious. However, this enlargement was actually larger than the remarkably small brain contained in the animals' box-like skull.
Cope's original Camarasaurus was species C. supremus
("The biggest chambered lizard"). Other species since discovered include C. grandis
, C. lentus
, and C. lewisi