The Upper Jurassic genus Camarasaurus ( Cope,1877,1878 Osborn and Mook,1921 Gilmore,1925) is the most common North American sauropod and the only one for which all parts of the skeleton are known. The powerfully built skull is short and high, with a "buldog" shaped muzzle. Huge weight-saving hollows in its vertebrae gave this sauropod its name, "chambered lizard". 

Camarasaurus was more massive than the more famous Diplodocus but had a shorter neck and tail, relatively long forelimbs and high shoulders, and stood with its back almost horizontal rather than rising to the hips. Wereas Diplodocus had a small, low, horse- like head, Camarasaurus's head was large and deep, with a muzzlemore like a bulldog's. 

Big eye sockets, nostrils, and other cavities reduced some skull bones to lightweight struts.  Big skull cavities for the eyes and nostrils suggest that this sauropod had keen senses of sight and smell that would have helped it find new feeding grounds and detect where dangerous theropods lurked. Camarasaurus probably moved around in mixed-age herds. 

There is no proof for this, but whitout adults to protect it, a young Camarasaurus would have been vulnerable to any hungry Allosaurus or Ceratosaurus. Even the great size, tough hide, and sharp thumb-claws of a solitary adult might not have saved it from a hunting pack of big, flesh-eating dinosaurs. 

Camarasaurus bones have been discovered deeply scored with the characteristic teeth-marks of Allosaurus and Ceratosaurus. It is possible, however, that these predators were beasts they had not killed but found dead. Camarasaurus relatively short, high snout, short neck, high shoulders, compact body, and short tail seem closer to giraffe-like Brachiosaurus than to the long- necked, long-tailed Diplodocus. 

Caudal vertebrae (tail bones) featured forked bones. These chevrons guarded a blood vessel that ran under the centra (vertebral"cores" ). Each chevron's long lower spine provided a site of attachement for muscles. Length 18 m (59 ft) Weight 20 tonnes.