Camarasaurus (ˌkæmərəˈsɔːrəs ) was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch (Kimmeridgian to Tithonian stages), between 155 and 145 million years ago.
Camarasaurus presented a distinctive cranial profile of a blunt snout and an arched skull that was remarkably square, typical of basal Macronarians.
The name means "chambered lizard", referring to the hollow chambers, known as pleurocoels, in its cervical vertebrae (Greek καμαρα (kamara) meaning "vaulted chamber", or anything with an arched cover, and σαυρος (sauros) meaning "lizard".
Camarasaurus contains four species that are commonly recognized as valid: Camarasaurus grandis, Camarasaurus lentus, Camarasaurus lewisi, and Camarasaurus supremus. C. supremus, the type species, is the largest and geologically youngest of the four. Camarasaurus is the type genus of Camarasauridae, which also includes its European close relative Lourinhasaurus.
Camarasaurus was named in 1877 by Edward Drinker Cope, during the period of scientific rivalry between him and Othniel Charles Marsh known as the Bone Wars. Soon after, Marsh named a genus Morosaurus, but it was subsequently shown to be synonymous with Camarasaurus.
The first record of Camarasaurus comes from the spring of 1877 when Mr. Oramel William Lucas of Cañon City, Colorado discovered some large vertebrae at Garden Park, which he sent to Edward Drinker Cope who was based in Philadelphia, Pennsylvania. The original material sent consisted of a partial cervical vertebra, which would become the taxon's namesake, three dorsal vertebrae, and four caudal vertebrae. This specimen is now thought to have been composed of several individuals. From these initial fragmentary remains, Cope made his original description of Camarasaurus supremus (“supreme chambered lizard”) and founded the genus; these remains are now in the American Museum of Natural History under the catalogue number AMNH 560.