their sockets as the gums retracted, dried, and tightened through decay. The examinations of the specimen also indicate that the teeth were covered by tough outer scales and possibly a beak of some variety, though this is not known for certain. The neck of Camarasaurus was of only moderate length by sauropod standards. It was composed of 12 vertebrae. Most of the cervical neural spines were bifurcated, with more vertebrae developing bifurcated neural spines as the animal grew. As in other sauropods, the vertebrae of the neck and torso contained chambers that in life were filled by air sacs connected to the respiratory system. The air sacs could take up more than half of the space inside the vertebrae, making them as highly pneumatic as the bones of birds. It is these chambers that give Camarasaurus its name, "chambered lizard". The tail of Camarasaurus was composed of 53 vertebrae. Classification and species Camarasaurus is the type genus of the family Camarasauridae, members of which are medium-sized Macronarian sauropods that mostly date to the Late Jurassic. Camarasaurids had shorter forelimbs than hindlimbs, large scapulacoracoids, and longer tails than necks. When Edward Cope described Camarasaurus in 1877, he believed it was a dinosaur closely related to Cetiosaurus, Bothriospondylus, Ornithopsis, Anchisaurus (Megadactylus), and Pneumatosteus, but didn’t name a group for these taxa until the description of Amphicoelias when he erected Camarasauridae. Camarasaurus is the only taxon uncontroversially regarded as a valid genus of camarasaurid. It contains four species: C. grandis, C. lentus, C. lewisi, and C. supremus. C. lewisi may represent a distinct genus, Cathetosaurus. Lourinhasaurus, the type species of which was formerly assigned to Camarasaurus, is regarded as a camarasaurid by most studies, though it has also been considered to be a basal eusauropod. A simplified cladogram of basal Macronaria after Tan et al (2020) is shown below: Camarasaurus is considered to be a basal macronarian, more closely related to the common ancestor of all macronarians than to more derived forms like Brachiosaurus. Species Camarasaurus is regarded as containing four valid species by most researchers: C. grandis, C. lentus, C. lewisi, and C. supremus. C. supremus, the species named by Cope in 1877, is the type species. C. grandis was named in 1877 and C. lentus in 1889. The fourth species, C. lewisi, is of uncertain affinities. It was originally described as a distinct genus, Cathetosaurus, in 1988, but reclassified as a