In anatomy, the atlas (C1) is the most superior (first) cervical vertebra of the spine and is located in the neck.
Atlas from above
Atlas from above
Atlas, inferior surface
In tetrapods, cervical vertebrae are the vertebrae of the neck, immediately below the skull. Truncal vertebrae lie caudal of cervical vertebrae. In sauropsid species, the cervical vertebrae bear cervical ribs. In lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.
Scrollable computed tomography images of normal cervical vertebrae
X-ray of cervical vertebrae
X-ray of cervical spine in flexion and extension
Image: X ray of vertebral lines