Chordates: Animals that at some stage in their life cycle have a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail.
Spinal column: The part of the axial skeleton that encases and protects the spinal cord, composed of vertebrae that replace the embryonic notochord in most adult vertebrates.
Central nervous system: Comprises the brain and spinal cord, controlling most functions of the body and mind; it develops around the axis established by the notochord during embryogenesis