bony vertebral centrum amphicoelous The tuatara spine is made up of hourglass-shaped amphicoelous vertebrae, concave both before and behind. This is the usual condition of fish vertebrae and some amphibians, but is unique to tuatara within the amniotes[Wikipedia]. This class was sourced from an external ontology (amphibian_anatomy). Its definitions, naming conventions and relationships may need to be checked for compatibility with uberon UBERON:3000717 Ectochordal, biconcave or terminally flat vertebral centrum. This design seems to allow limited motion in most directions. An intervertebral body (which may or may not be independent from the adjacent centra) fills the cavity between successive centra. The intervertebral body usually is formed by soft material that may be derived, at least in part, from the embryonic notochord.