Xenoposeidon is based on BMNH R2095, a partial posterior back vertebra. The specimen lacks the anterior face of the centrum and the upper portion of the neural arch. The centrum is estimated at 200 millimetres (7.9 in) long, and the height of the preserved portion of the vertebra is 300 millimetres (11.8 in). The average diameter of the posterior face of the centrum is 165 millimetres (6.50 in), with a concave surface. This concavity is deep enough to suggest that the anterior faces of vertebrae from this part of the dinosaur's spine would have been convex to articulate with such a shape.[2]