Temporal range: Eocene
Belosaepia reached 18 centimetres (7.1 in) in length and 5 centimetres (2.0 in) across; it had a large siphuncle that penetrated its oblique septa. The shell was endogastrically coiled. It had a small belemnite-like guard, which took the form of a short horn at the posterior end of the shell; usually, only a small portion of the shell closest to the guard is preserved. The chambers in the shell closely resemble those present in the cuttlebone of modern cuttlefish.
Belosaepia lived close to the sea floor.
- Yancey, T. E.; Garvie, C. L.; Wicksten, M. (2010). "The Middle Eocene Belosaepia ungula (Cephalopoda: Coleoida) from Texas: Structure, Ontogeny and Function" (PDF). Journal of Paleontology. 84 (2): 267–287. doi:10.1666/09-018R.1.
- e.g. "Functional Morphology of the Eocene Coleoid Belosepia".