-
earliest mandeloceratid is
Pseudogomphoceras which gave rise to
Ovocerina.
Ovocerina gave rise to Cinctoceras, Umbeloceras, Vesperoceras, and Mandaloceras...
- †Orthoceras †Orthocycloceras †Orthonybyoceras †Osbornoceras †Ovoceras †
Ovocerina †Oxfordoceras †Oxygonioceras †Oxynautilus †Pachendoceras †Pachtoceras...