Silurian characterized by short, essentially straight shells referred to as breviconic, typically with a faintly exogastric shape produced by the profile of the body chamber.

The narrow hyponomic sinus, which is an opening for the water-jet funnel by which the animal could move, much as with modern squid and octopods, points toward the lower or ventral side.

Mandaloceras is the type genus of the Mandaloceratidae characterized by straight or somewhat curved shells with a slightly depressed cross section (width greater than height) and a constricted T-shaped aperture.

Cinctoceras is a large mandaloceratid with a breviconic shell that tends to be dorsally flattened, making its cross section slightly depressed; a constricted T-shape aperture and siphuncle segments that are short and broad.

Vesperoceras is a medium size, generally straight, breviconic mandaloceratid with a broad annular expansion to the anterior part of the phragmocone followed by a constriction at the base of the body chamber.