Cyclostomiceratidae

Systematics
 * Class Cephalopoda
 * Subclass Nautiloidea
 * Order Ellesmerocerida
 * Family Cyclostomiceratidae

The Cyclostomiceratidae, named by Foerste, is a family within the Ellesmerocerida, derived from the Baltoceratidae. Its shells, Cassinian in age, are generally straight, breviconic (i.e. short) and well expanded. Apertures are contracted, the body chamber narrowing at the front end, but not contracted. Siphuncles lie close to the lower, ventral margin. Septal necks are short and tend to be divergent. Connecting rings, thick and layered.

Genera include Cyclostomiceras, from eastern North America, and Paracylostomiceras from Argentina

References
 * Rousseau H. Flower 1964, The Nautiloid Order Ellesmerocerida (Cephalopoda). New Mexico Bureau of Mines and Mineral Resources Memoir 12.