Grimsbyoceras

Grimsbyoceras Temporal range: Mid Devonian
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Oncocerida
Family:	Acleistoceratidae
Genus:	Grimsbyoceras Foerste, 1926

Grimsbyoceras is a nautiloid genus included in the Oncocerida order of the family Acleistoceratidae that lived during the Middle Devonian. They have been found in North America (Illinois) and central Europe.

Grimsbyoceras, named by Foerste in 1926, has a depressed, breviconic shell, with an elliptical transverse aperture, without a hyponomic sinus, and a small, subventral siphuncle. The phragmocone is rapidly expanding and strongly exogastric. The body chamber is attached at knee-like bends on the ventral and lateral sides.

Acleistoceras and Poteriocerina are similar acleistoceratids from the Middle Devonian, differing primarily in internal detail.

References

• R.C. Moore, ed. (1964). Part K, Mollusca 3. Treatise on Invertebrate Paleontology. Lawrence, Kansas: Geological Society of America and University of Kansas Press. p. K190–K216.