Gonatocyrtoceras

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

Gonatocyrtoceras is a genus of oncocerid nautiloids belonging to the family Acleistoceratidae, that lived during the Middle Devonian. Gonatocyrtoceras is characterized by strongly curved, depressed, breviconic shells. Curvature is exogastric, meaning the lower, or ventral, side is convex in longitudinal profile. The aperture is without a hyponomic sinus. The siphuncle is small and subventral.

Other Devonian Acleistoceratidae are Acleistoceras, Paracleistoceras, and Poteriocerina.

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.