Systematic Paleontology
Class:Cephalopoda
Subclasss: Nautiloidea
Order: Nautilida
Family: Solenochilidae
Genus: Acanthonautilus
Acanthonautilus is a solenochilid genus found in the upper Mississippian Visean of Europe and North America. The shell of Acanthonautilus is smooth and evolute, the outer rim is broadly rounded in cross section. The final whorl encloses the previous, or earlier. Fully grown, mature shells have lateral umbilical projections on either side. Chambers are long, sutures fairly straight. The siphuncle is ventral, running along the inside of the outer rim. Septal necks are short, connecting rings thin. Siphuncle segments are only slightly expanded, unlike those in the related Solenochilus.
References
Bernhard Kummel 1964. Treatise on Invertebrate Paleontology Part K, K441
On a New Genus and Species of Nautilus-like shell (Acanthonautilus bispinosus) from the Carboniferous limestone of Ireland. [1]