Turnoceras

Turnoceras Temporal range: Devonian
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	†Oncocerida
Family:	†Nothoceratidae
Genus:	†Turnoceras Foeste, 1926

Turnoceras is a genus of Devonian cephalopods belonging to the oncocerid family Nothoceratidae. Its shell is broadly expanding and exogastrically curved such that the flattened dorsum is on longitudinally concave side. Aperture unconstricted with no hyponomic sinus for the water jet funnel. siphuncle along the outer, ventral, side, with radial, plate-like actinosiphonate deposits occupying the interior.

Conostichoceras is similar externally, but has a siphuncle with a trapezoidal aspect to its siphuncle segments. Perimecoceras has similar concave siphuncle segments but is tubular in form.

References

• Sweet, W.C. 1964; Nautiloidea -Oncocerida; Treatise on Invertebrate Paleontology, Part K ; Geological Society of America and University of Kansas press; Teichert and Moore (eds).
• Turnoceras-Paleodb
• Sepkoski Cephalopod Genera