Lateral view (venter to the right) and cross-section of Oncoceras constrictum. Figure from Sweet (1964).

Belongs within: Oncoceratidae.

Oncoceras was a genus of oncocerid cephalopods found from the Middle to Upper Ordovician.

Characters (from Sweet 1964): Compressed, curved brevicones, gibbous behind body chamber and contracting to aperture. At gibbous region, convexity of ventral profile typically increased; dorsal profile concave adapically, convex over gibbous region. Siphuncle small, ventral; segments ovoid to scalariform, generally longer than wide.

<==Oncoceras Hall 1847 [=Onoceras (l. c.)] S64
    |--*O. constrictum Hall 1847 S64
    |--O. arcticum Schuchert 1900 P68
    |--O. covingtonense Flower 1946 P68
    |--O. exile Flower 1946 P68
    |--O. fossatum Flower 1946 P68
    |--O. parvum Foerste 1935 P68
    |--O. pupaeforme Ruedemann 1921 P68
    |    |--O. p. pupaeforme P68
    |    `--O. p. femina Ruedemann 1926 P68
    `--O. tumidum Schuchert 1900 P68

*Type species of generic name indicated


[P68] Purnell, L. R. 1968. Catalog of the Type Specimens of Invertebrate Fossils. Part I: Paleozoic Cephalopoda. United States National Museum Bulletin 262: 1-198.

[S64] Sweet, W. C. 1964c. Nautiloidea – Oncocerida. In Treatise on Invertebrate Paleontology pt. K. Mollusca 3. Cephalopoda – General Features – Endoceratoidea – Actinoceratoidea – Nautiloidea – Bactritoidea (R. C. Moore, ed.) pp. K277-K319. The Geological Society of America and the University of Kansas Press.

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