Ulrichoceras

Ulrichoceras Temporal range: M Ordovician
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Discosorida
Family:	Cyrtogomphoceratidae
Genus:	Ulrichoceras Foerste, 1925

Ulrichoceras is recognised as the basal cyrtogomphoceratid genus, which is the source for the rest of the Cyrtogomphoceratidae as well as for the Westonoceratidae. The Cyrtogomphoceratidae are endogastric, the Westonoceratidae, exogastric.

Ulrichoceras has a cyrtoconic, endogastric shell that expands fairly rapidly to the middle of the body chamber, then contracts toward the aperture. The cross section is slightly depressed, atypical for cyrtogomphoceratids but not so for Reudemannoceratids; dorsal and ventro lateral sides are broadly rounded, the venter moderately flattened. Sutures have broad ventral lobes. The siphuncle is between the center and the venter; segments are short and not strongly contracted at the septal foremina, connecting rings are thickened and have enlarged bullettes.

Ulrichoceras, named by Foerste, 1925, type U. beloitense, comes from the Middle Ordovician of Wisconsin, U.S.A. It is intermediary in form between Reudemanoceras and the more derived, M -U Ordovician, Strandoceras.

See also

• Nautiloid
  • List of nautiloids

References

• Flower, R H and Teichert, C; 1957. The Cephalopod Order Discosorida. University of Kansas Paleontological Contributions. Mollusca, Article 6, pp 1–144.
• Teicher, C. 1964. Nautiloidea-Discosorida. Treatise on Invertebrate Paleontology, Part K. Teichert and Moore, eds.