Ophidioceratidae

Ophidioceratidae Temporal range: U Silurian
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Tarphycerida
Family:	Ophidioceratidae Hyaatt, 1894

The Ophidioceratidae is a family of closely coiled tarphycerids, represented solely by the Upper Silurian genus, Ophioceras, characterized by an evolute shell with narrow, subrounded, annulated whorls and a subcentral siphuncle composed of thin connecting rings that show no evidence of layering. The mature body chamber is strongly divergent and is the longest proportionally of any tarphycerid. The aperture has a deep hyponomic sinus and occular sinuses, and so resembles some lituitids.

The Ophidioceratidae seems to have its origin in the Trocholitidae, possibly in Graftonoceras.

References

• Furnish, W. M, and Glenister, Brian F. 1964. Nautiloidea - Tarphycerida, Treatise on Invertebrate Paleontology, Part K, Geo Soc. of America. Teichert and Moore (eds.)