Tarphyceratidae

Tarphyceratidae comprises a family of closely coiled tarphycerids with a dorsal impression in the whorls and a ventral siphuncle that lived during the Early Ordovician. Shells are smooth or ribbed, body chamber about half a whorl in length, hyponomic sinus deep and rounded. Siphuncles are are ventral, with straight septal necks and thick layered connecting rings in the Ellesmerocerids. As with other tarphycerids, shells tend to diverge at maturity. Derivation is from the loosely coiled Estoniocertidae.

The Barrandeocerida has its origin in the Tarphyceratidae as does the Trocholitidae and possibly the Lituitidae.

Genera assigned to the Tarphyceratidae include:

Tarphyceras

Cambelloceras

Centrotarphyceras

Cycloplectoceras

Eurystomites

Moreauoceras

Pilotoceras

Pionoceras

Seelyoceras