Procymatoceras

Procymatoceras is a nautiloid cephalopod from the Middle Jurassic with a large, tightly involute, rapidly expanding shell. Early, inner, whorls are round in cross section. Later, outer, whorls, and mature living chamber are flattened on the sides and venter. Surface covered with sinuous ribs. Sutures have shallow ventral and dorsal lobes. Probably gave rise to Cymatonautilus and is the likely ancestor of Cymatoceras and Paracymatoceras. Procymatoceras has its origin in the earliest Nautilidae, in Cenoceras.

Procymatoceras Temporal range: Middle Jurassic
Fossil of Procymatoceras subtruncatus
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Nautilida
Family:	†Cymatoceratidae
Genus:	†Procymatoceras Spath, 1927

References

• Bernhard Kümmel, 1964. Nautiloidea - Nautilida. Treatise on iInvertebrate Paleontology Part K. Geol. Soc. of America and Univ. Kans. Press, Teichert & Moore (eds)