Platyceras is a genus of extinct Paleozoic gastropods in the family Platyceratidae

Platyceratidae

Platyceratidae is an extinct family of Paleozoic gastropods of uncertain position in the clade Neritimorpha...

 known from the Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 to the Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

 periods. It is the type genus of the family Platyceratidae.

Description

Platyceras has distinctive shape that is easily recognized. The cap-like shell is high and broad anteriorly. The posterior portion of the shell, at the apex, is usually slightly coiled in an asymmetrical fashion. Frequently, the front portions of the shells are broken, though the posterior sections are relatively well preserved. Platyceras is particularly abundant in Devonian deposits (359 million to 416 million years old.) Platyceras and other platyceratid gastropods

Platyceratidae

Platyceratidae is an extinct family of Paleozoic gastropods of uncertain position in the clade Neritimorpha...

 are known for the complex symbiotic relationships they had with crinoids.