Description

Oneotoceras percurvatum
Nautiloid
Lower Ordovician
Gasconade Dolomite
Ozarks, Sullivan, Missouri, USA

Big 71mm nautiloid.

Oneotoceras is an extinct genus of nautiloid from the Ordovician of North America (sites in the U.S.A.).  It lived at a time when nautiloids were becoming the apex predators of the seas.