Description

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

54mm nautiloid.

Cephalopod.

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.

Nautiloids later declined in diversity during the Devonian but continued to be significant elements of marine faunas over the rest of the Paleozoic Era.  They endured the worst mass extinction in the history of the earth and rediversified during the Mesozoic, surviving into the Cenozoic and finding success again before going into decline by the end of the Miocene.

Today, only a few species survive in areas of the Indo-Pacific.