Acutimitoceras
Acutimitoceras is a genus belonging to the Acutimitoceratinae subfamily of the Prionoceratidae family, a member of the Goniatitida order. They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopuses, and cuttlefish, and more distantly to the nautiloids. References

 The Paleobiology Database accessed on 10/01/07

Goniatitida genera
Prionoceratidae
Ammonites of North America
Ammonites of Europe