Phenacoceratidae is one of three families of the Dimeroceratoidea superorder, a member of the Goniatitida order. They are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopodes, and cuttlefish, and more distantly to the nautiloids. References The Paleobiology Database accessed on 10/01/07 Goniatitida families Dimeroceratoidea