What is "dimorphocerataceae"

The Dimorphocerataceae, Dimorphoceratoidea in more recent classifications, is one of seventeen superfamilies included in the ammonoid suborder Goniatitina, a variety of shelled cephalopods that lived during the late Paleozoic.

The Dimorphocerataceae can be described as Goniatitina with subdiscoidal to lenticular shells that have conspicuous closed umbilici and goniatitic sutures with long prominently bifid ventral lobes and more or less subdivided external lobes.