Dimorphoceratoidea is one of seventeen superfamilies included in the ammonoid suborder Goniatitina, a variety of shelled cephalopods that lived during the late Paleozoic. The Dimorphoceratoidea 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. References Miller, A.K. et al. Paleozoic Ammonoidea. Treatise on Invertebrate Paleontology. Geological Society of America and University Kansas Press. Dimorphoceratoidea in GONIAT Online 5/30/12 The Paleobiology Database 10/01/07 Goniatitida superfamilies Goniatitina