Cephalopoda - Ammonoidea - Nostoceratidae
Alternative spelling: Nostoceras (Didymoceras)
Synonyms: Didymoceratoides Kennedy and Cobban 1993, Emperoceras Hyatt 1894
Parent taxon: Nostoceratidae according to W. J. Kennedy et al. 2000
Sister taxa: Anaklinoceras, Ankinatsytes, Axonoceras, Bostrychoceras, Cirroceras, Eubostrychoceras, Exiteloceras, Helicoceras, Jouaniceras, Nostoceras
Subtaxa: Didymoceras angulatum, Didymoceras binodosum, Didymoceras californicum, Didymoceras cheyenense, Didymoceras cheyennense, Didymoceras cochleatus, Didymoceras hornbyense, Didymoceras navarroensis, Didymoceras nebrascense, Didymoceras newtoni, Didymoceras nicolletii, Didymoceras platycostatum, Didymoceras stevensoni, Didymoceras subtuberculatum, Didymoceras tenuicostatus, Didymoceras tortus, Didymoceras tricostatus, Didymoceras umbilicatus, Didymoceras uncus, Didymoceras vespertinus
Ecology: fast-moving nektonic carnivore