†family Sphenodiscidae Hyatt 1900 (ammonite)
Parent taxon: Acanthocerataceae according to W. J. Kennedy et al. 1997
Sister taxa: Acanthoceratidae, Brancoceratidae, Coilopoceratidae, Collignoniceratidae, Flickiidae, Forbesiceratidae, Leymeriellidae, Libycoceratidae, Lyelliceratidae, Prolyelliceratidae, Pseudotissotiidae, Vascoceratidae
Subtaxa: Eulophoceras, Manambolites, Sphenodiscus
Ecology: fast-moving nektonic carnivore