Didymoceras

Didymoceras Temporal range:
Artist's reconstruction of D. stevensoni, D. nebrascensis, and D. cheyennese
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Suborder:	†Ancyloceratina
Superfamily:	†Turrilitaceae
Family:	†Nostoceratidae?
Genus:	†Didymoceras Hyatt, 1894
Species
See text
Synonyms
Cirroceras Conrad, 1866 Helicoceras d'Orbigny, 1842 Helicoceras Whitfield, 1877 Emperoceras Hyatt, 1894 Didymoceratoides Kennedy & Cobban, 1993

Didymoceras is an extinct genus of ammonite cephalopod. It is one of the most bizarrely shaped genera, with a shell that spirals upwards into a loose, hooked tip. It is thought to have drifted in the water vertically, moving up and down. The generic name is Latin for "paired horns".

Its taxonomic place is often in flux, being placed in either Turrilitidae, Nostoceratidae, or its own family, Didymoceratidae. Species included in the genus are the following:

• Didymoceras angulatum (Meek and Hayden 1860)
• Didymoceras binodosum (Kennedy and Cobban 1993)
• Didymoceras californicum Anderson 1958
• Didymoceras cheyenense (Meek and Hayden 1856)
• Didymoceras cheyennense (Meek and Hayden 1856)
• Didymoceras cochleatus (Meek and Hayden 1858)
• Didymoceras hornbyense (Whiteaves 1876)
• Didymoceras navarroensis (Shumard 1861)
• Didymoceras nebrascense (Meek and Hayden 1856)
• Didymoceras newtoni (Whitfield 1877)
• Didymoceras nicolletii (Hall and Meek 1856)
• Didymoceras platycostatum (Kennedy and Cobban 1993)
• Didymoceras stevensoni (Whitfield 1877)
• Didymoceras subtuberculatum Howarth 1965
• Didymoceras tenuicostatus (Meek and Hayden 1858)
• Didymoceras tortus (Meek and Hayden 1858)
• Didymoceras tricostatus (Whitfield 1897)
• Didymoceras umbilicatus (Meek and Hayden 1858)
• Didymoceras uncus (Meek and Hayden 1858)
• Didymoceras vespertinus (Conrad 1874)