Didymoceras
Didymoceras is an extinct genus of ammonite cephalopod from the Late Cretaceous epoch. 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 genus name comes from Ancient Greek δίδυμος, meaning "twin", and κέρας, meaning "horn".
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
- Didymoceras binodosum Kennedy and Cobban, 1993
- Didymoceras californicum Anderson, 1958
- Didymoceras cheyenense
- Didymoceras cheyennense
- Didymoceras cochleatus
- Didymoceras hidakense Shigeta in Shigeta et al., 2016
- Didymoceras hornbyense
- Didymoceras navarroensis
- Didymoceras nebrascense Meek and Hayden, 1856)
- Didymoceras newtoni
- Didymoceras nicolletii
- Didymoceras platycostatum Kennedy and Cobban, 1993
- Didymoceras stevensoni
- Didymoceras subtuberculatum Howarth, 1965
- Didymoceras tenuicostatus
- Didymoceras tortus
- Didymoceras tricostatus
- Didymoceras umbilicatu
- Didymoceras uncus
- ''Didymoceras vespertinus''