| Actinoceras Temporal range: M Ordovician - L Silurian
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| Cast of a specimen discovered at the Newbury Marble Works, Derbyshire, England that is part of the OUMNH coll. | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Order: | †Actinocerida |
| Family: | †Actinoceratidae |
| Genus: | †Actinoceras Bronn, 1885 |
Actinoceras is the principal and root genus of the Actinoceratidae, a major family in the Actinocerida, that lived during the Middle and Late Ordovician. It is an extinct genus of nautiloid cephalopod that thrived in the warm waters of the United States and England during the Paleozoic era.