''Paractinoceras'' is a genus of long straight slender

actinocerid The Actinocerida are an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposit ...

nautiloid Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species ...

with siphuncular segments in the early stages like those of ''

Actinoceras ''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 U ...

'', becoming narrower in the later stages of the chambered phragmocone like those in '' Ormoceras''. As with ''

Kochoceras ''Kochoceras'' is an extinct nautiloid genus from the later Ordovician belonging to the family Actinoceratidae and found in North America. Morphology ''Kochoceras'' is relatively short, breviconic, and grew to be fairly large with a shell more ...

'' and '' Floweroceras'' ''Paractinoceras'' is considered a separate genus within the

Actinoceratidae The Actinoceriatidae are a family of actinocerids named by Saemann in 1853 for those that grew to have large shells with blunt apices and large siphuncles with widely expanded segments and a generally arcuate endosiphucular canal system.Teicher ...

, distinct from ''

''.

References

* Flower R.H 1968, The First Great Expansion of the Actinoceroids, New Mexico Bureau of Mines and Mineral Resources Memoir 19 Part I, Socorro NM * Actinocerida Prehistoric nautiloid genera Paleozoic life of Manitoba Paleozoic life of the Northwest Territories Paleozoic life of Nunavut {{paleo-nautiloidea-stub