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(class Cephalopoda, subclass Nautiloidea)

A large order of predominantly orthoconic cephalopods that have large siphuncles. Large amounts of siphuncular and cameral deposits are present. Most are assumed to have been nektonic. The actinoceratids ranged in age from Early Ordovician to lower Carboniferous.

Subjects: Zoology and Animal Sciences.

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