Phragmocone

The cuttlebone ( Endbetonung, " chambered cone ") is the chambered portion of the shell of cephalopods.

The convoluted outer shell original cephalopods, the nautilus ( Nautiloidea ) and the extinct ammonites, consists of a living chamber in which the animal lives, and the chambered cuttlebone.

The cuttlebone is divided by septa ( septa ) into smaller chambers. The Perlbooten these chambers are traversed by a long process, the Siphunculus ( Sipho ), gas- filled and serve the regulation of buoyancy, while their function is not clear in the non- closely related ammonites. The shells of ammonites had thicker walls than those of the nautilus, so that they would not be able to float through the air charge.

In the fossil belemnites of the chambered cuttlebone forms the central part of the extended inner skeleton and lies between the interpreted as a reduced living chamber, tongue- to rod-shaped Proostrakum and the massive rostrum ( thunderbolt ).

The inner shell of the post croissant ( Spirula Spirula ) is chambered, just as there is a chambering in the Schulpen the cuttlefish.