Ammonoid Buoyancy

Abstract

The buoyancy of ammonoids is one of the most controversial issues of ammonoid paleobiology. This chapter gives a short historical review about attempts made to clarify the potential function of the cephalopod chambered shell (phragmocone) and ammonoid life habits either as benthic crawler or as free swimmers in the water column. In order to understand efficiency of buoyancy control and the mode of life of the extinct ammonoids decoupling of cameral liquid, process of osmotic pumping including local osmosis, pre-septal gas, and the role of the siphuncle and cameral liquid were discussed extensively. It is accepted that processes like osmotic pumping and local osmosis act in ammonoids due to similar architecture of the extant relatives including the presence of a siphuncle. Additionally, the calculation of buoyancy represents a major task which depends on exact reconstructions of volumes and densities for shell and soft body. With the rise of 3D-imaging techniques the determination of volumes were enhanced and now represent an important step towards more precise buoyancy calculations.