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Calculation and simulation of ammonoid hydrostatics

Published online by Cambridge University Press:  08 April 2016

W. Bruce Saunders
Affiliation:
Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010
Earl A. Shapiro
Affiliation:
Department of Natural Resources, 19 Martin Luther King Drive SW, Atlanta, Georgia 30334

Abstract

The buoyancy, stability, and orientation of a shelled cephalopod in water are the predictable products of shell geometry, body chamber length, and such physical parameters as shell, tissue, and water densities. Given such physical characteristics as shell geometry, shell, tissue, and water densities, and shell thickness, the hydrostatic characteristics of planispiral shelled cephalopods, including orientation, centers of mass and buoyancy, stability, and neutrally buoyant body chamber length, can be calculated and simulated using microcomputer-based techniques. Individual variables such as geometry, body chamber length, and shell thickness are linked in a calculable manner to orientation, neutral buoyancy, and stability. Living Nautilus provides a means of testing the model and for making hydrostatic comparisons between ammonoids and nautiloids. The close agreement between calculated versus observed body chamber lengths in five species of Mississippian ammonoids shows that neutral buoyancy, and (with one exception) Nautilus-like orientations, were at least feasible for these species.

Type
Articles
Copyright
Copyright © The Paleontological Society 

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References

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