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Septal complexity in ammonoid cephalopods increased mechanical risk and limited depth

Published online by Cambridge University Press:  08 February 2016

Thomas L. Daniel ,
Brian S. Helmuth ,
W. Bruce Saunders  and
Peter D. Ward
Thomas L. Daniel
Affiliation:
Department of Zoology, University of Washington, Box 351800, Seattle, Washington 98195-1800. E-mail: danielt@zoology.washington.edu
Brian S. Helmuth
Affiliation:
Department of Zoology, University of Washington, Box 351800, Seattle, Washington 98195-1800. E-mail: helmuthb@zoology.washington.edu
W. Bruce Saunders
Affiliation:
Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010. E-mail: wsaunder@brynmawr.edu
Peter D. Ward
Affiliation:
Department of Geological Sciences, University of Washington, Box 351310, Seattle, Washington 98195-1310. E-mail: argo@u.washington.edu
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Abstract

The evolution of septal complexity in fossil ammonoids has been widely regarded as an adaptive response to mechanical stresses imposed on the shell by hydrostatic pressure. Thus, septal (and hence sutural) complexity has been used as a proxy for depth: for a given amount of septal material greater complexity permitted greater habitat depth. We show that the ultimate septum is the weakest part of the chambered shell. Additionally, finite element stress analyses of a variety of septal geometries exposed to pressure stresses show that any departure from a hemispherical shape actually yields higher, not lower, stresses in the septal surface. Further analyses show, however, that an increase in complexity is consistent with selective pressures of predation and buoyancy control. Regardless of the mechanisms that drove the evolution of septal complexity, our results clearly reject the assertion that complexly sutured ammonoids were able to inhabit deeper water than did ammonoids with simpler septa. We suggest that while more complexly sutured ammonoids were limited to shallower habitats, the accompanying more complex septal topograhies enhanced buoyancy regulation (chamber emptying and refilling), through increased surface tension effects.

Type
Articles
Information
Paleobiology , Volume 23 , Issue 4 , Fall 1997 , pp. 470 - 481
Copyright
Copyright © The Paleontological Society 

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References

Literature Cited

Boyajian, G., and Lutz, T. 1992. Evolution of biological complexity and its relation to taxonomic longevity. Geology 20:983–986.2.3.CO;2>CrossRefGoogle Scholar
Buckland, W. 1836. Geology and mineralogy considered with reference to natural theology. Treatise VI. The Bridgewater treatise on the power, wisdom, and goodness of god as manifested in the Creation. W. Pickering, London.Google Scholar
Cook, R. D. 1981. Concepts and applications of finite element analysis. Wiley, New York.Google Scholar
Denton, E. J., and Gilpin-Brown, J. B. 1966. On the buoyancy of the pearly Nautilus. Journal of the Marine Biological Association of the United Kingdom 46:723–759.CrossRefGoogle Scholar
Denton, E. J., and Gilpin-Brown, J. B. 1973. Flotation mechanisms in modern and fossil cephalopods. Advances in Marine BiologyCrossRefGoogle Scholar
Fung, Y. C. 1981. Biomechanics: mechanical properties of living tissues. Springer, New York.CrossRefGoogle Scholar
Henderson, R. 1984. A muscle attachment proposal for septal function in Mesozoic ammonites. Paleontology 27:461–468.Google Scholar
Hewitt, R. A., and Westermann, G. E. G. 1986. Function of complexly fluted septa in ammonoid shells. I. Mechanical principles and functional models. Neues Jahrbuch für Geologie und Paläontologie 172:47–69.CrossRefGoogle Scholar
Hewitt, R. A., and Westermann, G. E. G. 1987a. Function of complexly fluted septa in ammonoid shells. II. Septal evolution and conclusions. Neues Jahrbuch für Geologie und Paläontologie 174:135–169.Google Scholar
Hewitt, R. A., and Westermann, G. E. G. 1987b. Nautilus shell architecture. Pp. 435–416 in Saunders, W. B. and Landman, N. H., eds. Nautilus: the biology and paleobiology of a living fossil. Plenum, New York.Google Scholar
Jacobs, D. 1990. Sutural patterns and shell stresses in Baculites with implications for other cephalopod shell morphologies. Paleobiology 16:336–348.CrossRefGoogle Scholar
Jacobs, D. 1996. Chambered cephalopod shells, buoyancy, structure and decoupling: history and red herrings. Palaios 11:610–614.CrossRefGoogle Scholar
Kulicki, C., and Mutvei, H. 1988. Functional interpretation of ammonoid septa. Pp. 215–228in Weidmann, J. and Kullmann, J., eds. Cephalopods present and past. Schweizerbart, Stuttgart.Google Scholar
MARC. 1996. Finite Element Solver, Version K6.2. MARC Analysis Research Corporation, Palo Alto, Calif.Google Scholar
Mutvei, H. 1975. The mode of life in ammonoids. Paläontologische Zeitschrift 49:196–201.CrossRefGoogle Scholar
Newell, N. 1949. Phyletic size increase, an important trend illustrates by fossil invertebrates. Evolution 3:103–124.CrossRefGoogle ScholarPubMed
Pfaff, E. 1911. Über form und bau der Ammonitenseptum und ihre beziehungen zur sututlineai. Jahresbericht Niedersachsen geologische Vereins, Hannover 4:207–223.Google Scholar
Saunders, W. B. 1995. The ammonoid suture problem: relationships between shell and septum thickness and suture complexity in Paleozoic ammonoids. Paleobiology 21:343–355.CrossRefGoogle Scholar
Saunders, W. B., and Work, D. M. 1996. Shell morphology and suture complexity in Upper Carboniferous ammonoids. Paleobiology 22:189–218.CrossRefGoogle Scholar
Seilacher, A. 1975. Mechanische simulation und funktionelle evolution des ammoniten-septums. Paläontologische Zeitschrift 49:268–286.CrossRefGoogle Scholar
Seilacher, A. and LaBarbera, M. 1995. Ammonoids as cartesian divers. Palaios 10:493–506.CrossRefGoogle Scholar
Spath, L. 1919. Notes on ammonites. Geological Magazine 56:27–35.CrossRefGoogle Scholar
Vincent, J. 1990. Structural biomaterials. Princeton University Press, Princeton, N.J.Google Scholar
Wainwright, S. A., Biggs, W. D., Currey, J. D., and Gosline, J. M. 1982. Mechanical design in organisms. Princeton Univeristy Press, Princeton, N.J.CrossRefGoogle Scholar
Ward, P. D. 1987. The natural history of Nautilus. Allen and Unwin, Boston.Google Scholar
Ward, P. D., and von Boletzky, S. 1984. Shell implosion depth and implosion morphologies in three species of Sepia (Cephalopoda) from the Mediterranean Sea. Journal of the Marine Biological Association of the United Kingdom 64:955–966.CrossRefGoogle Scholar
Westermann, G. E. G. 1971. Form, structure and function of shell and siphuncle in coiled Mesozoic Ammonoids. Life Sciences Contributions, Royal Ontario Museum 78:1–39.Google Scholar
Westermann, G. E. G. 1975. Model for origin, function, and fabrication of fluted cephalopods septa. Paläontologische Zeitschrift 49:235–253.CrossRefGoogle Scholar