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Paläontologische Zeitschrift

, Volume 49, Issue 3, pp 235–253 | Cite as

Model for origin, function and fabrication of fluted cephalopod septa

  • G. E. G. Westermann
Article

Abstract

The model supposes that sub-hemispheric septa of deep-water cephalopods evolved transverse pillars by meridional fluting in order to support flat and therefore weak areas of the shell wall. Several trends toward reduction of sutural spacing for improved wall support resulted in rise of fluting and finally, marginal crenulation. During ontogeny, the function of the ammonite septum as complex vault system against ”normal“ pressure from the body was succeeded by compound-pillar function for wall support. Fabrication of ammonitic septa probably involved positive pressure differential of new ”cameral“ liquid, orientation of mantle fibers along stress lines, and successively affixed tie-points which lay on an aponeurosislike mantle structure.

Keywords

Shell Wall Stress Line Royal Ontario Museum Septal Neck Septal Curvature 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Zusammenfassung

Das Modell nimmt an, daß subhemisphärische Septen von Tiefsee-Cephalopoden phylogenetisch transversale Pfeiler durch meridionale »Faltung« (fluting) entwickelten, um flache und daher schwache Teile der Schalenwand zu unterstützen. Mehrere Trends zur Verminderung des Suturabstandes für verbesserte Wandabstützungen resultieren in vergrößerter Faltungshöhe und schließlich randlicher Krenulierung des Septums. Das ammonitisene Septum funktionierte ontogenetisch zuerst als komplexes Gewölbe gegen Körperdruck, dann ais Bündelpfeiler für Wandabstützung. Die Fabrizierung des Ammonitenseptums wurde wahrscheinlich durch positiven Druckunterschied der neuen Kammerflüssigkeit, Ausrichtung der Mantelfasern nach den Drucklinien und nacheinander befestigte Haftpunkte entlang einer Aponeurosis-ähnlichen Mantel-Struktur unterstützt.

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Copyright information

© E. Schweizerbart’sche Verlagsbuchhandlung 1975

Authors and Affiliations

  • G. E. G. Westermann
    • 1
  1. 1.Department of GeologyMcMaster UniversityHamiltonCanada

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