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Paläontologische Zeitschrift

, Volume 73, Issue 3–4, pp 277–288 | Cite as

Hydrostatics of fossil ectocochleate cephalopods and its significance for the reconstruction of their lifestyle

  • Klaus Ebel
Article

Abstract

The importance of hydrostatics for ectocochleate cephalopods and for the reconstruction of their lifestyle as well as the implications of hydrostatics and further physical conditions for the ontogenetic shell formation process are discussed. The method used by some authors of merely assuming neutral buoyancy is criticized as not allowable, since even in case of the theoretically possible condition of neutral buoyancy the obligatory vertical shell orientation in orthoconic forms would definitely preclude a horizontal swimming capability. The often presumed neutral buoyancy follows from an old misunderstanding with regard to the original function of the phragmocone, which was modified and amplified only in the course of evolution. The idea of a benthic lifestyle of fossil ectocochleate cephalopods in a gastropod-like fashion is maintained and extended to further palaeozoic forms.

Keywords

Shell Shape Neutral Buoyancy Body Chamber Ammonite Shell Shell Orientation 
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.

Kurzfassung

Die Bedeutung hydrostatischer Gesetze für Schalencephalopoden und für die Rekonstruktion ihrer Lebensweise sowie die Auswirkungen von Hydrostatik und weiteren physikalischen Bedingungen auf die ontogenetische Gehäusebildung werden diskutiert. Die von manchen Autoren benutzte Methode der einfachen Voraussetzung von nicht erwiesener Schwebefähigkeit wird als unzulässig kritisiert, da selbst bei einem theoretisch möglichen Schwebezustand orthokoner Formen die dann zwingend erforderliche vertikale Ausrichtung des Gehäuses der Möglichkeit schwimmender Lebensweise entgegensteht. Die bisher oft vermutete Schwebefähigkeit fossiler Formen beruht auf einem alten Mißverständnis bezüglich der ursprünglichen Funktion des Phragmokons, die erst im Lauf der Evolution abgewandelt und erweitert wurde. Die Vorstellung benthisch lebender fossiler Schalencephalopoden mit gastropodenähnlicher Gehäusestellung wird aufrecht erhalten und auf weitere paläozoische Formen ausgedehnt.

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Copyright information

© E. Schweizerbart’sche Verlagsbuchhandlung 1999

Authors and Affiliations

  • Klaus Ebel
    • 1
  1. 1.MarkdorfGermany

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