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First record of the leptonectid ichthyosaur Eurhinosaurus longirostris from the Early Jurassic of Switzerland and its stratigraphic framework

Reisdorf, Achim ; Maisch, Michael ; Wetzel, Andreas

In: Swiss Journal of Geosciences, 2011, vol. 104, no. 2, p. 211-224

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    Titre
    • First record of the leptonectid ichthyosaur Eurhinosaurus longirostris from the Early Jurassic of Switzerland and its stratigraphic framework
    Auteur
    • Reisdorf, Achim. Geologisch-Paläontologisches Institut, Universität Basel, Bernoullistrasse 32, 4056, Basel, Switzerland
    • Maisch, Michael. Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191, Stuttgart, Germany
    • Wetzel, Andreas. Geologisch-Paläontologisches Institut, Universität Basel, Bernoullistrasse 32, 4056, Basel, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • Swiss Journal of Geosciences, 2011, vol. 104, no. 2, p. 211-224. SP Birkhäuser Verlag Basel
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:317671
    Summary
    An incomplete skull of the leptonectid ichthyosaur Eurhinosaurus longirostris found in the Rietheim Member (previously "Posidonienschiefer”; Toarcian, Early Jurassic) of Staffelegg, Canton Aargau, is the first record from Switzerland of this taxon and supports the status of Eurhinosaurus longirostris as a palaeobiogeographic very widespread ichthyosaur species in the Early Toarcian of Western Europe. Being from either the Bifrons or Variabilis zone, it is one of the youngest records of Eurhinosaurus and one of the few diagnostic ichthyosaur finds from this time interval. The partial skull is well articulated and preserved three-dimensionally in a carbonate concretion. Both the mode of preservation of the ichthyosaur and an associated ammonoid (Catacoeloceras raquinianum) provided the age of the concretion, which had been collected from scree. Taphocoenosis and taphonomy show the C. raquinianum to be one of few non re-worked fossils recorded from the Early to Late Toarcian boundary (Bifrons/Variabilis zone) of northern Switzerland in general and of this ammonite species in particular. The Toarcian section at Staffelegg differs from other localities where strata of the same age are exposed with respect to facies variations of the Rietheim Member (previously "Posidonienschiefer”, Early Toarcian) and the extraordinarily high thickness of the Gross Wolf Member (previously "Jurensis-Mergel”, Late Toarcian)