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Paläontologische Zeitschrift

, Volume 60, Issue 3–4, pp 255–275 | Cite as

The type species of the ordovician trilobitesymphysurus: systematics, functional morphology and terrace ridges

  • R. A. Fortey
Article

Abstract

The type of the widespread Ordovician trilobiteSymphysurus, S. palpebrosus Dalman, 1827, is redescribed from the type Swedish material; its distribution is documented.Symphysurus is one of very few trilobite genera to be found in both Ordovician Baltica and Gondwana, in more peripheral sites relative to the platform areas.S. palpebrosus has complex coaptative devices to ensure tight enrollment. Analysis of the functional morphology shows that it spent at least part of its life with thorax and pygidium buried in the sediment in the bumastoid stance, although it may have fed outside its burrow. Terrace ridges are well developed on certain parts of the cuticle; their positioning and geometry shows that only a few of them could have functioned in direct engagement with the sediment. Those associated with petaloid thoracic facets may have permitted respiration in the enrolled condition.

Keywords

Ordovician Thoracic Segment Biofacies Cephalon Internal Mould 
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 Typusart der ordo vizischen Trilobiten-GattungSymphysurus, S. palpebrosus Dalman 1827, wird anhand des schwedischen Typusmaterials neu beschrieben. Die Gattung tritt, verglichen mit der damals meist engeren geographischen Bindung anderer Trilobiten, in auffallend weiter Verbreitung auf, namlich sowohl in peripheren Bereichen des Skandinavischen Paläokontinents als auch des (heute südeuropäisch-vorderasiatischen) Gondwana-Nordsaums, und zwar in relativ bathyaler Fazies.

S. palpebrosus besitzt an enge Einrollung angepaßte Organisationsmerkmale. Die funktionsmorphologiscne Analyse zeigt, daß sich diese Art zeitweilig in bumastoider Stellung, also mit eingegrabenem Pygidium und Thorax, aber freiem Cephalon im Sediment aufhielt, der Nahrungssuche aber außerhalb ihres Baus nachgegangen sein dürfte. Die Funktion der auf manchen Partien der Cuticula wohl ausgebildeten Terrassenlinien ist noch immer ein in mancher Hinsicht offenes Problem. Ihre Stellung, Lage und Anordnung zeigen, daß nur einige davon mit dem Eingraben in das Sediment zu tun hatten. Soweit sie mit petaloiden Thoraxfacetten gekoppelt sind, könnten sie die im eingerollten Zustand herabgesetzte Atmung gewahrleistet haben.

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Copyright information

© E. Schweizerbart’sche Verlagsbuchhandlung 1986

Authors and Affiliations

  • R. A. Fortey
    • 1
  1. 1.British Museum (Natural History)LondonEngland

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