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Per Ahlberg, Skottland 2013

Per Ahlberg

Professor emeritus

Per Ahlberg, Skottland 2013

Faunal turnovers and trilobite morphologies in the upper Cambrian Leptoplastus Zone at Andrarum, southern Sweden

Författare

  • Per Ahlberg
  • Kristina Månsson
  • ENK Clarkson
  • CM Taylor

Summary, in English

The Furongian (upper Cambrian) Leptoplastus Zone marks a time of critical changes in the evolution of olenid trilobites. This zone, unexposed at Andrarum in Skane, southern Sweden, has been re-excavated and the sequence of faunas and sediments logged in detail. The faunal succession accords with that previously described from borehole cores by Westergard, and the subzones of L. paucisegmentatus, L. raphidophorus, L. crassicornis, L. ovatus, L. angustatus, and L. stenotus have been recognized. In the first two subzones the olenid assemblages are monospecific. At the base of the L. crassicornis Subzone more than one species is present and morphotypes with long genal spines appear for the first time. Faunal turnover is rapid, but the incoming of new species is invariably linked to an abrupt change in sedimentation, or follows an unfossiliferous interval; species either arose or migrated in after a time of environmental perturbation. Particular faunal associations are often confined to discrete sedimentary packages though some species may range through a succession of sedimentary changes. Leptoplastus crassicornis has very long genal spines, adapted for resting on the sea floor; it may have competed with the coeval, and very similar, L. angustatus. Subsequently, L. angustatus is accompanied by the stout-bodied, short-spined L. ovatus, which presumably occupied a different niche within the same environment. Leptoplastus stenotus is convergent on the much earlier L. paucisegmentatus, and likewise is found as a monospecific assemblage, presumably being adapted to a similar niche.

Avdelning/ar

  • Berggrundsgeologi

Publiceringsår

2006

Språk

Engelska

Sidor

97-110

Publikation/Tidskrift/Serie

Lethaia

Volym

39

Issue

2

Dokumenttyp

Artikel i tidskrift

Förlag

Taylor & Francis

Ämne

  • Geology

Nyckelord

  • Leptoplastus zone
  • Cambrian
  • Andrarum
  • biostratigraphy
  • trilobites
  • Sweden
  • Skane
  • palaeoecology

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0024-1164