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Journal of Micropalaeontology An open-access journal of The Micropalaeontological Society
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Volume 10, issue 2
J. Micropalaeontol., 10, 151–173, 1991
https://doi.org/10.1144/jm.10.2.151
© Author(s) 1991. This work is distributed under
the Creative Commons Attribution 4.0 License.
J. Micropalaeontol., 10, 151–173, 1991
https://doi.org/10.1144/jm.10.2.151
© Author(s) 1991. This work is distributed under
the Creative Commons Attribution 4.0 License.

  01 Dec 1991

01 Dec 1991

Silurian Myodocopes: Pioneer pelagic ostracods and the chronology of an ecological shift

David J. Siveter1, Jean M. C. Vannier2, and Douglas Palmer3 David J. Siveter et al.
  • 1Dept. of Geology, University of Leicester, LE1 7RH, U.K.
  • 2Centre des Sciences de la Terre, Université Claud Bernard, Lyon 1, France.
  • 3Dept. of Geology, Trinity College, Dublin 2, Ireland, (current address: Department of Geology, National Museum of Wales, Cardiff CF1 3NP, UK.)

Abstract. Analysis of all relevant palaeontological and global geological data strongly supports the notion that representatives of Silurian myodocope ostracods had pelagic lifestyles and habitats and that they may well be, within the Ostracoda, pioneer colonisers of such environments. Morphological evidence (from fossil and Recent myodocopes) combined with facies distributional and concomitant faunal evidence (from the Silurian of, for example, Britain, France, Czechoslovakia, Sardinia, Australia and China) endorses the idea that myodocope ostracods may have undergone a benthic to pelagic ecological shift during mid Silurian times.

Lower Silurian myodocopes lived, with benthic associates, on well oxygenated shelves. Upper Silurian ostracods lived, typically with low diversity, largely pelagic faunas in outer shelf topographic lows or off-shelf basin slopes, and are characteristically associated with deposits which are in part suggestive of lowered oxygen levels or even anoxic conditions. A pre-adaptation for swimming may have allowed Silurian myodocopes to respond to environmental forcing (negative oxygen levels; positive trophic and nutrient incentives; rises in sea levels) by migrating, through time, up the water column.

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