References

Journal of Micropalaeontology

J. Micropalaeontol.

2041-4978

GSL Publishing

Göttingen, Germany

10.1144/jm.10.2.151

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

Siveter

David J.

⁰ Vannier

Jean M. C.

¹ Palmer

Douglas

Dept. of Geology, University of Leicester, LE1 7RH, U.K.

Centre des Sciences de la Terre, Université Claud Bernard, Lyon 1, France.

Dept. of Geology, Trinity College, Dublin 2, Ireland, (current address: Department of Geology, National Museum of Wales, Cardiff CF1 3NP, UK.)

01 12 1991

10 2 151 173

1991

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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.<br/><br/>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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