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TOPIC: Devonian Period


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Clam fossils divulge secrets of ecologic stability

Clam fossils from the middle Devonian era - some 380 million years ago - now yield a better paleontological picture of the capacity of ecosystems to remain stable in the face of environmental change, according to research published today (May 15) in the online journal PLOS ONE.
Trained to examine species abundance - the head counts of specimens - paleontologists test the stability of Earths past ecosystems. The research shows that factors such as predation and organism body size from epochs-gone-by can now be considered in such detective work.
Back 380 million years ago, New York was under the Devonian sea. Today, the fossils found in the rocks of this region have become well-known for documenting long-term stability in species composition - that is, the same species have been found to persist with little change over a 5 million-year period. But research has found that species abundance in this ancient ecosystem went up and down, generating debate among paleontologists about whether the fauna, as a whole, was also stable in terms of its ecology.

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'Toxic sea' led to Devonian extinction

Analysis of a 380-million-year-old crab-like fossil from Western Australia has painted a gruesome picture of the events leading to one of Earth's major mass extinctions. Climate change and a devastating meteorite have both been fingered as causes for the decimation of marine life during the late Devonian period. But research published in a recent issue of the journal Geology suggests the extinction occurred as a result of a toxic ocean, devoid of oxygen.
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Toxic oceans preserve ancient life

Curtin University research showing that bacteria were responsible for the excellent preservation of a crab-like fossil during the Devonian period suggests that organic geochemistry could be a useful new tool for understanding ancient environments.
The research, recently published in the prestigious journal Geology, showed that hydrogen sulphide dependant organisms (known as Chlorobi) and sulphate-reducing bacteria had preserved the shell and the muscles of the crustacean. Their presence proves there was a toxic ocean environment in the Devonian Period, potentially responsible for the mass extinction 380 million years ago.

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In the middle of the Devonian Period some 385 million years ago, the Wissahickon Schist was the heart of a huge mountain chain that was something like the Pacific Northwest of today. Volcanoes formed here and there. The land was subjected to earthquakes and eruptions from time to time.
To the west was a vast epicontinental sea. It was not a true ocean because it formed over continental rock. The climate was warm, probably warmer than today.
We call the mountains the Taconic Mountains. They were formed as Laurentia, now North America, collided with an arc of volcanic islands.

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