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What were the major extinction events of the Devonian Period?
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Devonian Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the early Devonian Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
The Devonian Period (419.2 million to 359 million years ago) was marked by a series of mass extinction events that eliminated 70 to 80 percent of all animal species. These events are often associated with widespread anoxic sedimentation in marine environments.12
The most significant extinction episodes include:
- Lower Zlichov Event: Occurred at the beginning of the Emsian Stage; it led to the extinction of graptoloids and the emergence of goniatites.12
- Taghanic Event: A major extinction period for goniatites, corals, and brachiopods that formerly defined the Middle-Upper Devonian boundary.12
- Kellwasser Event: Occurring at the Frasnian-Famennian boundary, this event caused the loss of many conodont species, most colonial corals, several trilobite groups, and specific brachiopods.12
- Hangenberg Event: Occurred at the end of the Famennian Stage, resulting in the extinction of phacopid trilobites and clymeniid cephalopods.12
While causes remain debated, scientists point to a combination of stresses, including global warming or cooling, bolide impacts, and nutrient runoff from land plants that triggered oceanic oxygen depletion.12