Severity: 3rd worst
Cause: Still unclear, changes in sea level and ocean anoxia (?)
Climate: Abrupt cooling
Aftermath: Marine filter feeders diversify
Rather similar to the End-Ordovician extinction, warm-water marine invertebrates were the hardest hit during the Late Devonian extinction. 22% of known marine families and 57% of marine genera were wiped out during a global cooling event. Gondwana glaciations were once again the likely culprit, triggering a massive overturn of ocean waters, bringing cold, non-oxygenated bottom waters to the surface. As opposed to a sudden impact event (which will be showing up later), the Late Devonian extinction was characterized by slow glacial cooling. Estimates for this extinction’s duration range from 500,000 yrs to 25 My, so although it was the third most severe, it’s timing is still rather poorly constrained.
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Emily Zawacki, Ph.D. 