Considering a supernova as the possible cause of the End Devonian Extinction.
[sciencythoughts.blogspot.com]
The Late Devonian biodiversity crisis is characterized by a protracted decline in speciation rate occurring over millions of years, punctuated by an extinction pulse (Kellwasser event) followed about 10 million years later by a more moderate extinction (Hangenberg event) around the Devonian/Carboniferous Boundary, about 359 million years ago. It has recently been suggested that the Hangenberg event was associated with ozone depletion, in light of evidence such as malformations persisting in palynological assemblages on the order of many thousands of years. It has been argued that volcanic eruption and a large igneous province triggered ozone depletion, whereas other research has instead linked it to an episode of global warming not caused by a large igneous province.