The Devonian period closed with multiple mass extinction events. The 2 most severe were the Kellwasser Event 372 million years ago (MYA) and the Hangeberg Event, which ended the Devonian 359 MYA.
The Kellwasser Event, commonly called the “Late Devonian” extinction event, has been known for decades as a major mass extinction event. That the latter Hangeberg Event may have been just as extensive has only recently been discovered.
The Hangeberg Event wiped out many plants and vertebrates, including most tetrapods: the 2-limbed fish that had begun to evolve fingers and toes. Only 5-toed tetrapods survived the Devonian.
It was long thought – before mankind had shown itself an extinction force – that there were just 2 ways to wipe out life on Earth: a bashing bolide or massive volcanism. The Kellwasser Event had several factors. Volcanism was one of them. But the end-Devonian Hangeberg Event lacked both a strike from space and extinctive eruptions.
What the Hangeberg Event had was wrenching climate change, capped by rapid global warming. Oceanic anoxia drove marine extinction. The hotting up also intensified summer thunderstorms, which likely injected an ozone-depleting salts into the stratosphere. The extra ultaviolet decimated forests, resulting in nutrient runoff into the seas which caused massive algae blooms. This furthered warming in a runaway feedback loop.
The Hangeberg Event probably portends what is happening now, in the extinction event which ends human history.
Ishi Nobu, The Elements of Evolution, BookBaby (2019).
John E.A. Marshall et al, “UV-B radiation was the Devonian-Carboniferous boundary terrestrial extinction kill mechanism,” Science Advances (27 May 2020).
Paul Voosen, “UV radiation blamed in ancient mass extinction,” Science (29 May 2020).