Ozone Depletion May Have Caused Prehistoric Extinction Event

Scientists now believe asteroid strikes and volcanic eruptions might not be the only natural triggers for mass extinction.

    2020/05/28

NSFW    SOUTHAMPTON, ENGLAND — Ozone depletion may have triggered a mass die-off of ancient fish and plants by ultraviolet ray exposure 358 million years ago, according to a new study in Science Advances.

Science Magazine reports the research team took a "perfect" six-meter-long mudstone drilled core. Preserved in the sample were spores from land plants that had flourished in the Devonian period, when Greenland was part of the Old Redstone Continent.

According to the study, the fossilized spores showed a transition from healthy, normal spores to malformed and blackened spores. The deformities observed strongly suggest the parent plants suffered DNA damage from high levels of ultraviolet-B rays.

The spores dated to the Late Devonian die-off, the second mass extinction in the period that saw the disappearance of many species, including giant armored sharks. The descendants of the surviving bony fish and sharks would populate today's oceans.

Importantly, the second-wave extinction wiped out the first four-limbed fish that had ventured onto land. This means another group of five-toed tetrapods became the precursor of land animals.
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