The Late Ordovician extinction 443 million years ago struck in two pulses driven by opposite climate extremes: the first came as the planet cooled, glaciers spread and sea levels collapsed; then the ice retreated, the seas warmed and lost their oxygen, killing many of the species that had survived the cold
The Late Ordovician extinction, close to the Ordovician-Silurian boundary about 443 million years ago, is usually read as…
