Eocene-Oligocene Extinction Event

The Eocene-Oligocene extinction event, also called the Grande Coupure, occurred about 33.9 to 33.4 million years ago at the boundary between the two epochs. It was relatively minor compared to the largest mass extinctions but still involved substantial species loss and faunal turnover, driven mainly by the glaciation of Antarctica and the start of the Late Cenozoic Ice Age, itself brought on by a decline in atmospheric carbon dioxide as the Indian subcontinent drifted into equatorial latitudes and the Deccan Traps weathered. Temperatures in central North America fell by roughly 8.2 degrees Celsius over about 400,000 years. In Europe, many endemic mammal groups disappeared while Asian species immigrated, producing markedly different faunas before and after the event, and marine ecosystems saw shark diversity decline even as some fish groups diversified rapidly.