Pangea 250 million years ago, exactly the same as today!
Researchers have long believed that massive volcanic eruptions in present-day Siberia - or possibly a huge meteorite strike - triggered the so-called PermianTriassic extinction. But the precise mechanism of death for so many species remains a subject of debate, with some scientists convinced it was a resulting lack of oxygen in the Earth's oceans or a greenhouse-gas nightmare that nearly ended all plant and animal life.
Runaway ocean acidification "would definitely have a very serious biological impact on ocean calcifiers," said Montenegro, referring to creatures that manufacture their own bodily structures from minerals found in ocean water.
This is an inside joke for geologists. Do not attempt to understand it!