Olson's Extinction
A little-known crisis clears out the sail-backed synapsids and hands the land to our own ancestors.
- When
- Known to
- ± 3 million years
- Era
- Permian, Paleozoic
Around 273 million years ago terrestrial vertebrate diversity drops sharply and takes millions of years to recover. The pelycosaur-grade synapsids that had dominated are largely eliminated, and the vacancy allows the therapsids — a more advanced synapsid group, with legs beneath the body rather than sprawled — to radiate. Without it the mammal lineage might never have got started.