Until Now
Biology

The dinosaurs inherit the Earth

Their rivals are wiped out, and within a few million years dinosaurs dominate every large-animal niche.

When
Known to
± 1 million years
Era
Jurassic, Mesozoic

The crocodile-line archosaurs that had outnumbered and outcompeted dinosaurs for thirty million years are almost entirely destroyed at the end of the Triassic; dinosaurs pass through comparatively unscathed. Why is unresolved — possibly respiratory physiology, possibly insulation, possibly luck. Whatever the reason, the Jurassic opens with dinosaurs unopposed, and they hold that position for 135 million years.

Just before

Just after