The Cambrian explosion
Almost every animal group appears at once
See it on the timeline →In depth
The Burgess Shale in Canada and Chengjiang in China preserve soft tissue from animals such as trilobites and Anomalocaris in astonishing detail. The causes are debated: rising oxygen, more dissolved calcium, the evolution of Hox genes that govern body plans, and above all the start of an evolutionary arms race between predator and prey. Eyes are a key — once something can see you, it pays to hide, to grow a shell and to move faster.
For children
In just a few million years — lightning fast in Earth's history — the ocean filled with brand new animals. They developed eyes, shells, legs and jaws. Almost every animal group alive today appeared in this period.
Connects to
Part of Terra Saga — the story of Earth on a timeline. terrasaga.org