Read: THE CAMBRIAN EXPLOSION A Big Bang In The Evolution of Life from the Shape of Life book.
The Cambrian explosion was a period (540mya to 515mya) when animal life diversified rapidly. It was a time when the continents were very different from today. Here is a short article
Readings for Cambrian Explosion
We created readings on various aspects of the Cambrian Explosion. Below are links to those documents.
Stephen Jay Gould wrote a very readable book about the Cambrian Explosion. Here is a review of the book.
Ray Troll has created this fun graphic of the geologic time scale.