542 million years ago the Cambrian period began, it ended 488 million years ago.
All life still exists in the ocean, nothing has yet set foot on the land. Oxygen is increasing in the atmosphere, thanks to our cyanobacteria. This is still the only plant life on the planet. The increased oxygen from our stromolites is very likely the reason for the explosion of animal life in this era.
There are large numbers of marine invertebrates. Animals are diversifying, multiplying and evolving in leaps and bounds including herbivores. Because of this there is a decline in the amount of stromolites being carried in the seas.
The seas are rising and washing over continents of Gondwana, Laurentia, and Baltica. Seas are shallow. The climate has warmed and the world is very wet, and very mild in temperature.