The fossil record from 500 to 440 million years ago is one of spectacular diversity, but only at certain locations. Much of life does not fossilise easily: compare how easy it is to find a fossil shell rather than a fossil jellyfish. This means that our knowledge of how some groups of anmals evolved is limited. That is what makes these new fossils from Fezouata in Morocco so important. During the Cambrian and Ordovician periods, evolution was experimenting with wierd and wonderful body plans and it was thought that many of the Cambrian "oddities" did not survive into the Ordovician Period. However, the fossils preserved at Fenzouata show otherwise. These Cambrian animals, which included armoured lobopodian worms and fearsome anomalocarid predators, actually survived for far longer than we previously thought. This paper, documenting the new discoveries at Fenzouata, is the first in a new series for the Geological Society of London. This series seeks to provide a review of current knowledge on exceptional fossil sites that will be freely available to the public, students and scientists alike.