Metazoa: Fossil Record

Chart of First Appearances of Metazoans

The chart above shows the oldest undoubted fossil occurences of each of the living major groups of animals. Note how many of the animal groups have fossil records that date back to the Cambrian period, over 500 million years ago. Those groups which do not date back to the Cambrian, with the single exception of the Bryozoa, do not possess mineralized skeletons. It is likely that all major animal groups, even those which have not left us fossils, originated in the Cambrian. This sudden appearance of many major groups of animals is often referred to as the "Cambrian Explosion".

The image above is mapped! We have additional information on the geological time periods along the top of the image. Also, each of the taxonomic groups in pink boxes can be clicked upon to take you to their exhibit in our museum.

UCMP Special Exhibit: Vendian Animals

Ben Waggoner has worked extensively with the troublesome creatures of the Vendian. You can learn about these earliest animals in his exhibit.