The evolution of multicellular life

The earliest definite fossils of multicellular animals (Metazoa) come from the Ediacaran deposits in Australia; these, and similar deposits elsewhere in the world, date to the period from 670 to 550 million years ago.

The Ediacarian fossils are of soft-bodied aquatic animals such as jellyfish and worms. Most or all of them went extinct before the beginning of the Cambrian period about 550 million years ago. The Cambrian sees a great increase in the diversity and numbers of fossils - so much so that the main time periods of the fossil record begin with Cambrian.

The image opposite is of a Cambrian worm Ottoia prolifica from the celebrated Burgess Shale collection. This collection contains an enormous variety of soft-bodied multicellular organisms.