The Oldest Fossil

It is probable that all living multicellular animals shared a single common ancestor. Molecular data provide widely divergent results, but suggest that this common ancestor arose between 1 and 1.6 billion years ago. The fossil record of metazoans is more recent, and older fossils are sometimes regarded with suspicion by experts. The oldest common and widely accepted metazoans are members of the Ediacaran fauna, found in rocks dated at between 565 and 543 million years old.

The Ediacaran fauna represents the oldest, well known, diverse set of multicellular organisms, They are found almost worldwide, distributed in rocks from just above the tillites of the last Precambrian glaciation to the Precambrian - Cambrian boundary, and possibly beyond!

The fauna is entirely soft bodied and contains up to 30 species of organisms. The lack of hard parts means that the animals were probably fossilized close to where they lived, as the dead bodies would have been too frail to have been transported for any significant time or distance. If this is, indeed, the case.. then the fossil assemblages represent the beginning of ecosystems.