The Base of the Cambrian: Small Shelley fauna

[ smalshel ]

The base of the Cambrian period is defined as the appearance of the first animals with hard parts. This picture shows some of the fossils that define the beginning of the Cambrian. They include archaeocyathids, sponge-like early reef-formers, in the first two rows. Inarticulate brachiopods and molluscs are on the bottom row.

Evolution of the Earth, 1994 edition.