This Marrella specimen shows how clear and detailed the fossils are from the Burgess Shale lagerstätte.

Dickinsonia, an Ediacaran animal with a quilted appearance.

A fossilized trilobite. This specimen of Olenoides serratus, from the Burgess shale, preserves 'soft parts' – the antennae and legs.

The Cambrian is the first geological period of the Palaeozoic era and the Phanerozoic eon. It lasted from 541 million years ago to 485.4 million years ago. Before it came the Ediacaran, and after it the Ordovician.

Biologists have learnt quite a lot about the soft parts of Cambrian animals. This is because places have been found where soft parts of organisms are preserved as well as their more resistant shells. This means our understanding of the Cambrian biota is better than that of some later periods.