Fossil of a trilobite
The structure of a trilobite, including the antennae and legs, can be seen in the Burgess Shale, a rock formation found in the Canadian Rockies in 1909.
This trilobite lived some 505 million years ago. Trilobites were a class of ocean-dwelling artrhopods that first emerged some 540 million years ago and became extinct at the end of the Permian period 250 million years ago. Trilobites had a hard exoskeleton made of minerals, and these exoskeletons were frequently preserved as fossils. Scientists have identified some 17,000 species of trilibites from the fossil record.
The Burgess Shale contains a vast fossil record that provided the first glimpse into the diverse animal life of the Cambrian Period (542-488 million years ago).