Just a few steps from the stromatolites, you can find trilobites, which are among the oldest animals on Earth. These critters evolved during the Cambrian Period, starting around 500 million years ago. Because they had a hard exoskeleton, some of them are preserved in amazing detail, even after half a billion years.
Trilobites were a very diverse group of extinct marine arthropods. They first appeared in the fossil record in the Early Cambrian (521 million years ago) and went extinct during the Permian mass extinction (250 million years ago). They were one of the most successful of the early animals on our planet with over 25k described species, filling nearly every evolutionary niche. Due in large part to a hard exoskeleton (shell), they left an excellent fossil record.