Introduction to the Primitive Marine Life Hall: The Marine Life Hall shows visitors various fossils of the ocean, which can be traced back to the Cambrian explosion of life in the ocean world 570 million years ago. Animals that had never been seen on earth suddenly appeared in the ocean like a "big bang". Trilobites of various shapes appeared. It is a kind of marine arthropod and is the ancestor of modern crabs, lobsters and insects. Distant relatives, the entire reproduction process has taken 300 million years, and there are more than 10,000 varieties.