👉 Silurids are a group of marine organisms that have a fossil record dating back to the Cambrian period, approximately 540 million years ago. They are characterized by their large size and complexity in terms of cell structure, organ system organization, and genetic diversity. Silurians were responsible for the majority of the animal life on Earth during this time, making up about 97% of all known marine organisms. This group includes a wide range of animals from microscopic plankton to massive