Cephalopods, ancestors of modern nautiluses, octopuses, squids, and cuttlefish, were well-developed and became dominant marine predators after the decline of trilobites. Some cephalopods grew to impressive sizes, up to fifteen feet long. During this era, over a thousand species of ammonites evolved on the Pacific coast of California, showcasing the diversity and evolutionary advancements of cephalopods. These creatures thrived as masters of the seas during significant transitional periods in Earth's history. [1]