Ancient marine life refers to the diverse organisms that lived in the oceans millions of years ago. This includes creatures like trilobites, ammonites, and early fish. Fossils found in sedimentary rocks provide valuable insights into their anatomy, behavior, and the environments they inhabited. During the Cambrian period, around 541 million years ago, marine life began to flourish, leading to the development of complex ecosystems. Coral reefs emerged, providing habitats for various species. Over time, ancient marine life evolved, giving rise to modern marine species we see today, such as sharks and whales.