Ichthyosaurs were marine reptiles that lived during the Mesozoic Era, primarily from the Triassic to the Cretaceous periods. They resembled modern-day dolphins and were well-adapted to life in the ocean, with streamlined bodies and long snouts. Ichthyosaurs could grow up to 20 feet long and were known for their large eyes, which helped them see in deep water. These creatures were not dinosaurs but belonged to a separate group of reptiles. Ichthyosaurs primarily fed on fish and cephalopods, using their sharp teeth to catch prey. Fossils of ichthyosaurs have been found in various parts of the world, providing valuable insights into their evolution and lifestyle.