The ichthyosaur was a marine reptile that lived during the Mesozoic Era, primarily in the Jurassic and Cretaceous periods. These creatures resembled modern-day dolphins and were well-adapted to life in the ocean, with streamlined bodies and large eyes. Ichthyosaurs were not dinosaurs but were part of a separate group of reptiles that evolved to thrive in aquatic environments. Ichthyosaurs varied in size, with some species reaching lengths of over 20 feet. They primarily fed on fish and cephalopods, using their sharp teeth to catch prey. Fossils of ichthyosaurs have been found in many parts of the world, providing valuable insights into their biology and the ecosystems of ancient oceans.