Introduction to Ichthyosaurus: Ichthyosaur is a large sea-dwelling reptile similar to fish and dolphins that lived in the Mesozoic Era. It evolved into an ichthyosaur after a certain land-dwelling reptile returned to the sea. This atavism not only exists among reptiles, but also living mammals, dolphins and whales, have also lived on land. Ichthyosaurs appeared and became extinct more than 20 million years earlier than dinosaurs, and they dominated the oceans at that time. The specimens on display on the wall are two ichthyosaurs held together, one of which is 10.6 meters long with a restored head and tail, and the other is 5.1 meters long.