Ichthyosaur, << IHK thee uh sawr, >> was a type of fishlike reptile that is now extinct. Ichthyosaurs lived at about the same time as the dinosaurs. The oldest known ichthyosaur fossils are about 245 million years old. Ichthyosaurs became extinct about 90 million years ago.
Most ichthyosaur species (kinds) had fishlike bodies with four paddle-shaped limbs. They had a triangular fin on the back and a powerful tail fin that moved from side to side. Unlike fish, ichthyosaurs breathed air. They also gave birth to live young. The smallest species of ichthyosaurs were less than 3 feet (1 meter) long. The largest species may have reached over 80 feet (25 meters) long. These were the largest ocean reptiles that ever lived.
Most species of ichthyosaurs were quick predators (hunting animals). They ate squidlike animals, fish, and marine reptiles. Ichthyosaurs had large eyes that enabled them to see prey even in dark waters. One species had huge eyes up to 10 inches (25 centimeters) across.
Despite their appearance, ichthyosaurs were not closely related to fish or dolphins. Instead, they descended from reptiles that lived on land. The resemblance between these animals is an example of convergent evolution. Convergent evolution is the process by which distantly related animals develop similar body shapes because they live in the same type of environment. In this case, fish, dolphins, and ichthyosaurs resemble one another because they all evolved to become streamlined to move easily through the water.
Ichthyosaurs died out about 25 million years before the dinosaurs became extinct. Scientists are not sure why ichthyosaurs went extinct. Possibilities include environmental change or the disappearance of prey. They also may have struggled to compete with bony fish, other marine reptiles, and modern sharks.
