Anapsids are a group of reptiles characterized by their skull structure, which lacks temporal fenestrae—openings behind the eyes. This group includes ancient reptiles like turtles and their ancestors. Anapsids are distinct from other reptiles, such as diapsids, which have two temporal fenestrae, and synapsids, which have one. The evolutionary history of anapsids dates back to the late Paleozoic era. They are primarily represented today by turtles, which have adapted to various environments, including land and water. Anapsids play a crucial role in understanding the evolution of reptiles and their diverse adaptations over millions of years.