Anapsida is 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, which are believed to have diverged early in the evolutionary history of reptiles. Anapsids are distinct from other reptilian groups, such as Diapsida, which have two temporal fenestrae. The evolutionary significance of anapsids lies in their unique adaptations and the role they play in understanding the development of reptiles over time. Their fossil record provides insights into the early diversification of reptiles.