Diapsids are a group of reptiles characterized by having two temporal fenestrae, which are openings in the skull behind the eyes. This group includes modern reptiles like crocodiles, lizards, and birds, as well as extinct species such as dinosaurs. Diapsids are known for their diverse adaptations and evolutionary success in various environments. The diapsid lineage is significant in the history of life on Earth, as it gave rise to many dominant terrestrial vertebrates. Their unique skull structure allows for stronger jaw muscles and greater flexibility, contributing to their ability to thrive in different ecological niches.