Final answer:
The two groups of diapsid reptiles are the Lepidosauromorpha and Archosauromorpha, which include modern lizards, snakes, tuataras, crocodiles, alligators, and the extinct dinosaurs and birds, with birds having evolved from theropod dinosaurs.
Step-by-step explanation:
The two groups of diapsid reptiles are the Lepidosauromorpha and Archosauromorpha.
The lepidosaurs include modern lizards, snakes, and tuataras. In contrast, the archosaurs encompass modern crocodiles, alligators, and extinct species such as ichthyosaurs, pterosaurs, dinosaurs, and birds. It is essential to understand that birds evolved from a branch of maniraptoran theropod dinosaurs, affirming their classification as part of the Archosauromorpha.
This evolutionary lineage reveals fascinating connections such as the similarity of hip and wrist bone structures and the presence of a wishbone, which is observed in both these theropods and modern birds. These details provide a deeper insight into the rich diversity and complex evolutionary history of diapsid reptiles.