Final answer:
Reptiles are amniotes with terrestrially adapted eggs and tetrapods descended from four-limbed ancestors. They are gnathostomes, meaning they have jaws, and are vertebrates with bony skeletal structures. These characteristics define their adaptability for terrestrial living and evolutionary relationships with other animal groups.
Step-by-step explanation:
Reptiles are amniote, tetrapod, osteichthyan, gnathostome, vertebrate, chordate, deuterostome, bilaterian animals. This description encompasses several classifications that describe their evolutionary history, physical characteristics, and their development.
Amniote means that reptiles produce eggs with specialized membranes, namely the yolk sac, amnion, chorion, and allantois, that allow them to lay eggs on land, constituting a significant adaption from aquatic environments.
Tetrapods are animals with four limbs, and reptiles are classified as such even in the absence of limbs, like snakes, because they are descended from four-limbed ancestors. Gnathostomes are jawed vertebrates, which includes reptiles along with other animals such as fishes and mammals. As osteichthyans, they belong to a group that includes all bony fishes and terrestrial vertebrates that evolved from them.
eptiles are also characterized by their scaly skin and their ability to reproduce sexually often laying shelled eggs on land. They are distinguished from amphibians by their terrestrially adapted eggs and various physical and reproductive adaptations that enable life out of water.