Informal name for non-mammal-like lineages of amniotes.

Among amniotes, the reptiles include especially , , , , and . These extant tetrapods generally are all ecotothermic.

More generally, the amniotes include the diapsids and other reptiles in combination with the synapsid mammals. Ambiguously, as more broadly defined, the reptiles also can be viewed as being equivalent to the amniotes.

In addition, even if more narrowly defined, the reptiles as a clade should include the birds.

Thus,

     amphibians → amniotes ≈ reptiles → diapsids (etc.) → → birds.

Similarly,

     amphibians → amniotes → synapsids ≈ → mammals.

For additional discussion, see class Reptilia.