Reptiles, the class Reptilia, are an evolutionary grade of animals, comprising today's turtles, crocodilians, snakes, lizards, and tuatara, as well as many extinct groups.

The earliest known reptiles originated around 315 million years ago during the Carboniferous period, having evolved from advanced reptile-like amphibians.

There are many diverse groups that are now extinct, in some cases due to mass extinction events.

The K–Pg extinction wiped out the pterosaurs, plesiosaurs, ornithischians, and sauropods, as well as many species of theropods (e.g. tyrannosaurs and dromaeosaurids), crocodyliforms, and squamates (e.g. mosasaurids).

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