- 300 From amphibians came the first reptiles. Hylonomus is the earliest known reptile. It was 20 cm long (including the tail) and looked similar to modern lizards, had small sharp teeth and probably ate millipedes and early insects. It is a precursor of later amniotes and mammal-like reptiles.
- Evolution of the amniotic egg gives rise to the Amniota, reptiles who can reproduce on land and lay eggs on dry land. They did not need to return to water for reproduction. This adaptation gave them the capability to colonize the uplands for the first time.
Reptiles have advanced nervous system, compared to amphibians. They have twelve pairs of cranial nerves.