How did the first reptiles evolve on earth?

Answer 1

The first reptiles evolved from amphibians about 310-320 million years ago. It is known that amphibians live life in both water and land, but have to return to the water to lay their soft eggs.

As amphibians differentiated one group known as reptiliomorph labyrinthodonts became more accustomed to the dry land. They spent more time on land than in water. Eventually they adapted by growing hard, dry skin rather than the soft, wet skin of amphibians. They also adapted by laying hard shelled eggs on land rather than laying soft eggs in the water.

The first reptiles were largely overshadowed by the larger amphibians, which were more diverse and dominant prior to the Permian mass extinction. Hylonomus is the oldest-known reptile, and was about 8 to 12 inches (20 to 30 cm) long. Westlothiana has been suggested as the oldest reptile, but is for the moment considered to be more related to amphibians than amniotes.