by Professor W. S. Bullough.

The early amphibians had to return to water to lay their eggs, but the reptiles that followed them were less dependent on water since their shelled eggs could be laid on dry land. Reptiles became adapted to very many different ways of life-many were especially suited for life in desert conditions, some returned to the water, and others developed wing membranes and became the first vertebrates to conquer the air.
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