Have you seen a lizard’s egg? It has a white shell. Reptile eggs have a shell, while amphibian eggs do not have one. The shell prevents the egg from drying up. In fact, the development of such an egg was the key to the evolution of reptiles. Unlike amphibian eggs, such eggs could be laid on land. Amphibians were the ancestors of reptiles. Some scientists believed that the amphibian ancestors spent a lot of time on the land, and the development of the egg with a shell followed. Other scientists like Alfred S. Romer believe that the earliest reptiles came ashore mainly to lay eggs, just as turtles and sea snakes do today.
The Mesozoic Era, the age between 63 and 245 million years ago, was the golden age of the reptiles. The ancestors of all later day reptiles called stem reptiles or cotylosaurs dominated the Earth. They were lizard like, and hopped like frogs. Turtles may have arisen directly from stem reptiles. Turtles are regarded as the oldest among modern day reptiles.