What adaptation allowed reptiles to lay eggs that do not dry up in the sun?

Step-by-step solution

There are no specimens of these left with us. However, these were ancestors of modern day frogs and salamanders. The amphibians evolved into reptiles. They lay thick- shelled eggs which do not dry up in sun unlike those of amphibians . Again we only see their modern day descendents, the turtles, tortoises and crocodiles. Giant ferns (pteridophytes) were present but they all fell to form coal deposits slowly. Some of these land reptiles went back into water to evolve into fish like reptiles probably 200 mya (e.g. Ic