A WATER-TIGHT SKIN AND THE SHELLED EGG
From amphibians to reptiles
The reptiles evolved from an early ancestral group of amphibians (Subclass Labyrinthodontia) which have been extinct for 175 million years. Terrestrial Labyrinthodontia had strong limbs, robust bodies. The first animal with a dry skin was probably Seymouria which lived in the Permian (230 million years ago) is thought to be the link between the amphibians and the reptiles and was probably the first animal to have a hard-shelled egg that entirely freed its reproduction from water or extremely moist habitats. All amphibians require a moist environment to survive and reproduce, but the reptiles can occupy a dry environment due to their water-tight skin and the shelled eggs.