 To prevent loss of moisture reptilian skin lost the softness and moisture of amphibian skin and developing a thick "stratum corneum" with multiple layers of lipids which served as an impermeable barrier as well as provided protection from the ultraviolet.Over time, reptilian skin cells became highly keratinised, horny, sturdy and desiccated.The surfaces of the dermis and epidermis of all reptilian scales form a single contiguous sheet, as can be seen when the snake sheds its skin as a whole.