All fishes secret a slimy protein. Amphibians have a thin stratum corneum. They produce a mucousy substance that slows dehydration. Mucus glands keep the skin moist and allow skin breathing. Granular glands secrete toxins - This is why dogs spit out toads.
Reptiles use keratin to waterproof.
In snakes and lizards the old epidermis is shed periodically. The epidermis divides and a new inner epidermal layer forms. The 2 epidermal layers separate and the outer one is lost as a whole piece or in patches. Turtles and crocs have scale-like plates called scutes. The scales of snakes and lizards are also referred to as scutes.