What are the scales on all snakes and most lizards are made of?

Keratin is the tough, fibrous protein that forms the outer layer of reptile scales, so the scales on all snakes and most lizards are made of keratin. These scales are keratinized parts of the epidermis, creating a protective, water-resistant armor. That’s why reptiles can thrive in dry, abrasive environments. Context tip: It’s the same protein that makes your hair and nails, bird feathers, and mammal hooves. By contrast, fish scales are mostly bony, not keratin. Ecdysis is the process of shedding old skin and scales, not the material itself, and ankyloglossia is a tongue condition in humans. Memory hook: “Keratin = ‘ker-armor’”—the hard coating reptiles wear.