What material, also found in human fingernails, forms the outer covering (scutes) on the bony plates of the shell?

Answer

Keratin

The bony plates that make up the shell structure are covered externally by epidermal scutes composed of keratin, the same protein that constitutes human fingernails.

What material, also found in human fingernails, forms the outer covering (scutes) on the bony plates of the shell?
Shellreptileherbivoretortoiseslow