Adjective
keratinous (comparative more keratinous, superlative most keratinous)
Consisting of, or made from keratin.
Synonym: keratinaceous
As in the Giraffidae, skin covers the bony cores, but in the pronghorn it develops into a keratinous sheath which is shed and regrown on an annual basis. Source: Internet
Harmer, S. F. & Shipley, A. E. (1899) Close-up of the head of a southern cassowary All three species have a keratinous skin covered casque on their heads which grows with age. Source: Internet