scleroderm

noun3

1. •
   A hardened or bony integument of various animals.
2. •
   (no longer used) One of a tribe of plectognath fishes (Sclerodermi) having the skin covered with hard scales, or plates, such as the cowfish and trunkfish.
3. •
   (no longer used) One of the Sclerodermata; a madrepore.