In life, SUE the T. rex's claws were covered in a sheath of keratin- the same material that your fingernails are made of. This outer layer was constantly growing and wearing down as SUE walked around. After SUE died, only the bony core of the claw became fossilized. This cast is one of those cores. Proudly display your love for dinosaurs and paleontology on your mantel, desk, or shelf with this hand-cast replica.