Bones are often the focus of taxidermy. You can't do much with bones; they are what's left after the fur, skin, organs, and meat have been removed.

The earliest known mount in existence today is a crocodile hanging from the ceiling of a cathedral in Ponte Nossa, Italy. A document from 1534 references it specifically, so we know it's at least that old.

Depending on how it preserved it can stay intact and presentable for decades. That is if you care for it properly; keep it dry and out of the sun, prevent insect infestations and such.