A similar fundraising technique is used with boats. For
construction or restoration you "sell" a plank on the
Boat. Limited items like masts, ships wheel, bowsprit were
higher dollar items. Years later I have met people who
refer to being a "plank owner on the schooner
whatshername" leading me to think you should sell a plank
(or bone) once. You may want to establish the mimimum
donation fairly high.

 Make the "bone owner (?)" a special list of donors who
are likely contribute to the upkeep of their Mammoth.
Having a high quality line drawing or model of the beast
or boat is a very classy tool.

I have seen the same idea used for outdoor parks, where
they sell a brick in the walkway.

How many bones does a Mammoth have?