Jonas Dagmire's Long Finger Metacarpal  

 

I think this is one of the parts from the Monkey Island quests. The quests as described on this site often fail to list the bones you get, because you are not offered any bones until you've done at least 3 of the 5 quests at each island (except Jardel's Hook), and you're not offered all three bones until you've done all 5 of the quests at each island. I don't remember whether this was the first, second, or third bone offered for doing the Monkey Island quests, but finish all five and it should be available. (If you ***** up and take plat instead of a bone, just repeat any of the repeatable quests at that island.)