So I had a horse die of starvation while I was still learning about the game. I couldn't figure out how to to butcher it, but did manage to get it to an outdoor refuse pile before it stunk up the place. Now there is a skeleton there, and I can't figure out how to retrieve it so that I can turn it into bone.
How do I turn a skeleton that is in an outdoor refuse pile into usable bone?
One of Dwarf Fortress' many quirks is that creatures who died of starvation are completely un-butcherable. It's a known bug.
Apparently, the only way Dwarves are satisfied eating 'Tame' animals, is if they've killed the animal with their own two hands via a butcher's shop (read: murder) either by manually toggling the animal for slaughter with v or via the animals subsection of the stocks screen (z).