How to get triangle indices for use with CalcBoneVertInfos?

The CalcBoneVertInfos is an extremely useful function for my needs:

IMeshUtilities::CalcBoneVertInfos(…);

For each bone in a skeletal mesh, it gives me an array of vertices (in bone local space) that are dominated by that bone. I can debug draw some point clouds and verify the vertices associated with each bone.

However I need the corresponding triangle indices as well. How can I get a corresponding list of indices that I can use to triangulate these vertices?