Thanks Deb! I'd forgotten that I actually have the Fergus Henderson book that those recipes are based on. (it's upstairs and we've sold and not rebuilt our staircase, long story)
So the beef shank was basically a cut of meat with some bone in it, it wasn't quite what I needed for
marrow. What I had in Paris looked like this:

I was on a mission by this point though so we stopped by Kingsley's and they scrounged up a few
bones they said would work. Only one was more than an inch tall though. We roasted them at 450 in a cast iron skillet. The three small ones just melted away all the
marrow. The one little taller one kept maybe a tablespoon of
marrow. The taste was right but the texture wasn't as light and melty as it was before. It was also still a little pink but I thought if I cooked it any longer it would melt away too. But at least my husband was able to get a taste and see what I'd come from from France raving about.
Kathy Packard at Misty Meadows Farm is going to try to get me some leg
bones that will work. I'm still determined to have this amazing dish.
I don't imagine any restaurants in Louisville are doing
marrow, but if you hear, please let me know!