How do I get a Monster Keenbone and Rath Marrow?

To upgrade to a Vortex Hammer +, I need the following:

Three Lagia Horns (easy enough - I've become great at farming Lagia)

and

Two Monster Keenbones (never found one - exactly what do I slay, and in which quest(s) would it appear?)

also, to upgrade to a Red Bludgeon, I need:

One Rath Marrow (do I farm Rathian or Rathalos, and do I need to break something specific, or do I need to over-farm and go for broke against the Desire Sensor?)

I just got the Rath Marrow I need. I'll post specifics on the Hunting Journal.

Keenbones are high rank only. I'm assuming you're still in 5* quests, which are just before high rank.

Something to keep in mind the next time you're missing some sort of monster bone; they're extremely easy to come by in quest rewards, and you'll usually find one in the first hunt they're available. If you don't have a single a Keenbone, Finebone, Slogbone or whatever, you simply aren't far enough in the game to obtain them yet.

I believe I only need to hunt Barioth and Diablos and then I will be at high rank.