Bone Devil's Sting and Improved Natural Attack.

[bigrig107]

So, the bone devil's sting is a primary natural attack that does 3d4 damage.

Looking at the natural weapons table tells us that a Large sting should do 1d6.

What happens if a bone devil takes Improved Natural Attack (sting)?
What's the damage dice then?

[UnArcaneElection]

Not sure, but if you can find something that says what to do with non-standard natural attack dice more generally, it probably has your answer. Such a thing exists for manufactured weapons, but not sure about natural attacks.

Edit: Naively looking in the feat itself (Improved Natural Attack) and at the Natural Attacks by Size table (probably the same one you found, in here -- scroll down to Natural Attacks by Size), I would expect that since 1d4 goes to 1d6 with a size increase of 1 step or with Improved Natural Attack, 3d4 would go to 3d6.

[James Risner]

If 3d4 goes to 3d6 (I didn't verify from the FAQ), then it would be 3d6.

Specifically, what ever it is using would increase unless it has something already increasing its die size. (Also didn't check)

[dragonhunterq]

FAQconfirms 3d6 (3d4=2d6, +2 steps)

[bigrig107]

Oh, cool! I didn't know that FAQ existed.

[Nefreet]

It took a lot of work to achieve.