Imagine a clam shape with a mouth. Looking at it from front on with mouth open it would look a bit similar to two semi circles sitting together with the top semi circle moving up and down in the Y axis and the pivot point at the rear on the Z axis. Now, if the clam was turned sideways the Z axis would be at the far side and the top semi circle would move similar to a clapper board with one end up on an angle and the pivot end remaining still.

So the question is, how would you set up a shape like this using bones and smart bone actions? I tried using layers an no bones and animating the pivot point in smartbone mode but pivot points are not an animate able feature.
Here's the tricky part, I want to attach a set of eyeballs to the front of the clam shape as well.
Can anyone suggest a simple way to do this?
Any ideas?
Thanks
D.K