Collision primitives - Oriented Circle

I was wondering if it is possible to implement a simple oriented 2D bounding circle as a collision primitive in OgreNewt. It is the simplest collision check against a radius and I think it is useful even in 3D. (e.g. say you want to check proximity to an object on the ground). I've looked through the Collision Primitives supported by Newton and it isn't implemented. I guess Ellipsoid is the closest to that but it is overkill in some cases

If you want a sphere (aka a 3D circle), just make an ellipsoid with the same radius in each direction. it is the most efficient primitive.

no, I was actually referring to a pure 2D circle whose plane will be oriented towards a given vector so that the collision check is only done against an oriented radius