I did a bit more reading, and according to messybeast.com, a lot of these two-face mutations are caused by a problem with an enzyme called the sonic hedgehog enzyme. Anybody else know anything about this?
The right face had the right half of the soft palate, and the left face had the left half of the soft palate, but it has two tongues, which fit into the cavity where the soft palate should be. I also took x-rays, but haven't got those scanned yet.