The photo above shows the left dentary, still in the jacket. It has an oddly deformed area, indicated by the arrow.
If we look at the jacket from the side, it becomes apparent how this deformation occurred:
The arrow is indicating a second bone that has punched through the dentary. I believe this bone is the postorbital process of the frontal, a projection of the frontal bone the sticks down behind the eye socket. When the skull was crushed down onto the lower jaw, the postorbital process was pushed through the dentary.
Another interesting feature was revealed when the right dentary was removed. There was a thin layer of sediment, just a few millimeters thick, separating the dentary from the skull. This sediment contained several trace fossils, burrows formed by some type of invertebrate, like the one shown below: