Helmutstrebl’s ramus bone clearly grew in length. What caused it to do so?
Chewing + forward growth, the more forward grown you are the longer the ramus and more acute the gonial angle is usually
Here's an example, left skull has less forward growth and right has more, right skull has a better gonial angle. It seems like the posterior end of the jaws come down and forward and the anterior side comes up and forward, this might explain why the ramus gets longer and gonial angle improves.