Where did the “Keep Additional Bones” check-box go when importing a Humanoid character into Mecanim?
Changes:
Mecanim: Remove Keep Additional Bones for Humanoid Rig at import. Use Skeleton mask instead.
For every animation, that you have now on your character, you can apply Mask and decide which bones shoud be moving and which not.
Go to the Animations tab (In the import settings of your character), select some of the animations and go way down. You will see a “Mask”. Click the arrow to open it. Create new Avatar mask and include all of your joints, then apply that mask to all animations, that you have on your character…