You can buy Arm ST for your jaw muscles instead of an arm. This increases the biting power of your jaws. This does not help with lifting (lifting with your mouth uses back and neck muscles) or throwing, but does increase the damage done by a bite and applies to contest of ST where someone you bit is trying to escape from your bite.
If you cannot use your mouth to do fine manipulation, buy this advantage with the -40% limitation for No Fine Manipulators. The limitation for large size also applies.