Apparatus for detecting motions of a lower jaw relative to the upper jaw of a vertebrate, comprising a first holder (30) to be fixed to the head of a vertebrate with a fixed assignment relative to the upper jaw for accommodating transmitter or receiver units of a position determining system (1) for the detection of motion, a second holder (40A) to be fixed to the lower jaw on the left side for accommodating corresponding left-sided receiver and transmitter units of the position determining system, a third holder (40B) to be fixed to the lower jaw on the right side for accommodating corresponding right-sided receiver and transmitter units of the position determining system, and a first evaluation unit (13) for processing signals from the receiver units so as to generate a differentiated dynamic image of the motions of the left and right sides of the lower jaw from relative positional changes of the transmitter units (11) which are associated with the motions of the lower jaw and are detected by the receiver units.
