The Middle Ear of Coleonyx variegatus

In the gecko, Coleonyx variegatus, the tympanum is attached to the hyoid arch by a segment of the pharyngeal wall. Mechanisms which might allow the tympanum to operate if hyoid movements alter the tautness of the tympanum include the anchoring effect of the epihyal, the antagonistic action of the episternohyoideus muscles, and reduction of the hyoid movement by the holding effect of the cartilaginous connection of the epibranchials. Alternately, the tension of the tympanum may be maintained by distension of the pharyngeal wall during breathing or by increased rigidity of the columella brought about by pressure of the facial artery. There are apparently three routes by which ground vibrations may be transmitted to the inner ear from the lower jaw.