“Acoustic window” in the mandibular of dolphins: evaluation of the bone thickness

The mandibular sound conduction hypothesis suggests that dolphins have functionally replaced the external pinna with an “acoustic window” in the low jaw. Using industrial tomography, the lower jaws 3D models of the odontocetes six species were built. In the obtained models, the analysis of the bone thickness in the area of the supposed “acoustic window” showed a dependence of the bone wall thickness on the size of the animal. The area of the greatest thinning of the lateral wall of the lower jaw in the studied samples was determined mainly in the upper angle of the proximal part of the lower jaw or near the lower angle of the lower jaw, and not in the center, as previously assumed.