The feeding process of Balaenopteridae (rorquals) is characterized by an energetic event in which a large volume of seawater is engulfed and filtered. Here we identify a major structural component of a stay apparatus that exists in the rorqual craniomandibular system. This fibrous appendage of the temporalis muscle introduces a continuous, mechanical linkage between the supraorbital process of the frontal bone and the coronoid process of the mandible. It is named the frontomandibular stay. Anatomic relationships and biomechanical findings predict that this structure would control and assist a process of continuous change in position of the jaws during engulfment events. The dynamic form of mandibular kinesis produced would function to increase the power of feeding. Owing to the stay's nonmuscular construction, its mechanical action necessarily is driven by the kinetic mass of the moving whale.

Author notes

Associate Editor was Patricia W. Freeman.