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Smilodon fatalis jaw function

Ben Creisler

A new paper in PLoS ONE that may be of interest:

Jeffrey G. Brown (2014)
Jaw Function in Smilodon fatalis: A Reevaluation of the Canine
Shear-Bite and a Proposal for a New Forelimb-Powered Class 1 Lever
PLoS ONE 9(10): e107456.

The jaw function of Smilodon fatalis has long been a source of debate.
Although modern-day lions subdue large prey through the use of a
suffocating throat bite, the dramatically elongated maxillary canines
of S. fatalis suggest an alternative bite mechanism. The current
literature favors a “canine shear-bite,” in which the depression of
the cranium by the ventral neck flexors assists the mandibular
adductors in closing the jaws. Although the model makes intuitive
sense and appears to be supported by scientific data, the mechanical
feasibility of "neck-powered" biting has not been experimentally
demonstrated. In the present study, the computer-assisted manipulation
of digitized images of a high-quality replica of an S. fatalis neck
and skull shows that a rotation of the cranium by the ventral neck
flexors will not result in jaw closure. Instead, the cranium and
mandible rotate ventrally together (at the atlantooccipital joint),
and the jaws remain in an open configuration. The only manner by which
rotation of the cranium can simultaneously result in jaw closure is by
an anterior rotation at the temporomandibular joint. Based on this
finding, the author proposes a new Class 1 lever mechanism for S.
fatalis jaw function. In this model, the mandible is immobilized
against the neck of the prey and a dorsally directed force from the
extension of the forelimbs rotates the cranium anteriorly at the
temporomandibular joint. The maxillary canines pierce the prey’s neck
and assist in clamping the ventral neck structures. The model is based
on a maximum gape angle of approximately 90° and incorporates a
secondary virtual point of rotation located slightly anteroventral to
the temporomandibular joint. The Class 1 Lever Model is mechanically
feasible, consistent with current data on S. fatalis anatomy and
ecology, and may provide a basis for similar studies on other fossil


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