Science and Technology Production
Congress
Authorship
Garderes, Juan P.
;
Toledo, N.
;
Whitlock, John A.
;
GALLINA, PABLO ARIEL
Date
2025
Publishing House and Editing Place
Asociación Paleontológica Argentina
Summary
Information provided by the agent in
SIGEVA
The arrangement and orientation of jaw muscles are fundamental to understand the biomechanics and feeding behavior in vertebrates. Based on these, the effective forces that the jaw musculature can apply to a lever system can be evaluated, considering mainly the mean orientation of the muscles regarding the orthal, sagittal, and coronal planes, which directly affect the bite forces an organism can exert. Among sauropod adductor muscles, diplodocoids exhibit palatal muscles that are oriented more...
The arrangement and orientation of jaw muscles are fundamental to understand the biomechanics and feeding behavior in vertebrates. Based on these, the effective forces that the jaw musculature can apply to a lever system can be evaluated, considering mainly the mean orientation of the muscles regarding the orthal, sagittal, and coronal planes, which directly affect the bite forces an organism can exert. Among sauropod adductor muscles, diplodocoids exhibit palatal muscles that are oriented more vertically than their temporal muscles, opposite to the arrangement in most dinosaur taxa. Bajadasaurus, a dicraeosaurid sauropod from the Lower Cretaceous of Neuquén, follows the diplodocoid pattern, showing an overall low-angled temporal and high-angled palatal muscular arrangement. This taxon would have produced low bite forces, similar to the theropod Erlikosaurus. For the latter, the maximum gape was estimated, showing that the maximum tensions its muscles can resist are reached at a gape of 43°. Using 2D ternary diagrams, here we analyze the variation in the mean orientation of the palatal muscles [muscles adductor mandibulae posterior (mAMP), pterygoideus ventralis (mPtv), and pterygoideus dorsalis (mPtd)] in Bajadasaurus, at different gape angles of 0°, 20°, and 45°, regarding the coronal, sagittal, and orthal planes. At 0°, mAMP shows the highest coronal angle (55°), while at the sagittal and orthal planes, mPtd shows the higher angles (64° and 26°, respectively). These positional values do not change at 20° and 45° gapes, but a notable increase is observed in the dorsoventral component of mAMP, almost equalling the mPtd angles (mean of 63°, among different gapes). Regarding the coronal angles, the most remarkable increases occur in the coronal components of mPtd at both open-gapes, increasing up to around 1000 % of the resting position. Conversely, the highest angular reduction is observed at the coronal component of mAMP, reducing by 23 % at 20° and by 45 % at 45°. Overall, the most variable palatal muscle in terms of orientation at different gapes is mPtd, while the most conservative –including the higher reductions regarding certain planes– is mAMP. The higher the angle of a muscle component relative to the orthal plane, the higher its mechanical advantage and its relevance in the orthal oral-processing movement. Following this, mAMP, based on its dorsoventral component increasing, is the palatal muscle that gains more relevance in the jaw-closing process at higher gape angles in Bajadasaurus, almost equalling the pterygoid muscles, which show relatively higher relevance at smaller gape angles.
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Key Words
SAUROPODABIOMECHANICSPALATAL MUSCULATUREJAWS