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Bone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the late Eocene of Egypt estimated by finite element analysis.

Snively E, Fahlke JM, Welsh RC - PLoS ONE (2015)

Bottom Line: The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion.Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs.Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Wisconsin-La Crosse, 1725 State Street, La Crosse, Wisconsin, United States of America.

ABSTRACT
Bite marks suggest that the late Eocence archaeocete whale Basilosaurus isis (Birket Qarun Formation, Egypt) fed upon juveniles of the contemporary basilosaurid Dorudon atrox. Finite element analysis (FEA) of a nearly complete adult cranium of B. isis enables estimates of its bite force and tests the animal's capabilities for crushing bone. Two loadcases reflect different biting scenarios: 1) an intitial closing phase, with all adductors active and a full condylar reaction force; and 2) a shearing phase, with the posterior temporalis active and minimized condylar force. The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion. Reaction forces with all muscles active indicate that B. isis maintained relatively greater bite force anteriorly than seen in large crocodilians, and exerted a maximum bite force of at least 16,400 N at its upper P3. Under the shearing scenario with minimized condylar forces, tooth reaction forces could exceed 20,000 N despite lower magnitudes of muscle force. These bite forces at the teeth are consistent with bone indentations on Dorudon crania, reatract-and-shear hypotheses of Basilosaurus bite function, and seizure of prey by anterior teeth as proposed for other archaeocetes. The whale's bite forces match those estimated for pliosaurus when skull lengths are equalized, suggesting similar tradeoffs of bite function and hydrodynamics. Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs. However, comparison of force estimates from FEA and regression data indicate that B. isis exerted the largest bite forces yet estimated for any mammal, and greater force than expected from its skull width. Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation.

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Exploratory plate-model distribution of von Mises stresses.Von Mises stresses (σvM; maximum shown here of 20 MPa) in Basilosaurus isis biting on its upper third premolar, assuming muscle specific tension of 37 N/cm2. Oblique view. Note an arc of evident stress in the maxilla dorsal to the bite point, and muscle-induced stresses from the force of m. temporalis.
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pone.0118380.g003: Exploratory plate-model distribution of von Mises stresses.Von Mises stresses (σvM; maximum shown here of 20 MPa) in Basilosaurus isis biting on its upper third premolar, assuming muscle specific tension of 37 N/cm2. Oblique view. Note an arc of evident stress in the maxilla dorsal to the bite point, and muscle-induced stresses from the force of m. temporalis.

Mentions: Under the load case with full muscle activation and constraints at P3 and both jaw joints, all reaction forces scaled linearly with specific tension. With the realistic ST of 37 N/cm2 [29], the average theoretical food reaction force at P3 was 16,461 N (Table 3). The joint reaction force was greater on the right side at 12,523 N, versus 9,298 N on the left, despite greater muscle force and a bite point both on the left side (Table 3). Reaction forces were insensitive to element thickness or type and hence to von Mises stress (Fig. 2), with a magnitude at P3 of 16,483 N for elements of 2 cm thickness, only 0.18% greater than 16,453 N for 0.5 cm thickness (Fig. 2). Vertical (z-axis) bite reaction force was more variable, with relative forces reversed at 1.28% greater for the model at 0.5 cm thickness than at 2 cm. Stress magnitudes (Fig. 2) do not affect hypothetical distributions of stress (Fig. 3) in tests with models of different plate thickness.


Bone-breaking bite force of Basilosaurus isis (Mammalia, Cetacea) from the late Eocene of Egypt estimated by finite element analysis.

Snively E, Fahlke JM, Welsh RC - PLoS ONE (2015)

Exploratory plate-model distribution of von Mises stresses.Von Mises stresses (σvM; maximum shown here of 20 MPa) in Basilosaurus isis biting on its upper third premolar, assuming muscle specific tension of 37 N/cm2. Oblique view. Note an arc of evident stress in the maxilla dorsal to the bite point, and muscle-induced stresses from the force of m. temporalis.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4340796&req=5

pone.0118380.g003: Exploratory plate-model distribution of von Mises stresses.Von Mises stresses (σvM; maximum shown here of 20 MPa) in Basilosaurus isis biting on its upper third premolar, assuming muscle specific tension of 37 N/cm2. Oblique view. Note an arc of evident stress in the maxilla dorsal to the bite point, and muscle-induced stresses from the force of m. temporalis.
Mentions: Under the load case with full muscle activation and constraints at P3 and both jaw joints, all reaction forces scaled linearly with specific tension. With the realistic ST of 37 N/cm2 [29], the average theoretical food reaction force at P3 was 16,461 N (Table 3). The joint reaction force was greater on the right side at 12,523 N, versus 9,298 N on the left, despite greater muscle force and a bite point both on the left side (Table 3). Reaction forces were insensitive to element thickness or type and hence to von Mises stress (Fig. 2), with a magnitude at P3 of 16,483 N for elements of 2 cm thickness, only 0.18% greater than 16,453 N for 0.5 cm thickness (Fig. 2). Vertical (z-axis) bite reaction force was more variable, with relative forces reversed at 1.28% greater for the model at 0.5 cm thickness than at 2 cm. Stress magnitudes (Fig. 2) do not affect hypothetical distributions of stress (Fig. 3) in tests with models of different plate thickness.

Bottom Line: The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion.Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs.Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Wisconsin-La Crosse, 1725 State Street, La Crosse, Wisconsin, United States of America.

ABSTRACT
Bite marks suggest that the late Eocence archaeocete whale Basilosaurus isis (Birket Qarun Formation, Egypt) fed upon juveniles of the contemporary basilosaurid Dorudon atrox. Finite element analysis (FEA) of a nearly complete adult cranium of B. isis enables estimates of its bite force and tests the animal's capabilities for crushing bone. Two loadcases reflect different biting scenarios: 1) an intitial closing phase, with all adductors active and a full condylar reaction force; and 2) a shearing phase, with the posterior temporalis active and minimized condylar force. The latter is considered probable when the jaws were nearly closed because the preserved jaws do not articulate as the molariform teeth come into occulusion. Reaction forces with all muscles active indicate that B. isis maintained relatively greater bite force anteriorly than seen in large crocodilians, and exerted a maximum bite force of at least 16,400 N at its upper P3. Under the shearing scenario with minimized condylar forces, tooth reaction forces could exceed 20,000 N despite lower magnitudes of muscle force. These bite forces at the teeth are consistent with bone indentations on Dorudon crania, reatract-and-shear hypotheses of Basilosaurus bite function, and seizure of prey by anterior teeth as proposed for other archaeocetes. The whale's bite forces match those estimated for pliosaurus when skull lengths are equalized, suggesting similar tradeoffs of bite function and hydrodynamics. Reaction forces in B. isis were lower than maxima estimated for large crocodylians and carnivorous dinosaurs. However, comparison of force estimates from FEA and regression data indicate that B. isis exerted the largest bite forces yet estimated for any mammal, and greater force than expected from its skull width. Cephalic feeding biomechanics of Basilosaurus isis are thus consistent with habitual predation.

Show MeSH
Related in: MedlinePlus