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THE UNIVERSITY OF CALGARY Eric Snively A ... - Ohio University

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CHAPTER 4: Finite element model of locomotor stress in the metatarsus of<br />

INTRODUCTION<br />

Gorgosaurus Iibfatus (Tyrannosauridae)<br />

The third metatarsal (MT III) of tyrannosaurids is triangular in distal cross<br />

section. The tensile keystone hypothesis (Chapter 3) proposes that under high<br />

impulse Ioadings, with the metatarsus acutely angled to the substrate, the distal<br />

portion of MT III is displaœd anterodorsally. Ligaments arrest this displacement,<br />

and draw metatarsals II and IV towards the planta centerline of MT Ill. These<br />

loadings therefore unify the structure distally. The metatarsals are less subject<br />

individually to torsion and shear, and their collective strength is thereby<br />

increased.<br />

A prerequisite to the tensile keystone hypothesis is the structural integnty of<br />

the proximal splint of MT III. Using beam theory equations, Holtz (1 994a) found<br />

that the splint could not support body weight in large tyrannosaurids, but did not<br />

investigate the combined effects of locomotory stresses on the splint and the rest<br />

of the metatarsus, This chapter incorporates morphology, biological material<br />

properties, and loading environments of the metatarsals into a finite element<br />

stress analysis. Finite element analysis (FEA) elucidates stress and strain within<br />

constitutive bones of the arctometatarsus, and reveals the potential role of<br />

ligaments on intemietatarsal kinematics.<br />

Finite element modeling: background and applicabil@f to biological questions<br />

Finite element analysis determines stresses and strains within a structure by<br />

subdividing it into a finite number of shapes (elements) connected at points

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