The Tyrannosaurid metatarsus: Bone strain and inferred ligament function

Abstract

Tyrannosaurid dinosaurs possess a metatarsus with an arctometatarsalian proximal constriction of metatarsal III, and strongly interlocking proximal articulations. Bone and inferred ligament morphologies are suggestive of modes of locomotor energy transmission. CT scanning and Finite Element Analysis (FEA) ofGorgosaurus libratus metatarsals test two hypotheses of tyrannosaurid arctometatarsus function: ligaments mediated transfer of energy from the central metatarsal to the outer elements, and ligaments arrested anterodorsal rotation of the distal portion of the central metatarsal. The results have implications for the use of FEA in functional morphology: 1) strain artifacts are identifiable under low-resolution modeling, but higher resolution is better; and 2) bone strain aids in testing hypotheses of ligament function. Concentrations of bone strain energy under postulated loading regimes forGorgosaurus support the hypothesis of axial energy transmission for the tyrannosaurid metatarsus, and indirectly support the rotation damping hypothesis. Palaeopathology provides a vital complement to engineering tests of these hypotheses.