Cranial design and function in a large theropod dinosaur

Abstract

Finite element analysis (FEA) is used by industrial designers and biomechanicists to estimate the performance of engineered structures or human skeletal and soft tissues subjected to varying regimes of stress and strain. FEA is rarely applied to problems of biomechanical design in animals, despite its potential to inform structure-function analysis. Non-invasive techniques such as computed tomography scans can be used to generate accurate three-dimensional images of structures, such as skulls, which can form the basis of an accurate finite element model. Here we have applied this technique to the long skull of the large carnivorous theropod dinosaur Allosaurus fragilis. We have generated the most geometrically complete and complex FEA model of the skull of any extinct or extant organism and used this to test its mechanical properties and examine, in a quantitative way, long-held hypotheses concerning overall shape and function. The combination of a weak muscle-driven bite force, a very 'light' and 'open' skull architecture and unusually high cranial strength, suggests a very specific feeding behaviour for this animal. These results demonstrate simply the inherent potential of FEA for testing mechanical behaviour in fossils in ways that, until now, have been impossible.

Bone strain gradients and optimization in vertebrate skulls

“…In vivo bone strain gradients, albeit less well documented, have also been reported in the skull of the baboon Papio (Hylander et al 1991), the sheep Ovis , and the hyrax (Lieberman et al 2004);Buckland-Wright (1978) reports in vitro strain gradients in dry cat skulls during loading and in anaesthetized cats during muscle stimulation. Together, these data suggest that bone strain gradients are pervasive in tetrapod skulls and cannot be invoked as evidence for specific feeding behaviors (e. g., Rayfield et al 2001).…”

Using finite‐element analysis to investigate suture morphology: A case study using large carnivorous dinosaurs

“…Although the constructional parameters, assumptions, loading conditions, and specimen chosen for the model have been detailed elsewhere (Rayfield, 2001;Rayfield et al, 2001), they are briefly repeated here for continuity and clarity. MOR 693, a large articulated Allosaurus skull with mandibles, was subjected to computed tomography (CT) scanning at the Deaconess Hospital, Bozeman, Montana.…”

“…On meshing, 146,398 four-noded solid tetrahedral elements were produced, comprising 38,344 nodes with 107,421 degrees of freedom. Elements were ascribed the material properties of bovine Haversian bone on the basis of similar histological structure in theropod and bovine bone after Rayfield et al (2001): Young's modulus, 10 GPa; shear modulus, 3.6 GPa; Poisson ratio, 0.4; density, 1.895 kg/m 2 (Reilly and Burstein, 1975). Properties of bovine dentine were applied to the teeth: Young's modulus, 21 GPa; shear modulus, 8 GPa; Poisson ratio, 0.31; density, 2.076 kg/m 2 (Waters, 1980).…”

Finite element analysis in vertebrate biomechanics

“…However, there are also many animals for which living analogs are either not obvious or are not available for study; FEA provides a method to study structure-function relationships in these animals. Good examples of applications of FEA to fossils include studies of pterosaurs (Fastnacht et al, 2002), synapsids (Jenkins et al, 2002), dinosaurs (Rayfield et al, 2001;Snively and Russel, 2002;Rayfield, 2004), and vertebrate skulls in general (Preuschoft and Witzel, 2002). …”

“…Rayfield's studies of dinosaur skulls exemplify the strengths and problems surrounding FEA of fossil taxa (Rayfield et al, 2001;Rayfield, 2004). In her contribution to this issue, Rayfield (2005) addresses a thorny but extremely important question: the functional significance of sutural morphology in skulls.…”