Keywords: reverse engineering, tetrapod skulls, medical image, reconstruction, finite element analysis, mesh processing.

Finite element analysis of living and extinct vertebrates to study biological structures exploring their function, morphological evolution, particularly adaptation and constraints has been conducted particularly in mammals and reptiles in the last ten years [1]. These studies probe how well-adapted is an organism for a particular function, although these predictions are not always plausible as the neontological work demonstrated that form does not always predict function, neither does function always predict form.

In this work we present a reverse engineering study using a geometrical reconstruction of an amphibian skull. For the first time, the chinese giant salamander (Andrias davidianus) is analysed using finite element software. The feeding behaviour is tested reproducing the in vivo conditions to understand the functional morphology of this amphibian. A reverse engineering procedure is used to understand biological structures exploring their function and morphological evolution.

Therefore, a medical image reconstruction is done from a real skull to create a three-dimensional solid model capable of analysis using the finite element software. This model has the boundary formed by curved surfaces obtained using interpolation methods and allows the finite element software to complete the final stage of the model development, i.e. the mesh processing, to generate the final mesh to be used in the analysis. Finally, the skull of the Chinese giant salamander (Andrias davidianus) is analysed using the finite element software ANSYS® 12.0 for Windows XP (32-bit system) to evaluate the stress state and the deformation of the different bites. We simulated feeding activity of the skull (and jaw) based on the muscle and bone distribution.

During the geometry reconstruction, a smooth and delete procedure must be done to avoid the rough geometry generated in the image segmentation because this roughness can generate many singularities in the geometry that will drive towards artificial noise in the stress results. As a consequence of this fairly idealized treatment of the geometry, an h-adaptive method with convergence of the mesh can be automatically done to obtain good stress results, without artificial noise related singularities.

This paper shows how to use reverse engineering to study the feeding behaviour of tetrapod skulls. But, the most important issue presented is the considerations taken into account during this procedure when the geometry is reconstructed from medical imaging and when the computational mesh is generated to solve the finite element problem.

1

E.J. Rayfield, "Finite Element Analysis and Understanding the Biomechanics and Evolution of Living and Fossil Organisms", Annual Review of Earth and Planetary Sciences, 35, 541-576, 2007. doi:10.1146/annurev.earth.35.031306.140104

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