Development of a computerized system for three-dimensional shape reconstruction

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A computer-assisted system to virtually reconstruct original shapes of fossil specimens subjected to taphonomic deformation is developed. This system contains a newly designed algorithm to mathematically reverse non-homogeneous deformation of originally a symmetrical fossil, such as skull, based on its geometrical constraints.In a bisymmetrical bone, all anatomical landmarks on its mid-sagittal plane should be included in the same plane. In addition, each of bilateral pairs of landmarks should form a segment connecting the pair that intersects with the plane at right angle in its midpoint. However, if such a bilateral bone is deformed due to diagenesis during its fossilization, those geometrical constraints will no longer be maintained. In the present method, therefore, coordinates of all landmarks are firstly transferred so as to fulfill those geometrical conditions. Then, the entire shape of the fossil is transformed according to the movements of the landmarks for reversal of deformation, using a thin-plate spline function.The proposed methodology is applied for reconstructing the original shape of the deformed skull of Proconsul heseloni. In the present study, the volume of the fossil is extracted from the CT-scan images, and the surface is approximated by very tiny triangles to three-dimensionally represent its shape in a computer. Using the system, the reconstructed shape of the skull can be observed, manipulated, and measured. Moreover, a replica of the result can be created by stereolithography for evaluation of the reconstruction.Although the reconstruction is still incomplete due to inherent lack of information that can be extracted from the fossil for reversal of deformation, results indicate efficacy of the proposed computerized system for advanced morphometrical and biomechanical studies of fossil skulls.