Strain estimation from distorted vertebrate fossils: application of the Wellman method

Abstract

Distortion of the vertebral column in fossils can be used for the estimation of two-dimensional finite strain by a simple geometrical technique, namely the Wellman method. We demonstrate application of the Wellman method to the distorted vertebral columns of a reptile and a stem-chordate, and use the results to restore the undistorted fossil shapes by a computer graphic method. The Wellman method is particularly efficient in situations where independent evidence for the principal strain directions, or undistorted forms, are lacking. The method is purely geometrical, easy to use, and rapid. It involves relatively low error, and works even when only a small segment of the distorted vertebral column is preserved.