Brachiopods have a lateral outline which is quite important in systematic studies. It is often assessed by a qualitative evaluation and linear measurements, which are not clear enough and precise for describing the shape of the shell and its changes. In this work we shed light on a new approach based on digital image processing of these species. Our approach includes two steps. The first is to determine the contour of the species from their 2D images using the implicit active contours (Level set). The second step is to use the CSS (Curvature Scale Spaces) to index curves. This new mathematical model reported here presents a suitable morphologic descriptor which allows us to: (1) express a rigorous morphologic quantitative assessment; (2) emphasize the various differences between different shapes.