Published as part of Ubukata, Takao, Tanabe, Kazushige, Shigeta, Yasunari, Maeda, Haruyoshi & Mapes, Royal H., 2008, Piggyback whorls: A new theoretical morphologic model reveals constructional linkages among morphological characters in ammonoids, pp. 113-128 in Acta Palaeontologica Polonica 53 (1) on page 116, DOI: 10.4202/app.2008.0108, http://zenodo.org/record/13274627

Fig. 4. Schematic diagram of an ammonoid whorl section. The shape of the whorl (S) is represented by the closed curve illustrated here which is given by the parametric equations indicated above the diagram. Figures in the right show examples of hypothetical whorl shapes with systematically varying the S value.