Fig. 4 in The origin of ammonoid locomotion

Fig. 4. Transformations in conch morphology of eight primitive ammonoids from the Early and Middle Devonian (from bottom to top: Kokenia, Metabactrites, Anetoceras, Erbenoceras, Chebbites, Talenticeras, Mimagoniatites, Agoniatites). Subdivision of the coiling modes is slightly arbitrary, especially the differentiation between the crioconic and the cyrtoconic state. In that case, it was the intention to clarify the changes in coiling and not to quantify the curvature. Consequently, this imprecision appeared justifiable. In the left column, the body chamber length (BCL) is given at the top right, the angle of the orientation of the aperture (OA) at the bottom left and a code for the coiling mode (ontogeny) at the bottom right. The second column displays the complete conchs with the colour code for the coiling modes (white—cyrtoconic, subtle curvature; light grey—crioconic, distinctly curved, but whorls not in contact; medium grey—advolute, whorls close or touching; dark grey—evolute, whorls slightly overlapping). Columns three to six show the isolated conch parts sorted according to the coiling mode.