Fig. 2 in The origin of ammonoid locomotion

Fig. 2. Phylogenetic change in orientation of the conchs and swimming velocity of Bactritida and primitive Ammonoidea. Outlines of the conchs of one bactritid and nine ammonoids from the Early and Middle Devonian with body chamber lengths (BCL), orientation of the aperture (OA), and relative swimming speed. Centre of gravity is indicated by a cross and the centre of buoyancy by a circle (for further explanations see Fig. 1).