Fig. 14 in New teeth of allotherian mammals from the English Bathonian, including the earliest multituberculates

Fig. 14. Diagrams to illustrate postulated evolution of occlusion. A–E. Divergence between Allotheria and Mammaliaformes. The teeth are seen mesiodistally, buccal to the left. Arrows indicate direction of the power stroke. A. Plesiomorphic condition, e.g., Sinoconodon, with no occlusal contact. B, C. Opposition develops by formation of supplementary cusprows in Allotheria; B is a hypothetical transitional stage. D. Unilateral transverse shearing in morganucodonts. E. Rearrangement (triangulation) of cusps, as in symmetrodonts, resulting in mesially and distally facing wear facets. F–I. Allotherians illustrating stages in the evolution of palinal occlusion. Teeth seen in side view, distal to the left. F. Vertical crushing in Theroteinus. G. Distally oblique crushing in Millsodon. H. Basin grinding with palinal movement in Thomasia. I. Horizontal palinal grinding in multituberculates.