There is no general model for occlusal kinematics in conodonts

Knowledge of conodont element function is based largely on analysis of morphologically similar P-1 elements of few comparatively closely related species known from abundant articulated remains. From these, a stereotypical pattern of rotational occlusion has been inferred, leading to the suggestion that this may represent a general model for ozarkodinin P-1 elements at the very least. We test the generality of this occlusal model through functional analysis of Pseudofurnishius murcianus P-1 elements which, though superficially similar to homologous elements in gnathodids, evolved their platform morphology independently, through a different mode of morphogenesis, and in a different topological position within the element. Our integrated functional analysis of several articulated clusters of P-1 elements encompassed physical and virtual occlusal analyses, constrained by microwear and sharpness analyses. All of the evidence supports an occlusal model in which the Pseudofurnishius P-1 elements occluded with the dextral blade located between the rostral face of the sinistral blade and the first cusp of the rostral primary process. In achieving this, the dorsal and ventral blades guided the opposing elements, and the rostral processes of both elements guided the final stages of precise occlusion. Spalling and microwear on the non-occlusal side of the element evidence malocclusion, requiring the complete separation of elements within the occlusal cycle. This occlusal cycle is entirely linear, orthogonal to the plane of attachment of the elements. Evidently, the rotational occlusal model is not general for P-1 elements, even for ozarkodinins, and it is likely that among conodonts occlusal kinematics are as disparate as element morphologies. Attempts to elucidate the diversity of occlusal kinematics and, therefore, feeding ecologies of conodonts will be repaid by an understanding of the role of this important abundant and diverse clade in Palaeozoic and Mesozoic marine ecosystems.