3D topography as an indicator of change in food processing ability in elements of the conodont genus <i>Palmatolepis</i>

Conodont elements are components of the feeding apparatus of extinct early jawless vertebrates named conodonts. The shape of these tooth-like elements has been explored through different approaches to test whether their morphological changes through time were related to trophic ecology, environmental pressure or ontogeny. Several morphometric analyses have previously been performed on the 2D outline of P1 elements belonging to the conodont genus Palmatolepis from the Upper Devonian (381–360 Ma) of the Montagne Noire (France). These analyses showed a general decrease in breadth of P1 elements, which was interpreted as a long-term response to a change in available food resources and/or a possible change in the trophic position of this conodont. In contrast, analyses of calcium stable isotopes ratio have shown that no changes occurred in δ44/42Ca through time, suggesting that Palmatolepis did not change its trophic position despite the mentioned change in element morphology. To further investigate changes in Palmatolepis morphology through time, 3D topographic analyses were performed on Palmatolepis P1 elements spanning the Famennian. The results of this analysis highlight the first evidence of a sharpness increase over time in this genus. This covariation between the platform reduction and the increase in blade sharpness through time suggests morphofunctional changes allowing a more efficient processing of their prey. Moreover, allometric changes in Palmatolepis gracilis, the latest representative of the Palmatolepis genus, bring new insights into the palaeoecology of this species.