Decoupling geometry and topography reveals contrasting ecomorphological signals in carnivoran carnassial teeth

The lower carnassial tooth (m1) is a key innovation underlying the ecological diversification of Carnivora. However, their exceptionally diverse phenotypes result from both functional adaptation and phylogenetic inertia which challenges ecomorphological inferences. We investigate patterns of morphological convergence in the carnassial teeth of 142 extant carnivoran species spanning all terrestrial families and major dietary strategies. We compare the performance of occlusal topographic metrics (Relief Index, Dirichlet Normal Energy, and Orientation Patch Count rotated) and High-Density Three-Dimensional Geometric Morphometrics (HD3DGM) in distinguishing ecomorphological signal at high taxonomic level, a key element of large-scale diversity analyses.
Our results show that HD3DGM recovers a stronger and more consistent dietary signal than topographic metrics, particularly across dissimilar morphologies and at higher taxonomic levels. Within omnivory, insectivory, and frugivory, species sharing the same dietary strategies exhibit clear patterns consistent with morphological convergence in the geometric data while it is only true for frugivory when using topographic metrics. We show that many-to-one topography behaviour weakens the quality of ecomorphological inference at higher taxonomic scales. Our results reframe the context in which each method is most appropriately applied.