A new study on the lower dentition of carnivorans (dogs, cats, bears and relatives) helps clarify which aspects of their ecology and evolutionary history are captured by different methods of dental shape analysis.
An international team led by scientists from University of Liège examined in detail the ecological and evolutionary signals preserved in the first lower molars of carnivorans. By comparing several analytical methods, the researchers assessed which approach performs best at detecting ecological aspects of tooth shape. Published in Proceedings of the Royal Society B, the study provides new insights into the complex interplay between dietary adaptations and traits inherited through evolutionary history.
Teeth form the first point of contact between an animal and its food, making them particularly valuable to evolutionary biologists and palaeontologists. In carnivorans, the first lower molar is especially important. It is also known as the lower carnassial, a very specialized tooth that initially appeared to slice through meat efficiently but now evolved a myriad of different shape in extant species with various diets (Figure 1).
Figure 1: Evolutionary tree of extant carnivorans showing a subset of species exhibiting various diets, highlighting the different dental adaptations observed for different diets across various families.
“The carnassial tooth is a key innovation that underlies the ecological diversification of Carnivora” explains Melvin Vankelst, PhD student at the University of Liège and Royal Belgian Institute of Natural Sciences; “Carnivoran lower molars display an extraordinary diversity of shapes, arguably among the greatest found in any mammalian tooth. They are also thought to preserve a stronger dietary signal than upper teeth, making them an ideal study system for this project.
Researchers can quantify three-dimensional dental shape using two main approaches. The first, dental topography, analyses the chewing surface and summarizes different features such as the surface complexity and the orientation of cusps faces. The second, three-dimensional geometric morphometrics describes the overall shape of the tooth crown using a dense set of three-dimensional points placed across each specimen. Until now, however, the relative strength of the dietary and evolutionary signals captured by these methods remained unclear (Figure 2).
Figure 2 : Figure summarizing the data acquisition for each method.
In this paper, the researchers refined the geometric morphometric protocol to improve its precision and better tailor it to the study of these teeth. The result is a High-Density Three-Dimensional Geometric Morphometric protocol, or HD3DGM for short, that offers remarkable analytical power. The study revealed a clear pattern: HD3DGM was generally better at detecting the subtle ecological and phylogenetic signals preserved in the teeth of living carnivorans, particularly when comparing broader taxonomic groups. “The morphometric approach generates a much larger amount of shape data, which helps recovering subtle ecomorphological patterns,” explains Prof. Valentin Fischer, head of the Evolution and Diversity Dynamics lab, “topographic methods, by contrast, usually produce a single value per species, which may obscure subtle changes”. This limitation may be especially important in large datasets, where pronounced differences in tooth shape among families can blur the patterns detected through topographic analyses (Figure 3).
Figure 3: Landscape showing the variation in topographic metrics across the shape space but also illustrating that some very different teeth can bear similar topographic values.
The study also revealed that different dietary adaptations are associated with different degrees of evolutionary convergence. Most dietary strategies occupy relatively restricted regions of tooth-shape space. Hypercarnivory, an extreme specialization for eating meat, stands out because it is associated with two main recurring tooth morphologies. “These distinct architectures may represent alternative functional solutions shaped by the evolutionary constraints of different taxonomic groups” argues Dr. Narimane Chatar who supervised this research project. “Frugivory, in contrast, provides a clearer example of different lineages repeatedly evolving similar dental transformations”.
Together, these findings clarify how much ecological information is preserved in carnivoran teeth and help define the contexts in which each analytical method is most appropriately applied.
Vankelst, M., Fischer, V., Michaud, M., Tamagnini, D., Pollock, T.I., Meloro, C., Tseng, Z.J,., and Chatar, N. (2026) Decoupling geometry and topography reveals contrasting ecomorphological signals in carnivoran carnassial teeth. Proceedings of the Royal Society B: Biological Sciences, 293 (2076): 20260400. https://doi.org/10.1098/rspb.2026.0400
Dr. Narimane Chatar (narimane.chatar@berkeley.edu)
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