The carnassial is the slicing hallmark of the order Carnivora, the modified cheek tooth pair that functions like a pair of scissors. In the upper jaw it is the last premolar, in the lower jaw the first molar, and together they shear flesh and other foods during each chewing stroke. Because these teeth meet blade against blade, their wear facets record the mechanical history of feeding with particular clarity. Dental microwear analysis samples these facets, ideally ones that occlude directly with one another, and uses the resulting texture to infer whether an animal was slicing tough meat, crunching bone, or processing a more varied diet. The method has become a standard tool for reconstructing the ecology of extinct mammals, from sabertooth cats to Pleistocene hyenas.

The practical problem that motivated the new research is one of scarcity. Fossil carnivore teeth are rare, and a usable analysis typically requires many individuals to reach statistically meaningful sample sizes. To maximize the number of usable observations, researchers routinely pool upper and lower teeth, treating the opposing, homologous wear facets as interchangeable. Previous work on fossil herbivores, however, had suggested that upper and lower teeth do not always carry identical wear signals, particularly when comparing facets that are not true functional counterparts. If the same discrepancy applies to carnivores, then pooling upper and lower carnassials could quietly contaminate dietary reconstructions with a methodological artifact.

Cecilia Loddi of the University of Florence and colleagues, including Riccardo Stefani, Lorenzo Rook, and Saverio Bartolini-Lucenti, set out to test whether the slicing portions of the upper and lower carnassials in living carnivores can genuinely be analyzed without distinction. Their question was precise: do the homologous wear facets of the upper and lower carnassials produce the same ecological evidence, or are they statistically distinct? To answer it, they turned to Dental Microwear Texture Analysis, or DMTA, a high-resolution technique that treats tooth surfaces as three-dimensional landscapes rather than flat images.

DMTA works by scanning a small patch of enamel at sub-micrometer resolution, producing a detailed topographic map of the wear surface. Software then quantifies that landscape using a set of parameters derived from scale-sensitive fractal analysis, known as SSFA attributes. These descriptors capture features such as surface complexity, roughness at different scales, heterogeneity, and the anisotropy of the texture, meaning the degree to which scratches run in a consistent direction. Complexity, for example, tends to rise when hard items like bone are processed, while anisotropy reflects the directionality of shearing movements. Together, the SSFA variables provide a numerical fingerprint of diet that can be compared across individuals, species, and, crucially for this study, across upper and lower teeth.

The team sampled four species of extant carnivores, examining the homologous wear facets of the slicing portion of the upper and lower carnassials in museum specimens. Working with modern animals whose diets are known is the essential calibration step: if upper and lower facets from animals with identical feeding habits were to show different textures, the difference could only come from the teeth themselves rather than from diet. The specimens were molded and cast following established replication techniques, and the resulting surfaces were scanned and characterized in the laboratory at the University of Florence, with the authors acknowledging curatorial and technical support from several European natural history museums in Basel, Paris, Berlin, Florence, and Munich.

The statistical approach is where the study distinguishes itself. Rather than simply running a null-hypothesis test and concluding that no difference was detected, the authors employed equivalence testing, a framework more familiar in psychology and clinical research than in paleontology. A conventional significance test can only fail to find a difference, which is not the same as demonstrating that two things are alike. Equivalence tests, such as the two one-sided tests procedure implemented in the TOSTER R package, flip the logic: they ask whether any observed difference is small enough to fall within a predefined zone of practical equivalence. Failing to reject a null hypothesis of no difference is weak evidence of sameness; formally rejecting the hypothesis of a meaningful difference is strong evidence of it.

By that stricter standard, the results were clear. Similarity tests found no statistically significant differences in the SSFA attributes between upper and lower homologous carnassial facets, and, more importantly, the parameters proved statistically equivalent. In other words, the texture signatures recorded on the upper carnassial and its lower counterpart carry the same ecological message, at least in the extant carnivores examined. The upper tooth really is the lower tooth, at least as far as microwear is concerned, and the old pooling practice survives its first formal challenge in this group.

The practical implications reach well beyond the four study species. If upper and lower carnassial facets can be combined without distortion, every fossil jaw fragment bearing either tooth becomes admissible evidence, effectively doubling the pool of available data for a given fossil assemblage. For groups where sample sizes have always been the bottleneck, this is a substantial gain. Fossil carnivores are notoriously underrepresented in microwear studies compared with the richer herbivore record, and the authors highlight this data scarcity as a central obstacle to reconstructing the dietary ecology of ancient predators. A validated doubling of usable teeth could make previously marginal assemblages analytically viable.

Some caveats remain and are worth keeping in view. The equivalence demonstrated here applies to homologous, occluding facets of the slicing carnassial in extant carnivores; earlier work on herbivores suggests that non-homologous facets and other tooth positions may behave differently, so researchers should not assume the result generalizes beyond the specific pair of surfaces tested. Extending the analysis to a broader range of carnivore species, and eventually to fossil taxa themselves, would strengthen the conclusion. Even so, the study converts a long-standing convenience into a validated protocol, giving paleontologists a firmer statistical footing the next time they combine an upper carnassial with a lower one to reconstruct what an ancient predator ate.

Subject of Research: Equivalence of dental microwear texture patterns between upper and lower carnassial teeth in extant carnivores

Article Title: Up is down: testing the equivalence in dental wear patterns of the upper and lower carnassial

Article References: Loddi, C., Stefani, R., Rook, L., & Bartolini-Lucenti, S. (2026). Up is down: testing the equivalence in dental wear patterns of the upper and lower carnassial. The Science of Nature, 113(5), Article 110. https://doi.org/10.1007/s00114-026-02158-4

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02158-4

Keywords: dental microwear, Dental Microwear Texture Analysis, carnassial, Carnivora, paleoecology, tooth wear, SSFA, equivalence testing, diet reconstruction, fossil carnivores, wear facets, paleontology

The research team employed Dental Microwear Texture Analysis (DMTA), a sophisticated technique that examines microscopic wear patterns on the molar surfaces of teeth to reconstruct an animal’s recent dietary habits. These surface features—comprising intricate scratches and pits—serve as a biological archive of the “last supper” in an individual wolf’s lifetime, revealing the nature of consumed materials. By applying DMTA to wolf teeth from distinct historical intervals, the researchers could deduce shifts in dietary hardness linked to climatic fluctuations.

Samples examined span three pivotal periods: approximately 200,000 years ago, reflective of an interglacial climate with summer conditions akin to the present but characterized by colder winters; circa 125,000 years ago, an epoch notable for elevated summer temperatures and milder winters; and contemporary wolves inhabiting Poland, a region currently experiencing noticeable warming winters and diminished snow cover. These timeframes offer a temporal gradient for assessing how wolves adjusted their foraging strategies in response to environmental pressures.

Analysis of the fossilized dentition revealed marked differences between wolves from the older and younger interglacial epochs. Specifically, molar microwear data indicate that earlier wolves consumed relatively softer diet components, whereas wolves from the younger, warmer interglacial period exhibited increased durophagy, reflected in more extensive tooth surface abrasions consistent with bone consumption. This dietary shift suggests that warmer climates exerted ecological stress, compelling wolves to exploit harder, less digestible food sources more intensively.

Intriguingly, modern wolves from Poland exhibit dental microwear patterns remarkably similar to those of the younger interglacial wolves, underscoring that ongoing climate warming is generating comparable ecological challenges today. This congruence reveals that contemporary wolf populations are under previously unrecognized stress, likely driven by reduced snow cover and altered prey availability caused by global climate trends.

The underlying ecological mechanism relates closely to snow conditions. Snow-covered landscapes traditionally favor predator efficiency by limiting herbivore mobility and concealing them from foraging challenges, thereby enhancing wolf hunting success. Heavier snow cover results in higher prey vulnerability and supports greater predator body condition and litter survival. Conversely, warmer winters with sparse snow reduce these advantages, making wolves’ hunting efforts more energetically costly and less fruitful.

To cope with these disadvantages, wolves appear to compensate by scavenging more extensively, frequently consuming carcass bones and other tough tissues normally avoided under optimal conditions. This behavioral plasticity involves greater energetic expenditure and could increase exposure to risks associated with scavenging, such as pathogen transmission and conflict with other scavengers or humans.

Moreover, in human-modified landscapes like parts of Poland, wolves have adapted by incorporating food sources such as deer and wild boar near agricultural areas, as well as roadkill. Paradoxically, populations situated in more pristine habitats might suffer disproportionately from climate-driven stress due to limited access to such anthropogenic subsidies, raising conservation concerns for wolves residing in wilderness regions.

This research harnesses the value of fossil collections held at institutions like the Natural History Museum in London, some specimens dating back over 175 years, exemplifying how palaeontological archives can illuminate modern conservation issues. By bridging paleobiology and ecological science, the emerging discipline of conservation palaeobiology promises to integrate long-term natural history perspectives into wildlife management amidst rapid environmental change.

The study’s authors argue that long-term conservation strategies for large carnivores must integrate considerations of climate dynamics, as rising temperatures and altered seasonality pose substantive risks to predator populations historically adapted to cold, snowy conditions. Recognizing such climatic stressors will be essential to designing effective recovery and management plans for wolves facing a warming future.

This innovative research, led by the University of Bristol in collaboration with the Natural History Museum and other institutions, was supported by the Natural Environment Research Council (NERC) and involved international partners including the University of Warsaw and the University of Leicester. It highlights a vital intersection between climate science, ecology, and conservation biology, offering a model for future investigations aimed at understanding and mitigating biodiversity impacts from global change.

Study co-author Professor Danielle Schreve emphasizes the significance of these findings: “Our analysis provides compelling evidence that grey wolves’ feeding ecology is intimately linked to climate variability, challenging the perception of their resilience. This underscores the necessity for conservation policies that acknowledge and address the subtle but profound impacts of warming climates on apex predators.”

Similarly, lead author Dr. Amanda Burtt highlights the intricacies of the dietary adjustments wolves make in the face of warming: “The transition to consuming harder foods such as bones indicates heightened ecological stress, revealing wolves’ attempts to extract maximal nutrition under increasingly challenging environmental conditions. This insight is crucial for anticipating how ongoing climate shifts may affect predator-prey dynamics and ecosystem health.”

With global climate change accelerating, comprehending the nuanced biological responses of keystone species like grey wolves is indispensable. This study adds to a growing body of evidence that terrestrial carnivores are not insulated from climate-driven perturbations. Instead, they are enmeshed in complex adaptive behaviors that have consequences extending beyond their populations to the broader ecological communities they shape.

In conclusion, this research elucidates a critical, previously underappreciated dimension of climate change impacts: the modification of feeding behavior in response to thermal and seasonal shifts. The demonstration that grey wolves increase bone consumption during warmer interglacial periods and current warming trends signifies an adaptive yet costly behavioral strategy. This finding serves as a clarion call for conservationists and policymakers to incorporate climate change resilience measures explicitly into plans safeguarding wolves and other large carnivores throughout their ranges.

Subject of Research:
Grey Wolf dietary adaptation and ecological stress in response to climate change, using Dental Microwear Texture Analysis across historical and modern populations.

Article Title:
Climate Change Challenges Grey Wolf Resilience: Insights From Dental Microwear

News Publication Date:
11-Feb-2026

Web References:
https://onlinelibrary.wiley.com/doi/10.1111/ele.70337
http://dx.doi.org/10.1111/ele.70337

Image Credits:
Amanda Burtt

Keywords:
Climate change, Animal ecology, Dental Microwear Texture Analysis, Grey wolf, Durophagy, Conservation palaeobiology, Ecological stress, Apex predator, Interglacial periods, Predator-prey dynamics

Utilizing the cutting-edge technique known as dental microwear texture analysis, the research team meticulously deciphered the microscopic wear patterns preserved on the teeth of Dissacus. This method explores the intricate pits and scratches etched into enamel surfaces, which serve as direct indicators of an animal’s recent diet before death. Previously, it was posited that Dissacus had a carnivorous diet resembling that of modern cheetahs, focusing largely on flesh from relatively small prey. However, the microwear signatures uncovered in this study indicate that during and following the PETM, Dissacus began consuming harder, more brittle materials—presumably bones—marking a significant shift toward osteophagy, or bone-eating behavior. This adaptation likely emerged as a response to a scarcity of typical prey, itself a consequence of the climate-driven disruptions to local ecosystems.

The importance of this behavioral flexibility cannot be overstated. The team’s findings suggest that Dissacus was neither a specialized predator nor a strict scavenger but rather a dietary generalist capable of expanding its food sources to survive in changing conditions. Such plasticity in feeding strategies might have been pivotal in enduring the approximately 200,000-year interval of elevated temperatures and ecological instability during the PETM. Notably, this adaptive shift also coincided with a modest reduction in body size for Dissacus, a phenomenon that corroborates previous hypotheses linking mammalian dwarfism to climate stress but emphasizes that food availability and nutritional quality also played critical roles in driving evolutionary responses.

The PETM represents one of the most rapid and profound warming events in Earth’s recent geological history, marked by a roughly 5 to 8 degrees Celsius rise in global temperatures over just a few thousand years. This rapid shift led to widespread habitat alteration, species migrations, and extinctions. Within this setting, the study’s findings are particularly salient; they show how gradual dietary adjustments could buffer some species against extinction pressures by widening their ecological niches. The parallel to today’s climate crisis is clear and alarming: as modern ecosystems face unprecedented temperature increases and habitat degradation, species able to adapt their resource use may stand a better chance of survival amid ongoing environmental stressors.

Researchers also emphasize that the behavioral experiment observed in Dissacus is echoed in contemporary carnivores grappling with habitat loss and climate variability. For example, modern jackals in Africa have exhibited increased bone and insect consumption, behaviors seemingly driven by the shrinking of their traditional prey base and altered ecosystems. This convergence of paleoecological evidence and present-day observations underscores the continuity of nature’s responses to warming climates and the critical relevance of paleontological data for forecasting future biodiversity outcomes.

The technique of dental microwear texture analysis used in this study represents a powerful tool in paleontology, allowing scientists to peer into the lifeways of long-extinct animals with unprecedented resolution. By quantifying textures on fossil teeth, researchers reconstruct diets and ecological interactions millions of years old, overcoming the limitations of morphological inference alone. This level of dietary reconstruction provides deep insight into how evolutionary pressures shape species over time and offers a window into the ecology of vanished ecosystems—key to understanding the ongoing dynamics of biosphere responses to climate.

Dissacus praenuntius itself was an enigmatic mammal, about the size of a modern jackal or coyote, belonging to the mesonychid group—an extinct lineage of carnivorous ungulates known for their hyena-like teeth. These animals possessed unique adaptations such as tiny hooves on their toes, a blend of traits hinting at their complex evolutionary history and diverse ecological roles. Their long tenure across the Paleocene and Eocene epochs, spanning some 15 million years, signifies their success in weathering multiple environmental challenges, though ultimately, they too succumbed to changing conditions and competition by the Eocene’s close.

The fossils that informed this research were excavated from the Bighorn Basin in Wyoming, a site renowned for its exceptionally continuous sedimentary record that captures detailed environmental and faunal changes through the Paleocene and Eocene. This locality provides an unparalleled natural archive, allowing researchers to pinpoint subtle shifts in climate, habitat, and species behavior against a finely resolved timeline—a critical advantage in teasing apart the mechanisms behind evolutionary transitions during climate upheavals.

Co-led by Andrew Schwartz, a doctoral student specializing in anthropology and paleontology, and Associate Professor Robert Scott, the Rutgers team collaborated with experts including Larisa DeSantis from Vanderbilt University to integrate their diverse expertise in fossil analysis and environmental reconstruction. Their work underscores a multidisciplinary approach combining field excavation, laboratory microscopy, and ecological modeling to unravel the complex story of animal adaptation to planetary warming.

The implications of this research extend beyond academic interest, suggesting tangible strategies for conservation biology. Species exhibiting dietary specialization face greater extinction risks under climate change, whereas generalists might buffer themselves by exploiting alternative food sources. Consequently, conservation efforts might prioritize support for vulnerable specialists—like the giant panda—as their habitats shrink, whilst recognizing the potential resilience of adaptable omnivores such as raccoons and jackals. Moreover, fossil evidence of past resilience and vulnerability can inform proactive management to mitigate biodiversity losses in a rapidly warming world.

Ultimately, evolutionary stories like that of Dissacus praenuntius highlight the intricacy of life’s response to environmental challenges. As Dr. Schwartz emphasizes, understanding past biological adaptations not only enriches our knowledge of Earth’s history but equips us with vital lessons applicable to current and future conservation efforts. The interplay between climate, ecology, and evolution remains a dynamic narrative, offering hope that adaptability and flexibility might yet allow life to endure through the coming decades of global change.

Subject of Research: Not applicable

Article Title: Dietary change across the Paleocene-Eocene Thermal Maximum in the mesonychid Dissacus praenuntius

News Publication Date: 17-Jun-2025

Web References:
https://www.sciencedirect.com/science/article/pii/S0031018225003748?via%3Dihub

References:
Palaeogeography, Palaeoclimatology, Palaeoecology, DOI: 10.1016/j.palaeo.2025.113089

Image Credits: ДиБгд, CC BY 4.0 via Wikimedia Commons

Keywords: Fossils, Tertiary period