About 56 million years ago, Earth underwent one of its most extreme periods of climate change, known as the Paleocene–Eocene Thermal Maximum (PETM). During this short but intense global warming event, temperatures soared, ecosystems shifted dramatically, and the survival strategies of many species were put to the test. A recent groundbreaking study led by researchers at Rutgers University has shed new light on the adaptability of ancient predators in this tumultuous era. By examining the fossilized teeth of the extinct mesonychid predator Dissacus praenuntius, scientists uncovered a striking dietary transformation that may reveal how prehistoric mammals coped with environmental upheaval—offering valuable insights into how modern wildlife might respond to accelerating climate change today.
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
