Around 56 million years ago, during a period of significant geological warming known as the Paleocene-Eocene Thermal Maximum (PETM), the mesonychid mammal Dissacus Praenuntius exhibited remarkable dietary changes—it began to consume more bones.

“I am a doctoral student at Rutgers University in New Brunswick,” stated Andrew Schwartz from the University of New Jersey.

“We are observing a similar trend: rising carbon dioxide levels, increasing temperatures, and the destruction of ecosystems.”

In their study, Schwartz and his team analyzed small pits and marks left on fossilized teeth using a method known as dental microwear texture analysis. The research focused on the extinct mammal Dissacus Praenuntius, part of the Mesonychidae family.

This ancient omnivore weighed between 12 and 20 kg, comparable in size to jackals and coyotes.

Common in the early Cenozoic forests, it likely had a diverse diet that included meat, fruits, and insects.

“They resembled wolves with large heads,” Schwartz remarked.

“Their teeth were similar to those of hyenas, though they lacked small hooves on their toes.”

“Before this phase of warming, Dissacus Praenuntius mainly consumed tough meat, akin to a modern cheetah’s diet.”

“However, during and after this ancient warming period, their teeth showed wear patterns consistent with crushing hard substances like bones.”

“Our findings indicate that their dental microwear is similar to that of lions and hyenas.”

“This suggests they were consuming more brittle food rather than their usual smaller prey, which became scarce.”

This shift in diet occurred alongside a slight decrease in body size, likely a result of food shortages.

“While earlier theories attributed body size reduction solely to rising temperatures, this latest research indicates that food scarcity was a significant factor,” Schwartz explained.

“The rapid global warming of this time lasted around 200,000 years, but the changes it caused were swift and dramatic.”

“Studying periods like this can offer valuable lessons for understanding current and future climatic changes.”

“Examining how animals have adapted and how ecosystems responded can reveal much about what might happen next.”

“The research underscores the importance of dietary flexibility; species that can consume a variety of foods are more likely to endure environmental pressures.”

“In the short term, excelling in a specific area can be beneficial,” Schwartz added.

“However, in the long run, generalists—animals that are adaptable across various niches—are more likely to survive environmental changes.”

This understanding can assist modern conservation biologists in identifying vulnerable species today.

Species with specialized diets, like pandas, may struggle as their habitats diminish, while more adaptable species, such as jackals and raccoons, might thrive.

“We’re already starting to see these trends,” Schwartz noted.

“Previous research has shown that African jackals have begun to consume more bones and insects over time, likely due to habitat loss and climate stress.”

The study also indicated that rapid climate change, reminiscent of historical events, could lead to significant shifts in ecosystems, influencing prey availability and predator behaviors.

This suggests that contemporary climate change could similarly disrupt food webs, pushing species to adapt and face extinction risks.

“Nonetheless, Dissacus Praenuntius was a robust and adaptable species that thrived for about 15 million years before eventually going extinct,” Schwartz said.

Scientists believe this extinction was driven by environmental changes and competition with other species.

The study was published in June 2025 in the journal Paleogeography, Paleoclimatology, Paleoecology.

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Andrew Schwartz et al. 2025. Dietary Changes in Mesonychids During the Eocene Heat Maximum: The Case of Dissacus Praenuntius. Paleogeography, Paleoclimatology, Paleoecology 675:113089; doi:10.1016/j.palaeo.2025.113089