What fossil tooth wear reveals about ancient mammals during rapid warming
During an ancient bout of severe global warming, three lineages of early hoofed mammals shrank in size but kept their diets surprisingly stable.
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The full story with proper science words explained.
A climate crisis 56 million years ago
Imagine your entire local environment drying out while temperatures soar. That happened 56 million years ago during the Paleocene-Eocene Thermal Maximum, or PETM. This sudden warming event triggered massive floral turnover, replacing many familiar regional plant species with new ones.
Faced with this upheaval, early hoofed mammals in Wyoming's Bighorn Basin underwent dramatic evolutionary shifts. Species of Copecion, Ectocion, and the early horse relative Sifrhippus underwent phylogenetic dwarfing, shrinking considerably over generations. But did this ecological shake-up also force them to abandon their favourite foods?
Reading ancient meals
To find out, researchers turned to fossil tooth wear. Food leaves tiny microscopic pits and scratches on enamel. Hard seeds create complex, jagged pits, whereas soft leaves leave smoother surfaces. Scientists used dental microwear texture analysis (DMTA) to scan these 3D microscopic textures on fossilised teeth.
The team tracked surface complexity, scale of maximum complexity, and textural fill volume across the warming event. They discovered that both phenacodontids—an extinct group of primitive hoofed mammals—fed as frugivorous mixed feeders, eating fruits alongside other plant tissues. Meanwhile, Sifrhippus showed tooth surfaces that matched strong, dedicated fruit eating.
Stubborn eaters
Remarkably, these dietary habits stayed largely stable right across the PETM. Even as forests transformed, these mammals sought out similar types of meals. The study does not claim diet was entirely static across every metric, but shifts were minor and limited to textural fill volume in Ectocion.
What we still don't know
Fossil textures reveal how hard or tough food was, not the exact botanical species on the menu. We also do not know whether mammals living outside the Bighorn Basin managed to stick to their diets so persistently. Even so, these ancient teeth suggest that some animals can maintain their feeding habits even during extreme climate breakdown.
Science words
- Paleocene-Eocene Thermal Maximum (PETM)
- A sudden global warming and drying event that took place roughly 56 million years ago.
- Floral turnover
- A major change or replacement in the types of plant species living in an ecosystem.
- Phylogenetic dwarfing
- An evolutionary decrease in average body size within a species lineage over generations.
- Dental microwear texture analysis (DMTA)
- A method measuring 3D microscopic pits and scratches on teeth to identify what an animal ate.
- Phenacodontids
- An extinct group of early, primitive hoofed mammals.
- Textural fill volume
- A measurement of the physical volume of microscopic spaces and features on a tooth surface.
Check it yourself
This story is based on a real research paper in Ecology and Evolution by Schwartz, DeSantis, Scott. We write with AI help and check it against the paper, but the original is the final word.