Scientists have discovered that dinosaur teeth hold an extraordinary record of Earth’s climate during the Mesozoic Era, between 252 and 66 million years ago.
By studying fossilized teeth, researchers found that carbon dioxide (CO₂) levels back then were far higher than today, helping to create a warm, dynamic “greenhouse” climate when dinosaurs thrived.
The international team—from the universities of Göttingen, Mainz, and Bochum—developed an innovative method to study the ratios of all three natural oxygen isotopes in tooth enamel.
This breakthrough gives scientists a new way to reconstruct ancient climates and vegetation, offering insights that were previously out of reach.
Their findings were published in the Proceedings of the National Academy of Sciences.
Tooth enamel is one of the hardest and most stable biological materials, preserving chemical signatures for millions of years.
The oxygen isotopes it contains come from the air a dinosaur breathed and the water it drank.
Because atmospheric CO₂ levels and plant photosynthesis influence the mix of oxygen isotopes in the air, these ratios can be used to understand both climate conditions and global vegetation activity in the past.
The researchers examined teeth from dinosaurs found in North America, Africa, and Europe, dating to the Late Jurassic and Late Cretaceous periods.
They discovered that about 150 million years ago, in the Late Jurassic, CO₂ levels were around four times higher than pre-industrial levels (before human-driven emissions began). In the Late Cretaceous, roughly 73 to 66 million years ago, CO₂ levels were about three times higher.
This warmer climate also supported much greater plant productivity—about twice the global yield of plants today.
That abundance of vegetation likely fueled rich and complex food webs, both on land and in the oceans, allowing ecosystems to support enormous species like sauropods and apex predators such as Tyrannosaurus rex.
Some teeth, including those from T. rex and the long-necked Kaatedocus siberi, showed unusual combinations of oxygen isotopes.
These anomalies may reflect sudden spikes in CO₂ caused by massive volcanic eruptions—such as those in the Deccan Traps of present-day India at the end of the Cretaceous period. Such eruptions could have drastically altered the atmosphere and climate in relatively short periods.
Until now, scientists studying ancient climates relied mostly on “marine proxies”—chemical clues preserved in ocean sediments—or on soil carbonates.
These sources give valuable information but come with uncertainties, especially when trying to understand conditions on land. This new tooth-based method is the first to focus on land-dwelling vertebrates, offering a clearer picture of life and climate on prehistoric Earth.
Lead author Dr. Dingsu Feng of the University of Göttingen explained, “Our method gives us completely new insights into Earth’s past. We can now use fossilized tooth enamel to study the atmosphere and the productivity of vegetation millions of years ago. Dinosaurs have become climate experts—their teeth recorded the climate more than 150 million years ago, and we can finally read that record.”
Co-author Professor Eva M. Griebeler from the University of Mainz emphasized that this research also provides rare evidence about ancient food webs. “The amount of plant biomass sets the limit for how many species an ecosystem can support and how long its food chains can be,” she said.
Paleontologist Professor Thomas Tütken added that the method also reveals the balance between oxygen from air and from drinking water in ancient animals, giving a deeper understanding of dinosaur biology.
By unlocking the climate records stored in dinosaur teeth, scientists now have a powerful new tool to explore how Earth’s atmosphere, ecosystems, and environments have changed over hundreds of millions of years.
