During the Mesozoic era, from 252 to 66 million years ago, analyses of the oxygen isotope composition in dinosaur teeth revealed that the atmosphere contained significantly more carbon dioxide than it does today, with global plant photosynthesis levels roughly double those of the present.
Fossil teeth of Camarasaurus from the Morrison Formation in the US. Image credit: sauriermuseum aathal.
A study conducted by Göttingen University and researcher Dr. Dingsu Feng examined the dental enamel of dinosaurs that roamed North America, Africa, and Europe during the Late Jurassic and Late Cretaceous periods.
“Enamel is one of the most stable biological materials,” they explained.
“It captures different oxygen isotopes based on the air dinosaurs inhaled with each breath.”
“The isotope ratios of oxygen reflect fluctuations in atmospheric carbon dioxide and plant photosynthesis.”
“This connection allows us to infer insights about the climate and vegetation of the dinosaur era.”
“During the late Jurassic, about 150 million years ago, the air contained four times more carbon dioxide than before industrialization, prior to significant human emissions of greenhouse gases.”
“In the late Cretaceous, around 730 to 66 million years ago, carbon dioxide levels were three times higher than today.”
Teeth from two dinosaur species, the Tyrannosaurus Rex and Kaatedocus siberi, showed an exceptionally unique oxygen isotope composition.
This phenomenon is indicative of carbon dioxide spikes linked to major geological events like volcanic eruptions—such as the massive eruption of the Deccan Traps in India at the close of the Cretaceous period.
The heightened photosynthetic activity of plants at that time on both land and water is likely associated with elevated carbon dioxide levels and higher average annual temperatures.
This research marks a milestone in paleoclimatology. Historically, soil and marine proxy carbonates have served as the primary tools for reconstructing past climates.
Marine proxies, which are indicators of sediment fossils and chemical signatures, help scientists comprehend ancient marine environmental conditions, yet these methods often involve uncertainties.
“Our approach offers a fresh perspective on the planet’s history,” Dr. Fenn remarked.
“It paves the way to use fossilized tooth enamel for probing the composition of Earth’s atmosphere and plant productivity during that era.”
“Understanding these factors is crucial for grasping long-term climate dynamics.”
“Dinosaurs may well become new climate scientists, as their teeth have recorded climate data for over 150 million years. At last, we have received their message.”
Study published on August 4, 2025, in Proceedings of the National Academy of Sciences.
____
Dingsu Feng et al. 2025. Mesozoic Atmospheric CO2 Concentrations reconstructed from the enamel of dinosaur teeth. PNAS 122 (33): E2504324122; doi: 10.1073/pnas.2504324122
Source: www.sci.news
