Telltale Teeth 

Dinosaur fossils are valuable artifacts, providing clues to how those creatures lived, what they ate, and what other beasts they were related to. 

Now, a new study of fossilized dinosaur teeth is providing information on their environment. Shedding new light on the climate of early Earth, it suggests that humans may have struggled to breathe had they lived alongside dinosaurs. 

“Long ago, their teeth recorded the climate for a period of over 150 million years – finally we are getting the message,” said lead study author Dingsu Feng in a statement. 

For the study, researchers analyzed tooth enamel from dinosaurs found in North America, Africa, and Europe dating from the late Jurassic and late Cretaceous periods. 

Tooth enamel – the hard, outer layer of the tooth that protects its inner parts – is one of the most stable biological materials and can preserve oxygen isotopes from a dinosaur’s environment. With every breath, bite of food, and sip of water, oxygen from the air, food, and water became part of their teeth. 

Examining oxygen isotopes in that material, the researchers found that the atmosphere during the Mesozoic era, between 252 and 66 million years ago, contained far more carbon dioxide than it does today. 

In the late Jurassic period, about 150 million years ago, carbon dioxide levels in the atmosphere were roughly four times higher than they were before industrialization, meaning before humans began releasing greenhouse gases in large amounts. 

In the late Cretaceous, about 73 to 66 million years ago, carbon dioxide levels were three times as high as today. 

Researchers said the balance of isotopes in oxygen is influenced by factors such as atmospheric carbon dioxide levels and plant photosynthesis, a correlation that enables scientists to reconstruct the climate and plant life that existed during the dinosaur age. 

Individual teeth from two dinosaurs – Tyrannosaurus rex and Kaatedocus siberi, a relative of Diplodocus – showed an unusual pattern of oxygen isotopes.  

This suggests sudden increases in CO2 levels that may be connected to major events like volcanic eruptions, such as the huge Deccan Traps eruptions that took place at the end of the Cretaceous in present-day India. 

The total photosynthesis from plants on land and in water around the world was twice as high as it is today, likely due to CO2 levels and higher average annual temperatures. 

This study represents a significant breakthrough in paleoclimatology. Until now, to reconstruct past climates, scientists mainly relied on soil carbonates and “marine proxies” – indicators like fossils or chemical traces in ocean sediments.  

Examining oxygen isotopes in fossilized teeth is a new approach, providing the first climate reconstruction method based on land vertebrates. 

“Our method gives us a completely new view of the Earth’s past,” said Feng. “It opens up the possibility of using fossilized tooth enamel to investigate the composition of the early Earth’s atmosphere and the productivity of plants at that time. This is crucial for understanding long-term climate dynamics.”