Cape Town scientists say we might be wrong about dinosaur ages
Anusuya Chinsamy-Turan and Maria‑Eugenia Pereyra from the University of Cape Town say growth marks in crocodile bones may not accurately reveal the age of reptiles or dinosaurs.
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Two University of Cape Town researchers are challenging a long-standing scientific method used around the world to estimate the age of crocodiles and dinosaurs.
In a study published in Scientific Reports, Anusuya Chinsamy-Turan and Maria‑Eugenia Pereyra from the Department of Biological Sciences at University of Cape Town found that growth marks in crocodile bones cannot be reliably used to determine age.
For decades, scientists have used a technique known as skeletochronology to estimate the age of animals. The approach works on the assumption that growth marks in bones form annually, much like rings in a tree trunk.
But the UCT team’s research suggests the process may be far more complex.
“Many vertebrates grow in a cyclical manner. This leaves definable growth marks in their bones, and is like tree rings,” explained Chinsamy-Turan, an expert in analysing biological signals preserved in bone microstructure.
To test the method, the researchers examined bone slices from four two-year-old Nile crocodile specimens that had been raised under similar conditions. Under the microscope, they found significantly more growth marks in the bones than expected for animals of that age.
Had they relied only on counting the visible rings, the crocodiles would have appeared to be between five and six years old.
The additional marks likely formed during favourable growth periods rather than once a year, possibly triggered by environmental factors such as competition for food, dominance or extreme heat.
The findings suggest that growth rates in reptiles are flexible and influenced by environmental conditions.
“Many vertebrates, including alligators and newts, similarly change their relative growth rates in response to environmental conditions,” Pereyra said.
The implications extend far beyond crocodiles.
Palaeontologists frequently analyse the microstructure of fossil bones to better understand the growth patterns and life histories of extinct animals, including dinosaurs. If growth marks do not correspond strictly to yearly cycles, the method could lead to inaccurate estimates of age.
Based on their findings, the researchers caution against using growth marks and derived growth curves as a definitive way to determine the age of both modern animals and extinct vertebrates.
“It is better to think of growth marks seen in the dense outer part of bones as signs of intermittent periods of growth rather than marks that consistently formed once each year,” Pereyra said.
The study is the fourth paper published by Pereyra and Chinsamy-Turan since the Argentinian postdoctoral researcher joined the UCT research group three years ago.
Beyond their research, the pair are also working on a bid to bring the 7th International Palaeontological Congress to Africa for the first time, with Cape Town proposed as the host city.
If successful, it would mark the first time the global gathering of palaeontologists is held on the continent.