Thursday, 12th of March, 2026

UCT scientists say growth rings in reptile bones may not reliably determine age, raising new questions about how palaeontologists estimate dinosaur lifespans.

Scientists at the University of Cape Town are raising new questions about a widely used scientific technique that has shaped how researchers estimate the age of reptiles and even dinosaurs.

The study, published in the international journal Scientific Reports, was conducted by Professor Anusuya Chinsamy-Turan and postdoctoral researcher Maria-Eugenia Pereyra from the Department of Biological Sciences at the University of Cape Town.

For decades, palaeontologists and zoologists have relied on a method known as skeletochronology to estimate the age of animals. The technique works on the assumption that growth marks found in bones form once per year, similar to the rings that appear in the trunk of a tree.

By counting these rings, scientists have attempted to reconstruct the growth rates and life histories of animals, including extinct species such as dinosaurs.

However, the new research from Cape Town suggests the process may not be as straightforward as previously believed.

To test the reliability of the method, the researchers analysed thin sections of bone taken from four Nile crocodiles that were known to be two years old and had been raised under similar environmental conditions.

When examined under a microscope, the bone samples revealed significantly more growth marks than expected for animals of that age.

If scientists had relied purely on counting these marks, the crocodiles would have appeared to be between five and six years old, more than double their actual age.

The findings suggest that growth marks in reptile bones may form during periods of favourable growth, rather than strictly once every year.

Environmental factors such as food availability, competition, social dominance and extreme temperatures may influence how frequently these marks appear.

This has important implications for palaeontology, as researchers often study the microstructure of fossilised bones to determine the age and growth patterns of extinct animals.

If growth rings do not consistently represent annual cycles, scientists may need to reconsider how they interpret bone evidence when reconstructing the life histories of dinosaurs and other prehistoric species.

The research team says growth marks should instead be viewed as indicators of intermittent growth periods, rather than reliable annual markers.

Beyond their current work, the UCT researchers are also involved in a bid to bring the 7th International Palaeontological Congress to Cape Town.

If successful, the event would mark the first time the global gathering of palaeontologists is held on the African continent, positioning Cape Town as a major host for international scientific collaboration.

Source: IOL – Murray Swart

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