Of crocodiles, counting and conferences

(Press-News.org) Growth marks are like “’tree rings”

“Many vertebrates grow in a cyclical manner. This leaves definable growth marks in their bones, and is similar to tree rings,” explains Prof Chinsamy-Turan, an expert on deciphering biological signals in the bone microstructure of extinct and extant vertebrates. 

Researchers have used these rings to estimate the minimum age of extant and extinct amphibians, mammals, birds and reptiles; a study termed skeletochronology. Using this information, they deduce growth curves and so learn more about the growth dynamics and life history of an animal.

To test this technique on crocodiles, the research duo investigated slices of bone of four two-year-old crocodiles raised together under similar circumstances. Under the microscope they saw very clear growth marks in dense, compact parts of the two-year old animals’ bones – but many more than were expected for crocs of that age. Added to this, the “extra” growth marks did not merely correspond to yearly growth. The “extras” presumably were laid down during favourable growing periods possibly related to environmental factors such as competition for food, dominance or extreme heat.

Had the UCT research duo only counted the number of visible growth marks in the bones of the two-year-old animals they studied, they would have overestimated the age of the crocs in the Scientific Reports paper at between 5 and 6 years old.

Growth rates not fixed

The fact that growth marks varied so much within the bones of the young crocodiles shows that their growth is flexible and can change depending on environmental conditions.

“Many vertebrates, including alligators and newts, similarly change their relative growth rates in response to environmental conditions,” notes Dr Pereyra, an Argentinian postdoctoral researcher based at UCT.

What do the findings mean for dinosaur research?

Prof Chinsamy-Turan says such flexibility is likely to have been present too in a wide variety of extinct vertebrates, especially those closely related to crocodiles, such as dinosaurs. Palaeontologists often study the microstructure of dinosaur bones to among others better understand how long it took before they were fully grown.

Based on their results, Prof Chinsamy-Turan and Dr Pereya caution against using growth marks and derived growth curves to age modern-day animals as well as 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,” they advise.

Bringing the international paleontological congress to Africa for the first time

Their latest Scientific Reports paper is already the fourth published since Dr Pereyra joined Prof Chinsamy-Turan’s research group three years ago. One of these was in the Journal of Anatomy, on an extinct small, long-necked marine reptile whose fossilised remains were recovered in Argentina. Two others, in the Journal of Morphology, focused on broad-snouted caimans from Argentina.

In between their research work, they are working closely on another major endeavour: to bring the 7th International Palaeontological Congress (IPC7) to Africa – and to Cape Town – for the first time.

The University of Cape Town will host IPC7 from 30 November to 3 December 2026. The conference, the signature event of the pre-eminent International Palaeontological Association (IPA), is only held every four years. It will see the who’s who of the palaeontology world at large gather in venues such as the Baxter Theatre, the Neville Alexander Building and the Iziko SA Museum in Cape Town. Thirty different themes will be tackled through dedicated symposia on all aspects of palaeontology. These delve into finds from the Archean to the Holocene, and cover work from all continents. Recent findings across all the distinct prehistoric ages will be discussed, along with topics such as disease in the fossil record, the evolution of flight in vertebrates, recent advances in the study of dinosaur eggs and reproduction, and African vertebrates of the Cenozoic geological era.

Prof Chinsamy-Turan steers the local organising committee as chair, while Dr Pereyra is in charge of the IPC7s active social media channels. Other UCT staff and students serving on the LOC are Dr Miengah Abrahams, Dr Yonatan Sahle Chemere, Andrea Plos, and Caitlin Rabe. They are supported by local palaeontologists from the University of the Witwatersrand, Albany Museum and the Iziko SA Museum.

The team has already reached important milestones, with registration recently opened  and plenary speakers already announced.

Dr Pererya is co-organising a symposium on mineralised tissues, while Prof Chinsamy-Turan is co-organising two symposia: on disease in the fossil record, and on communicating palaeosciences to the wider community.

“The latter is integrated directly as part of the main conference, not as an ‘add-on’, and has so far been very well received. It is so important that as scientists we communicate our findings to the wider public,” says Prof Chinsamy-Turan, a well-known public speaker on all things palaeontologic, and the author of popular level books on dinosaurs and other prehistoric life.

A preconference field trip is planned to the West Coast Fossil Park near Langebaan, a rich Miocene/Pliocene site where many current and former UCT staff members and alumni have made significant findings. Notable is Lokotunjailurus chinsamyae, a recently described sabre tooth cat named after Prof Chinsamy-Turan. Other field trips will head into the Cederberg and the Karoo or will visit famous sites near Makhanda or dinosaur stomping grounds. Other trips to Table Mountain and the Maropeng Cradle of Humankind are also possible.

“Delegates should also consider visiting the collections at many museums across South Africa while they are visiting the country,” advises Dr Pereyra.

“While we already have funding for some travel grants for researchers and postgraduate students from Africa, Argentina and elsewhere, we hope to announce more soon,” says Prof Chinsamy-Turan.

 

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