IPC7 committee member leads discovery of first soft-shelled eggs of a mammalian forerunner

Prof Julien Benoit, a member of the organising committee of the 7th International Palaeontological Congress (IPC7) was deeply involved in a new PLoS One paper that deciphers the importance of a fist-sized fossilised embryo found in South Africa 17 years ago. Its discovery shows that Lystrosaurus, a pig-sized plant-eating animal with a beak-like mouth and a forerunner of today’s mammals, did in fact lay soft-shelled eggs.

At IPC7, Prof Benoit, of the Evolutionary Studies Institute at the University of the Witwatersrand in South Africa, is a co-host of the Palaeoneurology symposium and will present a session about the significance and context of this finding.  

He was lead author of the PLoS One, which was published in April 2026. His co-authors were Prof Jennifer Botha of the Evolutionary Studies Institute at the University of the Witwatersrand, and Director of GENUS, a South African Department of Science, Technology and Innovation-National Research Foundation funded Centre of Excellence in Palaeosciences and Dr Vincent Fernandez of the European Synchrotron Radiation Facility (ESRF).

Dr Fernandez was responsible for detailed three-dimensional synchrotron scans of the egg. It shows that a tiny 5cm-long Lystrosaurus found within a nodule was in fact an embryo lying within what once was a leathery, soft-shelled egg. Its jaw was not yet fused, indicating that it was still underdeveloped at the time that the animal died and would not have been able to fend for itself. The large size of the egg itself indicates that it was a precocial animal that would not need much parental care after being hatched.

“Monotremes such as platypus lay small eggs because the embryo is not fed yolk, but milk after it is born. In contrast, Lystrosaurus’ large egg indicates there was enough yolk inside and no need of milk post-hatching,” says Prof Benoit.

The fossilized egg was found in 2008 on a farm in South Africa’s Eastern Cape province by the late John Nyapuli, a legendary figure in South African palaeontology who worked at the National Museum in Bloemfontein. He was accompanied by Prof Botha, back then also of the National Museum, whose hunch that it might be a Lystrosaurus egg was confirmed with the synchrotron scans.

The scanning of the nodule forms part of a larger project that Prof Benoit leads on the evolution of brain size, behaviour and adaptation as a survival mechanism through the devastating Permo-Triassic Mass Extinction (PTME) and beyond. Together with Prof Botha and Dr Fernandez, he hopes to shed new light on the evolutionary response of the central nervous system of ancient animals to high-stress extinction conditions, and how such dramatic events shaped the mammalian brain. More than 100 scans of Lystrosaurus, an animal that survived beyond the PTME of 252 million years ago, and other comparative species have already been completed.