While countless species vanished, Lystrosaurus not only survived but thrived in a world marked by extreme environmental instability, intense heat, and prolonged droughts.

Now, groundbreaking research published in PLOS ONE reveals a discovery that transforms our understanding of this iconic survivor. An international team led by Professor Julien Benoit, Professor Jennifer Botha (Evolutionary Studies Institute, University of the Witwatersrand, South Africa), and Dr. Vincent Fernandez (ESRF—The European Synchrotron, France) has identified, for the first time, an egg containing an embryo of Lystrosaurus, dating back approximately 250 million years.

This extraordinary fossil represents the first-ever egg discovered from a mammal ancestor, finally answering a long-standing question: Did the ancestors of mammals lay eggs?

The answer is yes.

The researchers suggest these eggs were likely soft-shelled, explaining why they have remained elusive for so long. Unlike the hard, mineralized eggs of dinosaurs, which fossilize readily, soft-shelled eggs rarely preserve, making this find exceptionally rare. But the implications go far beyond reproduction.