A 250-million-year-old fossil reveals an unlikely Triassic friendship in a burrow

Nature · Published 3 October 2026 Swipe more like this →

In short: In 1975, paleontologist James Kitching unearthed a fossilized pair of ancient creatures huddled together in a South African burrow. This Triassic-era discovery, featuring a small protomammal and an injured amphibian, offers a rare, intimate look at survival strategies during the blistering heat of the Early Triassic period.

The fossilized pair consists of a Thrinaxodon, a small, fox-sized cynodont, and a Broomistega, a salamander-like amphibian. Discovered near South Africa’s Oliviershoek Pass, the remains were found within a burrow that likely served as a refuge from the harsh, dry conditions of the Early Triassic, a period spanning roughly 251 to 200 million years ago. While the Thrinaxodon was likely the primary occupant of the den, the presence of the Broomistega suggests a unique instance of interspecies cohabitation.

Advanced synchrotron scanning at the European Synchrotron Radiation Facility in Grenoble, France, revealed the pair in stunning articulation. Researchers hypothesize that the Broomistega, suffering from broken, healing ribs that would have severely limited its mobility and breathing, sought shelter in the burrow. The Thrinaxodon, meanwhile, was likely in a state of aestivation—a multi-day, torpor-like slumber—which allowed the two animals to share the cool, dark space without conflict. They were eventually entombed together by a sudden influx of water and sediment.

This discovery is significant for understanding the behavior of early synapsids. Thrinaxodon is a key transitional fossil, showing a reduction in skull bone complexity compared to its ancestors and possessing a secondary palate that allowed it to breathe while eating. Though the Broomistega bore puncture marks, their size and spacing did not match the Thrinaxodon’s teeth, suggesting the two lived in a rare, peaceful proximity. Their final resting place provides a poignant glimpse into the challenges of life 250 million years ago, where injury and climate forced unlikely neighbors into a shared, eternal repose.

The study of these fossils, published in 2013, highlights the importance of non-invasive imaging in paleontology. By peering through the stone without damaging the specimens, scientists could confirm the anatomical details of both creatures and reconstruct the circumstances of their burial. This rare snapshot of ancient life remains one of the most compelling examples of animal behavior preserved in the fossil record.

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