Unusual ancient elephant tracks had our team of fossil experts stumped—how we solved the mystery

Over the past 15 years, through our scientific study of tracks and traces, we have identified more than 350 fossil vertebrate tracksites from South Africa's Cape south coast. Most are found in cemented sand dunes, called aeolianites, and all are from the Pleistocene Epoch, ranging in age from about 35,000 to 400,000 years.

During that time we have honed our identification skills and have become used to finding and interpreting tracksites—a field called ichnology. And yet, every once in a while, we encounter something we immediately realize is so novel that it has been found nowhere else on Earth.

Such a moment of unexpected discovery happened in 2019 along the coastline of the De Hoop Nature Reserve, about 200km east of Cape Town. Less than two meters away from a cluster of fossil elephant tracks was a round feature, 57cm in diameter, containing concentric ring features. Another layer was exposed about 7cm below this surface. It contained at least 14 parallel groove features. Where the grooves approached the rings, they made a slight curve towards them. The two findings, we hypothesized, were connected with each other and appeared to have a common origin.