A world scrubbed clean
Around 252 million years ago, life on Earth almost ended. The Permian-Triassic extinction event, or "the Great Dying," was the most severe extinction in the planet's history. It eliminated about 81% of marine species and 70% of terrestrial vertebrate species. In the aftermath, the world was a strangely empty place. The complex ecosystems of the Permian had collapsed, leaving a simplified and harsh landscape.
It is in this recovering world that the story of these footprints begins. The tracks are preserved in the layers of the Buntsandstein, a geological formation of reddish sandstone prominent in central Germany. During the Early Triassic, this region was part of the supercontinent Pangaea's interior. The environment consisted of arid, continental basins with playa lakes, rivers, and salty sandflats. The red color of the rock comes from iron oxide, a result of the hot and dry climate. It was across these muddy, sun-baked flats that small, resilient reptiles walked, leaving behind a record of life's return.
The survivors' signature
Ichnology, the study of trace fossils, shows this post-apocalyptic world. Unlike body fossils, which tell us about an animal's anatomy, trace fossils like footprints record an organism's behavior. The tracks found in Thuringia's Buntsandstein are dominated by ichnogenera such as Rhynchosauroides and Procolophonichnium. These are the scientific names for the fossil tracks themselves, not the animals that made them.
Based on the shape and size of these pentadactyl (five-toed) prints, scientists can infer the trackmakers. They were likely small, lizard-like diapsid reptiles—the ancestors of modern lizards, snakes, and crocodiles. The tracks of Procolophonichnium are attributed to procolophonids, a group of small, stocky parareptiles. These creatures were not giant rulers of the coming ages; they were small survivors. The ecosystem they inhabited was unstable, prone to boom-and-bust cycles that delayed a full recovery for up to 8 million years. The footprints in the German sandstone capture the first steps of this long recovery, documenting the pioneers of a new era.