Beneath the snowy slopes lay a prehistoric surprise: an ecosystem that predates the dinosaurs, revealed by melting snow before being stumbled upon by a hiker in the Italian Alps.

The discovery, made public Wednesday, includes well-preserved footprints of reptiles and amphibians that scientists say date back 280 million years to a geologic period known as the Permian period.

“Dinosaurs had not yet emerged at this time, but the animals responsible for the largest footprints here would still…