Thousands of dinosaur footprints, some as wide as 40cm and complete with toes and claw marks, have been discovered by chance in the Italian Alps by a wildlife photographer who was stalking deer.

The footprints cover a near-vertical rock face in a remote snowy part of Stelvio national park in the Lombardy region, which will host the 2026 Winter Olympics.

“This set of dinosaur footprints is one of the largest collections in all of Europe, in the whole world,” said Attilio Fontana, head of the region.

Experts believe the prints may have been left by herbivorous prosauropods, which were about ten metres long, had long necks and small heads, weighed up to four tonnes and travelled in packs.

Carabinieri officer Giacomo Regazzoni and park employee Elia Vitalini inspect Late Triassic prosauropod footprints in the Fraele Valley, Italy.

ELIO DELLA FERRARA/STELVIO NATIONAL PARK/AP

The footprints were made about 210 million years ago in soft mud when the Alpine area was a tropical zone and later covered by sediment, which protected the prints, before the mud hardened to become rock.

Fabio Massimo Petti, an ichnologist — a specialist in trace fossils — at the Muse science museum in Trento in northern Italy, said: “The plasticity of those very fine calcareous muds, now transformed into rock, has in areas preserved truly remarkable anatomical details, such as impressions of the toes and even the claws.”

Late Triassic prosauropod footprints on the slopes of the Fraeel Valley in northern Italy.

The footprints appear to ascend the mountain

ELIO DELLA FERRERA/STELVIO NATIONAL PARK/AP

As the Alps were formed, the rock was compressed into a near-vertical position and now stands at 2,000m, far from any path, meaning drones will be needed to study the prints. Fontana said the prints “extend for hundreds of metres and also represent a series of animal behaviours, because in addition to seeing animals walking together, there are also places where these animals meet”.

Cristiano Dal Sasso, a palaeontologist from the Natural History Museum in Milan, said: “The parallel walks are clear evidence of herds moving in synchrony, and there are also traces of more complex behaviours, such as groups of animals gathered in a circle, perhaps for defence.”

Commenting on the approaching start of the Winter Olympics, the Italian culture ministry said: “It’s as if history itself wanted to pay homage to the greatest global sporting event, combining past and present in a symbolic passing of the baton between nature and sport.”