Scientists in Bolivia have discovered the largest collection of dinosaur prints ever found, with the tracks documenting the animals’ attempts to swim.

Over 16,000 immaculately-preserved theropod prints — the family of dinosaurs that includes the Tyrannosaurus rex — were uncovered in ancient waterways in Toro Toro, a national park in the Bolivian Andes.

The tracks were left by dinosaurs attempting to swim through lakes in the area, leaving their footprints in the mud. As the tracks were made before water levels rose, they were protected from erosion, according to scientists.

Park Ranger Celso Aguilar described the discovery as the “most important finding in the world that can be observed”.