In Torotoro National Park on the eastern slope of the Andes, Bolivian and American paleontologists have discovered a record-breaking tracksite: nearly 18,000 dinosaur footprints preserved on the surface of an ancient lakeshore. It is the richest footprint locality in the history of paleontology. The findings were published in PLOS One.

16,600 Three-Toed Tracks and 1,400 “Floating” Ones

The study, led by Raul Esperante of the Institute of Geosciences, identified 16,600 footprints belonging to predatory theropods, grouped into 1,300 trackways, along with about 1,400 impressions left by animals that were swimming. All the tracks date to the late Cretaceous period, around 70 million years ago, shortly before the dinosaurs went extinct.

Footprint sizes range from 10 cm (small juveniles) to over 30 cm (adults roughly human-sized). Among them are clear claw grooves, tail marks, and characteristic scratches left by swimming theropods whose feet lightly touched the lake bottom.

Why the Tracks Were Preserved Perfectly

Seventy million years ago, the site was a shallow freshwater lake with a sticky, carbonate-rich floor. Footprints were quickly buried by sediment and fossilized. The rock was composed of two-thirds rounded grains of calcium carbonate and ostracod shells, with the remainder being thin silicate particles. This combination turned out to be ideal: soft enough to capture deep impressions yet strong enough to preserve them until the sediment fully lithified.

Ancient Predator Behavior in High Resolution

The trackways show that theropods regularly walked along the lakeshore, likely searching for water and prey. The researchers identified eleven types of footprints, including sharp turns made while running and smooth trajectories left by swimming animals. It is an exceptionally rare case in which scientists can quite literally “read” the everyday behavior of dinosaurs.

In Brief

A site in Bolivia has yielded the largest collection of dinosaur tracks ever discovered: nearly 18,000 footprints made by theropods 70 million years ago on an ancient lake margin. The extraordinary preservation captured not only walking but also swimming, hunting, and abrupt turns. Carreras-Pampa in Torotoro National Park is now officially the richest “dinosaur footprint cemetery” on the planet.