This Site in Bolivia Boasts 16,600 Exposed Dinosaur Footprints—The Most Ever Found in One Location

Paleontologists counted the record-setting tracks and uncovered evidence of dinosaurs swimming and dragging their tails along what was a muddy superhighway for the animals millions of years ago

Marta Hill | Freelance contributor

December 11, 2025

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Millions of years ago, dinosaurs hightailed their way across what is now a national park in Bolivia.

Paleontologists have documented a whopping 16,600 three-toed dino footprints and 1,378 swim tracks in Torotoro National Park. The findings, published December 3 in PLOS One, provide clues about how the extinct animals may have moved and behaved more than 66 million years ago, during the Cretaceous Period.

“There’s no place in the world where you have such a big abundance of [exposed dinosaur] footprints,” study co-author Roberto Biaggi, a paleontologist at Loma Linda University, tells Carlos Guerrero and Isabel Debre at the Associated Press. “We have all these world records at this particular site.”

The tracks were left behind by a group of two-legged, mostly carnivorous dinosaurs called theropods that included Tyrannosaurus rex and gave rise to modern birds. To document all the prints, found at the roughly 80,000-square-foot tracksite called Carreras Pampa, Biaggi and his colleagues visited the region over several years. 

The printmakers journeyed across what was once deep, soft mud, “which can often end up recording a lot about how these animals moved their feet,” Peter Falkingham, a paleobiologist at Liverpool John Moores University in England who was not involved in the study, tells CNN’s Mindy Weisberger. 

Thanks to the variety of tracks, researchers estimated many of the trackmakers’ sizes, gaits, speeds and other behaviors. For instance, the tiniest footprints were about 4 inches long, and they may have been made by younger animals or smaller species, such as Coelophysis, which weighed around 60 pounds. The largest tracks were roughly 12 inches in length, which could’ve come from mid-size dinosaurs like Dilophosaurus or Allosaurus, weighing in around 900 pounds and 6,000 pounds, respectively.

The swim tracks, on the other hand, are straight or comma-shaped dips typically next to one or two smaller grooves, study co-author Jeremy McLarty, a paleontologist at Southwestern Adventist University, tells Live Science’s Sascha Pare in an email. Some other impressions in the hardened mud came from dinos dragging their tails.

“A skeleton shows what an animal could do; trackways show what it actually did, moment to moment,” Anthony Romilio, a paleontologist at the University of Queensland in Australia who was not involved in the research, tells CNN in an email. “They record speed, direction, turning behavior, slipping, posture and sometimes group movement.”

While the tracks offer a lot of information about the lives of these dinosaurs, they don’t answer why the animals frequented this location.

“It may have been that they were all regular visitors to a large, ancient, freshwater lake, frequenting its expansive muddy shoreline,” Romilio says to AP. Biaggi tells the outlet that the creatures could’ve been fleeing from something or looking for a new home base.

All the tracks were found in one sediment layer, indicating they were made around the same time. That, combined with the numbers and patterns of the tracks, suggests that the dinosaurs didn’t settle in the area. Rather, they were traversing an ancient coastal superhighway.

“Tracks don’t move,” McLarty tells CNN. “When you visit Carreras Pampas, you know you are standing where a dinosaur walked.”

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Marta Hill is a science journalist based in New York City and a former intern at Smithsonian magazine. She is a part of the 2025 class of New York University’s Science, Health and Environmental Reporting Program. Her work has appeared in the Transmitter, Eos, Boston.com and more.