Bold claim: a single Bolivian plateau now stands as the world’s richest snapshot of dinosaur life, with thousands of footprints revealing how these ancient animals moved, played, and struggled in at least one coastal mudflat 60 million years ago. And this is where it gets controversial: what these tracks say about dinosaur behavior challenges long-held assumptions about their lives before the mass extinction.
Scientists have long known that central Bolivia’s Toro Toro region holds a remarkable fossil footprint record. In the 1960s, researchers clarified that the strange three-toed impressions belonged to gigantic two-legged dinosaurs that roamed and splashed through ancient waterways long before our time. Recently, a team led by Raúl Esperante and including several researchers from California’s Loma Linda University documented 16,600 theropod footprints—footprints left by the group that includes predators such as the Tyrannosaurus rex. Their six-year field effort and the resulting study in PLOS One mark the largest collection of theropod trackways ever recorded.
There’s no other place on Earth with so many theropod footprints all in one place, noted co-author Roberto Biaggi. The site offers a comprehensive record of dinosaur life during that era, and the researchers describe Toro Toro as a global benchmark for theropod traces.
The team didn’t just catalog footprints; they also identified 1,378 additional tracks left when dinosaurs attempted to swim or wade through soft, lake-bottom sediments. These marks were made just as water levels rose, helping to preserve them by burying them in mud and protecting them from erosion over centuries.
Experts unaffiliated with the study praised the preservation quality and the sheer abundance of tracks. Richard Butler, a paleontologist at the University of Birmingham, called this discovery a remarkable window into dinosaur lives at the end of the Cretaceous period, roughly 66 million years ago, when an asteroid impact ended the age of dinosaurs and drove a mass extinction.
Human activity has repeatedly threatened Toro Toro’s track record. For years, farmers and quarry workers disturbed the surface—threshing, blasting, and tunneling—putting important traces at risk. A recent example involved highway work that nearly erased a major track site before the national park intervened. The consequences of such disturbances may partly explain why bone remains are surprisingly rare in the area, despite the abundance of footprints and swim traces.
The absence of bones does not necessarily reflect a simple ecological story. The scientists suggest that most tracks come from walking along a broad, ancient coastal pathway that stretched from southern Peru into northwest Argentina, with the variety of footprint sizes indicating a herd that included enormous giants and much smaller theropods roughly the size of a chicken.
From footprints alone, researchers can infer behavior—when dinosaurs walked, ran, paused, or turned—offering insights that skeletons alone cannot provide. One possibility is that the herd moved together along a vast muddy shoreline near a freshwater lake, while another possibility is that many individuals were drawn to this route by resources or safety.
Despite the robust findings, questions remain about why such a spectacular congregation of theropod tracks occurred at Toro Toro and what kept attracting them to this area over time. Biaggi suggests that the site might continue to yield new discoveries for years to come, as researchers expand around the edges of the currently uncovered sections.
What this study clearly demonstrates is that the Toro Toro tracksite is a priceless archive of dinosaur behavior—potentially reshaping our understanding of how theropods lived, moved, and organized socially just before the end-Cretaceous extinction. Do these tracks indicate a coordinated herd migration, or simply a favored route for opportunistic travelers? How should preservation priorities be balanced with ongoing exploration to ensure future discoveries? Share your take in the comments: does this change how you picture dinosaur life, or do you still favor alternative explanations?
De tedious reporting from Buenos Aires, Argentina.
