World’s Largest Dinosaur Tracksite: 16,600 Theropod Footprints Mapped in Bolivia

Massive Dinosaur Freeway Discovered at Carreras Pampas

Paleontologists have mapped an extraordinary concentration of theropod footprints at the Carreras Pampas exposure in Torotoro National Park, Bolivia. Field teams documented 16,600 three-toed, bipedal predator prints preserved in soft mud from about 101 to 66 million years ago, making this the most extensive dinosaur tracksite recorded to date.

Scope, Preservation, and Directionality

The mapped footprint-covered surfaces cover roughly 80,570 square feet (7,485 square meters). While some impressions are isolated, many form continuous trackways — sequences of prints made by the same animal — and most trackways trend north-northwest or southeast. Researchers suggest the shoreline functioned as a high-traffic “dinosaur freeway,” possibly connecting movement corridors across parts of Argentina, Bolivia and Peru.

Behavioral Insights From Tracks

Print shape and stride spacing reveal a variety of behaviors: relaxed walking, rapid running, and more than 1,300 traces interpreted as swimming or buoyed locomotion in shallow water. Several trackways preserve tail drag marks. Estimated hip heights for the trackmakers range from about 26 inches (65 cm) to more than 49 inches (125 cm), indicating a wide range of sizes. The site also produced several hundred bird tracks sharing the same shoreline.

“Everywhere you look on that rock layer at the site, there are dinosaur tracks,” said Dr. Jeremy McLarty, coauthor of the study and director of the Dinosaur Science Museum and Research Center.

Why Tracksites Matter

Unlike isolated bones, trackways capture behavior in place — speed, direction, slipping, posture, and evidence of group or repeated use of a route. As Dr. Anthony Romilio notes, “A skeleton shows what an animal could do; trackways show what it actually did.” Experts also emphasize that deeper impressions can preserve nuanced foot motion, while swimming impressions record when water buoyed the animal, changing how toes contacted the substrate.

Context and Open Questions

Carreras Pampas has been known since the 1980s, but this is the first detailed, site-wide scientific survey, published in PLOS One. The new mapping raises questions about why theropod prints dominate this surface — a contrast with many sites worldwide that preserve abundant sauropod herd traces — and whether the variety of sizes reflects different species, age classes, or both. Before this mapping, the Bolivian site Cal Orck’o (near Sucre) held the largest estimated count at about 14,000 prints.

Significance: This exceptionally dense and well-preserved assemblage offers a rare, moment-in-time view of late Cretaceous shoreline ecosystems and how dinosaurs and birds used them.