World’s Largest Dinosaur Footprint Site Discovered in Bolivia’s Toro Toro — 16,600 Theropod Tracks Preserved in Mud

A multinational team of paleontologists, led largely by researchers from Loma Linda University in California, has documented what appears to be the highest concentration of three‑toed dinosaur tracks ever recorded. After six years of fieldwork at nine locations in central Bolivia, researchers catalogued 16,600 theropod footprints — the meat‑eating group that includes well‑known genera such as Tyrannosaurus and other bipedal predators.

Discovery and Scale

The nine mapped locations connect to form a single, extensive prehistoric complex now considered the world’s largest known tracksite. Some imprints may be as old as about 60 million years and appear to record repeated passages of groups or herds of dinosaurs across soft sediments.

“It's the biggest discovery in history. 1,700 fossils and more than 17,000 footprints have been found, and it is very likely that thousands more will be found in the national park,” said Toro Toro park superintendent Celso Aguilar, describing the site’s scale and ongoing potential.

How the Tracks Were Preserved

The study also documents roughly 1,378 trace marks interpreted as swim or claw‑scrape traces. Researchers interpret these as animals digging their claws into squishy lake‑bed sediment just before water levels rose and sealed the impressions, protecting them from centuries of erosion and preserving an extraordinary snapshot of behavior.

Why Bones Are Scarce

Despite the thousands of footprints, Toro Toro has yielded very few bones, teeth or eggs. Part of that absence may reflect human disturbance: quarrying and highway tunneling historically damaged exposures, and early local reactions in the 1960s — when some residents feared the marks were signs of monsters — sometimes led to bones being broken or plowed over.

However, the research team also proposes a natural explanation: the density, alignment and consistent sedimentary layer of the tracks suggest a migratory corridor — an ancient coastal 'superhighway' used by dinosaurs moving between southern Peru and northwest Argentina — rather than a permanent resident population that would leave abundant skeletal remains.

Threats And Conservation

Ongoing threats from quarrying and construction have already put parts of the site at risk; two years ago, highway work nearly destroyed a major concentration of tracks before the national park intervened. The discovery highlights the need for protection, careful documentation and continued fieldwork, which may yet reveal additional tracks and fossils.

Significance: Toro Toro offers an unparalleled window into dinosaur behavior, movement and environment — recording not just individual footprints but large‑scale patterns of travel and interaction across a vast prehistoric landscape.