TRACKING 16,600 DINOSAUR FOOTPRINTS

Step by step, paleontologists study impressions left more than 60 million years ago by T. Rex and other theropods

- CARLOS GUERRERO AND ISABEL DEBRE

RANGER Jose Vallejos stands next to dinosaur footprints in Toro Toro National Park in Bolivia.

JUAN KARITA Associated Press

Legend once had it that the huge, three-toed footprints scattered across the central highlands of Bolivia came from supernaturally strong monsters - capable of sinking their claws even into solid stone.

Then scientists came here in the 1960s and dispelled children's fears, determining that the strange footprints in fact belonged to gigantic, two-legged dinosaurs that stomped and splashed over 60 million years ago, in the ancient waterways of what is now Toro Toro, a village and popular national park in the Bolivian Andes.

Now, a team of paleontologists, mostly from California's Loma Linda University, have discovered and meticulously documented 16,600 such footprints left by theropods, the dinosaur group that includes the Tyrannosaurus rex. Their study, based on six years of regular field visits and published Dec. 3 in the peer-reviewed journal PLOS One, reports that this finding represents the highest number of theropod footprints recorded anywhere in the world.

"There's no place in the world where you have such a big abundance of [theropod] footprints," said Roberto Biaggi, a coauthor of the study led by Spanish paleontologist Raúl Esperante. "We have all these world records at this particular site."