TORO TORO, Bolivia, Dec 9, (AP): 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 last Wednesday 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 co-author of the study led by Spanish paleontologist Raúl Esperante. "We have all these world records at this particular site.” The dinosaurs that ruled the earth and roamed this region also made awkward attempts to swim here, according to the study, scratching at what was squishy lake-bottom sediment to leave another 1,378 traces.

They pressed their claws into the mud just before water levels rose and sealed their tracks, protecting them from centuries of erosion, scientists said. "The preservation of many of the tracks is excellent,” said Richard Butler, a paleontologist at the University of Birmingham who was not involved in the research. He said that, to his knowledge, the number of footprints and trackways found in Toro Toro had no precedent.

"This is a remarkable window into the lives and behaviors of dinosaurs at the end of the Cretaceous,” Butler added, referring to the period around 66 million years ago at the end of which an asteroid impact abruptly extinguished all dinosaurs and 75% of living species along with them, according to scientists. Although they've survived for millions of years, human life has threatened these traces.

For decades, farmers threshed corn and wheat on the footprint-covered plateaus. Nearby quarry workers didn’t think much of the formations as they blasted rock layers for limestone. And just two years ago, researchers said, highway crews tunneling through hillsides nearly wiped out a major site of dinosaur tracks before the national park intervened.