Scientists at the University of Arkansas, Fayetteville, said the field in southwest Arkansas covers an area of about two football fields and contains the fossilized tracks of several species.
Some tracks are from species never previously documented in Arkansas, a university release said Wednesday.
"The quality of the tracks and the length of the trackways make this an important site," researcher Stephen K. Boss said, noting that the rock types where the footprints were found provide clues to what the climate would have been like 120 million years ago.
"Picture an environment much like that of the shores of the Persian Gulf today. The air temperature was hot. The water was shallow and very salty," Boss said. "It was a harsh environment. We're not sure what the animals were doing here, but clearly they were here in some abundance."
The most dramatic tracks, about 2 feet long by a foot wide, may have been those of a three-toed Acrocanthosaurus atokensis, one of the largest predators ever to walk the earth, the researchers said.
Tradition tools such as hand-held brooms and plaster to make casts are being used alongside cutting-edge instruments such as laser scanners to study the tracks, the scientists said.