Several species, including the eight-ton Acrocanthosaurus atokensis—one of the largest predators ever to walk Earth—and sauropods, or long-necked plant-eaters, left their footprints in the 120-million-year-old Cretaceous limestone.

At the time, Arkansas was a broad mud flat, similar to the hot, dry, and salty shores of the modern-day Persian Gulf—not a particularly "pleasant place," said team leader Stephen Boss, a geoscientist at the University of Arkansas in Fayetteville.

Predators like Acrocanthosaurus were likely attracted to the site by sauropods and other prey species, but "what the sauropods are doing out there, who knows?" Boss said.

"They don't think this is a place that dinosaurs once roamed, but it is—and here's the proof."

(See "First Dinosaur Tracks Found on Arabian Peninsula.")

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