A China-U.S. science expedition recently discovered a number of rare, three-dimensional dinosaur footprints while investigating and researching dinosaur footprints in Lianhuabao Village, southwest China's Chongqing Municipality.

Experts with the team said the discovery will help in the understanding of how dinosaurs walked.

The footprints, which were discovered in 2003, are the largest from the cretaceous period. There are more than 300 dinosaur footprints, including concave and convex ones, distributed in an area of 140 square meters and they belong to the Ankylosaurus, Anatosaurus and Theropoda.

During their research, the experts found that some well-preserved convex dinosaur footprints have three toes, with mound-shaped metatarsal prints at the heel and a hoof-shaped claw prints at each toe. The footprints are a half-meter long. The study shows that these footprints are really 3-D dinosaur footprints that belong to the Hadrosaurus.

Xing Lida, an expert with the science expedition, explained that "there probably was a mud pit where the 3-D dinosaur footprints were found."

"When the Hadrosaurus walked there, it left traces," he added. "Afterwards, the pit was filled and formed a mold. Then, we found the interesting footprints."

"We can even clearly see the change of the Hadrosaurus' toes, from splaying to closing together," he said.