This undated photo provided by Xing Lida,吃瓜是什么意思? an associate professor at the China University of Geosciences Beijing, shows a fossilized footprint found in Wulan Town of Jingyuan County, northwest China's Gansu Province. (Xinhua)

by Xinhua writer Yuan Quan

BEIJING, Jan. 7 (Xinhua) -- Scientists have confirmed that a group of fossilized tracks found in northwest China were left by flesh-eating dinosaurs over 120 million years ago, providing insights into the social behaviors of these ancient creatures.

The track site is located in Wulan Town of Jingyuan County, Gansu Province. Scientists discovered at least 67 three-toed tracks on a cliff at the base of a 6.2-square-meter sandstone, which is approximately the height of an adult man.

The lengths of these tracks range from 11 cm to 21 cm, and none include the first toe or tail marks.

Considering the lengths and shapes of the tracks, scientists estimated that the creatures had a hip height between 60 cm and 90 cm, with the largest one having a body length of up to 2.5 meters, while these creatures moved in a nearly straight line.

After a detailed examination, scientists identified these tracks as belonging to Grallator ssatoi -- which were made by a carnivorous dinosaur that roamed the Earth during the Cretaceous period.

The study results were recently published online in the international journal Historical Biology.

According to the study, the area where the track site is located was submerged by the Yellow River until a few decades ago. In the 1970s, as rock walls were blasted and roads constructed, these tracks were likely exposed. A resident recalled discovering these unusual footprints in 2006 when she was just 13 years old. Recognizing their potential significance as dinosaur tracks, she reported her findings to the local cultural relics bureau in 2020. In June 2023, researchers had the opportunity to examine the track site.

The track site is situated about 100 km east of the Lower Cretaceous Hekou Group, an area renowned for having one of the highest diversities of Cretaceous four-footed tracks in China. To date, 31 Lower Cretaceous tetrapod footprint sites have been recorded there, featuring over 1,000 dinosaur tracks, including a wide variety of three-toed theropod footprints, such as those belonging to Grallator, Eubrontes and Asianopodus.

Such dense tracks can also offer insights into the behavior of the creatures who made the tracks.

According to lead author Xing Lida, associate professor at the China University of Geosciences Beijing, previous studies have shown that some groups of small biped dinosaurs had demonstrated gregarious behavior.

In the new study, scientists discovered 12 similar-sized tracks. Some of them run parallel to each other, moving in the same direction -- which indicates that these species might have exhibited social behavior. "Such behavior could have been a strategy for small dinosaurs to protect themselves from predators," said Xing. "By staying close to one another, they may have reduced the pressure on each individual to remain vigilant."

The dinosaur expert also noted some "surprises" produced by the study.

"Some of the tracks feature lateral drag marks, which suggest that while walking, the dinosaurs may have slipped sideways but were able to regain their balance promptly," Xing told Xinhua.

These well-preserved footprints offer new scientific evidence concerning the distribution of dinosaurs in China and provide clues that can help scholars gain a deeper understanding of dinosaur footprints and behaviors.

The reconstructed tracks hold significant scientific and educational value, Xing added, "They are much like a prehistoric documentary, bringing to life the world of dinosaurs during the Cretaceous period."

This image provided by Xing Lida, an associate professor at the China University of Geosciences Beijing, shows a depiction of dinosaurs based on the fossilized tracks they had left. (Xinhua)