A research team composed of Associate Professor Xing Lida and PhD student Chen Qiyan from China University of Geosciences (Beijing), Professor Li Daqing from Gansu Agricultural University, and Director You Wenze of the Dinosaur Museum of the Yellow River Three Gorges Scenic Area Management Committee recently published a new discovery in the international geological academic journal "Cretaceous Research". The research team discovered an important group of ancient animal footprint fossils in the red sandstone of the Lower Cretaceous River Mouth Group in Yongjing County, Linxia Hui Autonomous Prefecture, Gansu Province. This is considered to be China's first turtle trail and the first group of turtle bird symbiotic footprints. Fossil footprints of birds and turtles. It is reported that from 2020 to 2022, You Wenze, director of the Dinosaur Museum of the Yellow River Three Gorges Scenic Area Management Committee, and museum staff Luo Dajun discovered six Early Cretaceous footprints in Honglou Village in Guanshan Township, Kongjiasi Village in Taiji Town, and Liujiaxia Dinosaur National Geopark in Yongjing County. All footprints are preserved in the red sandstone of the Lower Cretaceous estuary group, with bird footprints found at 5 out of 6 footprint points, including one accompanied by turtle footprints. Li Daqing stated that Yongjing is a famous early Cretaceous fossil site in China, where a large number of well preserved important fossils such as dinosaur bones and footprints have been discovered. At the Kongjia Temple footprint site, scholars have discovered small and medium-sized turtle footprints, among which paired front and back footprints can be identified. This is the first accurate ancient turtle trail, and its preservation status and regularity are better than previous discoveries in China. Based on its morphological characteristics, Xing Lida's research team identified it as a turtle footprint genus and inferred that these turtle footprints may have been caused by turtles "walking" along shallow water bottoms, or by swimming in shallow water and occasionally leaving their fins on the bottom of the water. Some of the turtle footprints were clearly covered by bird footprints, indicating that turtle footprints formed before bird footprints. In addition, the length range of the footprints in the newly discovered 5 bird footprint points is 3 to 4 centimeters, which is very similar to the footprints of the Lee's Korean bird previously discovered in the Hekou group. The research team identified the newly discovered footprints as the Korean bird footprint genus, which is a common bird footprint species in the Cretaceous period in China. Xing Lida said that this depicts an ancient ecological scene for people: turtles walk or swim and play in shallow water, leaving footprints. As the water level drops, the area is exposed, and a large number of birds arrive in the area to forage, causing the bird footprints to overlap with the turtle footprints. Scene restoration of lakeside bird and turtle trackers. In addition, the research team found that the size of footprints of Mesozoic turtles is positively correlated with the size of footprints of other quadrupedal animals in the same location. That is to say, if smaller sized turtle footprints are found at the same location, then the footprints of other quadrupedal animals are also relatively small. On the contrary, large-sized turtle footprints are also accompanied by footprints of other large-sized quadrupeds. This indicates that in the riparian environment dominated by dinosaurs in the Mesozoic era, animals of different sizes adapted to different water depths. This provides scientists with a new method for determining and dividing ancient water depths. In addition, this study enriches the early Cretaceous dinosaur fauna in Yongjing and provides new materials for studying the ancient ecology of the region, "said Xing Lida. (New Society)