Scientists have discovered over 4,300 dinosaur footprints in Hebei province of Zhangjiakou in northern China. This is the largest number of footprint fossils found in one spot in the country, according to a report in the South China Morning Post. The footprints were made between the Jurassic and Cretaceous ages, around 150 million years ago. The Indian Express looks at the significance of the discovery, and what dinosaur footprints tell us about the prehistoric amphibians. Dinosaur footprints in China: the discovery and its importance The largest number of dinosaur footprint fossils located in northern China, these cover an area of 9,000 square metres. According to news reports, the footprints show four different dinosaur species, one of which might be undiscovered. The report, published last month in the South China Morning Post, states that the footprints belong to herbivores and carnivores dinosaurs; while the former could reach lengths of nearly 15 metres, the latter was four to five metres. Scientists believe the area may have attracted dinosaurs due to the availability of water and trees at the time. Though announced last month, the discovery was made in 2020, and since then, scientists have been carrying out 3D imaging of the footprints and casting molds of them. How did the dinosaur footprints become fossils? Preserved footprints, also known as ichnites, are trace fossils that have survived millions of years. These are found in earthen materials that were soft enough to form the foot impression and hard enough to retain it. Over time, the material dried, hardened, and was covered with layers of sediment, helping the impression become fossilised. In numerous instances, soil erosion is now bringing them to the surface. While several dinosaur fossils and footprints are believed to have been found in Europe and North America in the 1700s, these were declared to be remains of very large birds or biblical giants. The first dinosaur footprints in the United States were reportedly found in 1800 by Pliny Moody on his farm in Connecticut. About one foot long, scientists at the time identified the prints as that of Noah's Raven, referring to the Bible. In the 1820s, fossil footprints were reported from Cheshire, England, in Triassic rocks. The earliest written record of fossil footprints, these are now referred to as the ichnogenus Chirotherium. Since then, dinosaur footprints have been discovered across the world. In 2017, in the French village of Plagne, scientists uncovered the world’s longest dinosaur tracks, measuring more than 150 metres. It was said to be made by a dinosaur that was at least 35 metres long and weighed 35 tonnes. In India, in 2014, footprints dating back 200-million-years were found in Jaisalmer, Rajasthan. What do dinosaur footprints tell us? Dinosaur tracks denote the activity of an animal when it was alive. In the South China Morning Post report, Michael Pittman, paleontologist at the Chinese University of Hong Kong, says, “Trackway sites tell us about the types of dinosaurs that lived in the original ecosystems, and they can also preserve the tracks of other animals, like lizards and insects. They tell us about the behaviour of the track maker. For example, they tell us how dinosaurs ran and walked, and some seem to record them swimming.” Paleontologists also study dinosaur gait and speed from the footprint tracks. For instance, footprints close together indicate the animals were running, while spaced footprints mean they were walking. While it is difficult to identify the exact species of dinosaur that made a track, trackways do help determine if it was made by a bipedal or quadrupedal dinosaur, which moves on two or four legs, respectively. In instances where the remains are intact, scientists are also able to examine skin impressions of the animals and details of the claw marks.
