Photo/The Cover

March 9 (NBD) -- A recent discovery in Pengzhou, Chengdu, may confirm that Chengdu was a delta plain or swamp inhabited by primitive turtles 200 million years ago.

On March 7, researchers from China University of Geosciences (Beijing) and their collaborators from the University of Queensland and the Mace Brown Museum of Natural History published their findings in the international academic journal Historical Biology. They described a suspected turtle swimming trace from the Xujiahe Formation of the Upper Triassic in Pengzhou.

In February 13, 2022, several fossil enthusiasts from Chengdu began their “treasure hunt” near a small road in Pengzhou. They had previously collected many plant fossils such as ferns and cycads. At around 11 am, Yong Jun saw something resembling an animal claw print on a gray-black siltstone layer, which is about one square meter in size. He guessed it might be the legendary “chicken footprint” fossil.

The “chicken footprint” has a special place in Sichuan Basin’s fossil record and is usually left by prehistoric carnivorous theropod dinosaurs. Gao Xiang and Zhou Kaisheng came to take a closer look and it really did look like it. The three toes were parallel with the middle one being the clearest and the other two being vaguer.

Xing Lida’s research group at China University of Geosciences (Beijing) later conducted detailed research on this footprint fossil. The footprint is about 7 cm long and 6 cm wide with an obvious three-toed shape and sharp claws at the distal end. Researchers performed a three-dimensional scan and compared it with other reptile footprints.

According to Xing Lida, Yong Jun's isolated footprint is similar to Galapagos footprints found at Xinjiang Urho footprint site and Upper Triassic turtle swimming traces in Spain. The specimen is likely to be a member of the primitive turtle family. But due to too few specimens, scholars cannot completely rule out its connection with crocodiles, theropod dinosaurs or other archosaurs.

The discovery enriches Pengzhou’s Late Triassic animal population indicating potential for discovering more vertebrate fossils records while also helping further infer ancient environments.