First report on Trackways of Mesozoic aquatic reptile, Choristodera from Korea
- discovered during the excavation around UljuBangudaePetroglyps in 2018/ new ichnospecies, Novapesulsanensis, named-
National Research Institute of Cultural Heritage, Cultural Heritage Administration (CHA), reported new fossils of four-legged vertebrate footprints today after an academic survey and excavation* around the BangudaePetroglyps (national treasure # 285) in Daegok-ri, Ulju-gun in 2018. The result was published in a sister magazine of Nature, Scientific Reports.
*Refer to the press release on June 5, 2018, ``Discovery of new fossils of four-legged vertebrate footprints around the UljuBangudae Petroglyphs'’
At the time of discovery, the fossils received a lot of attention from the academic societies and the public because they were identified as a completely different type of footprints from those reported previously in Korea (dinosaurs, pterosaurs, turtles, crocodiles, lizards, and other mammals' footprints).
The fossils turned out the footprints of an aquatic reptile, Choristodera,that appeared in the Mesozoic (Middle Jurassic) and became extinct in the Cenozoic (early Miocene)*. This is the first finding in Asia and the second in the world.
Choristodera's footprint fossils were first reported in the United States in 1995 with only two incomplete footprints. Therefore, this new trackway (consisting of nine manus and nine pes) found around the Ulsan Bangudae petroglyphs is not only the world's first complete choristoderan trackway but also the only direct evidence for understanding the walking pattern and behavior of Choristodera which were not known until now.
* Middle Jurassic of the Mesozoic Era (about 174 million years ago) ~ Early Miocene of the Cenozoic Era (about 16 million years ago)
The newly discovered choristoderan footprints were named “Novapesulsanensis” after the area of Ulsan where the fossil was found, which means “a new footprint found in Ulsan”.
A choristoderan that left Novapesulsanensiswas estimated to be about 90 to 100 cm long. It had five digits in both hands and feet with a long tail. The webbing in pes prints strongly supports that Choristodera was well adapted to the water. In addition, it was confirmed for the first time that some choristoderanswalked in a semi-upright gait like a crocodile, unlike dinosaurs and lizards. Novapesulsanensisis considered to have been formed by a choristoderan similar to Monjurosuchusbecause it is well-matched with the foot’s skeletal features of Monjurosuchusreported from the Early Cretaceous strata of China.
This research demonstrates that, during the Mesozoic in Korea, an aquatic reptile “Choristodera” inhabited along with diverse vertebrates including dinosaurs, pterosaurs, birds, lizards, crocodiles, turtles, and mammals. This discovery confirms that the area of the “Bangudae Petroglyphs in Daegok-ri, Ulju” is an important heritage area because it has world-class natural heritage such as dinosaurs and birds coexisted with aquatic reptiles based on their footprints during the Cretaceous as well as cultural heritage of outstanding value, Bangudae Petroglyphs.
The National Research Institute of Cultural Heritage of CHA will continue to research on natural heritage in the area of “Bangudae Petroglyphs in Daegok-ri, Ulju,” and the results of this research will be released to the public during next year at the Natural Heritage Center exhibition hall.