Only about 50 dinosaur tail-drag traces have ever been reported worldwide, across nine countries. As of Tuesday, South Korea officially has one it can still show you — on a riverbank in Ulsan, an industrial city better known for building cars and ships than for 100-million-year-old reptiles.
On November 3, the Ulsan Metropolitan Government held a briefing at the Ipam-ri fossil site in Ulju-gun, on the banks of the Taehwa River, to announce the final results of a six-month study that began in May. The research was carried out by the Industry-Academia Cooperation Foundation of the Korea National University of Cultural Heritage and led by Professor Gong Dal-yong. Its headline finding: a roughly 8.2-meter quadrupedal sauropod trackway with a continuous drag mark running down its center, left by a tail. It is, the researchers say, the only preserved dinosaur tail-drag trace in the country.
Why a tail mark matters more than a footprint
A tail trace is a different kind of fossil from a footprint. It records behavior rather than anatomy, and it needs an unusual set of conditions to form and survive. Korea’s first such trace was reported in 2011 in Yeongdong, North Chungcheong Province, but that site was destroyed in a slope collapse. Ipam-ri is now the only place in the country where one survives.
The Ulsan trackway also tells a small story about how the animal was moving. The forefoot prints are much smaller and shallower than the hind prints, which is not how a sauropod normally walks on dry ground. The team’s interpretation is that the dinosaur was wading through water deep enough to partly float its body, shifting its weight back onto its hind legs and letting the tail sag until it scraped the lake bed.
A second trackway in another zone of the site belongs to Caririchnium, a footprint type associated with large ornithopods (two- and four-legged plant-eaters). From the spacing of the prints, the researchers estimate the animal’s hip height at about 1.16 meters and its pace at roughly 2.3 km/h — a stroll, not a run.
A lakeshore under a riverbank
The Taehwa River today runs through the middle of Ulsan. About 100 million years ago, during the Cretaceous, the Ipam-ri area was the edge of a lake. The sediment preserves ripple marks, raindrop impressions, polygonal mud cracks and ancient soil layers, which together point to a shoreline that flooded in the wet season and dried out in the dry season. Microbial mats on the surface are thought to have helped the footprints set before they could be washed away.
Footprints appear on at least seven separate rock horizons, meaning dinosaurs returned to this spot repeatedly over a long period rather than passing through once. The total count of confirmed dinosaur footprints at the site now stands at 15.
The site has had a quiet history. The Cultural Heritage Administration (now the Korea Heritage Service) first confirmed two or three footprints and a possible tail mark during a 2012 survey, but could not prove what the mark was. River maintenance work in 2023 exposed more prints; the city, judging the exposed rock at risk, covered it with clay to protect it. In 2025 Ulsan named the location a candidate geosite in its application for national geopark status. The new study used 3D scanning and drone photogrammetry to document the trackways in detail, and it finally confirmed the 2012 mark as a genuine tail-drag trace.
What happens next
Ulsan says it will push to upgrade the site from candidate to formal geosite within the national geopark system and to seek designation as a Natural Monument, the national designation for protected natural heritage. The study also recommends protective viewing structures and safe visitor routes, carefully removing overlying sediment under expert supervision to look for more fossils, and building a geotrail that would link Ipam-ri with nearby sites including Seonbawi Rock, the Guksucheon fold, and the Cheonjeon-ri, Daegok-ri and Bangucheon petroglyphs, prehistoric rock carvings a short distance away.
For a city whose name is usually followed by the words “shipyard” or “refinery,” a dinosaur that went for a wade 100 million years ago is a welcome change of subject.