Dinosaur egg fossils found in Dadaepo, Busan, have been confirmed as evidence that large oviraptorosaurs lived on the Korean Peninsula in the early Late Cretaceous. The findings also suggest that the Dadaepo area, now a seaside, may then have been a dry climate with lakes and rivers, and an environment with active volcanic and seismic activity.
A research team led by Choi Seung of Seoul National University and Baek In-seong of Pukyong National University announced an analysis of dinosaur eggs discovered in Dadaepo, Busan, in the 2010s. The results were published on the 20th in the international journal Papers in Palaeontology.
Dinosaur eggs are records that show which dinosaurs bred where, whether the surrounding environment was dry or wet, and at times even the physiological state of the egg-laying dinosaur. The team examined the microstructure, chemical composition, and degree of thermal metamorphism of the dinosaur eggs discovered by Professor Baek In-seong in the 2010s.
Lead researcher Choi Seung told ChosunBiz, "The Dadaepo dinosaur eggs appear to have been influenced by Cretaceous geothermal heat exceeding 300 degrees for a long time, but their microstructure was well preserved," adding, "We made broad use of the most advanced techniques currently applicable to dinosaur egg research."
As a result, at least two types of dinosaur eggs were mixed in the Dadaepo egg fossils. One is Mosaicoolithus, which has also been reported in Zhejiang and Henan in China; the other is Macroelongatoolithus, found in China, Mongolia, Korea, the United States, and elsewhere.
Of these, Macroelongatoolithus is well known from previous studies as the eggs of large oviraptorosaurs. This is strong evidence that large oviraptorosaurs lived in the Dadaepo area of Busan. Oviraptorosaurs are a group of theropod dinosaurs close to birds, likely had feathers, and some species left traces of sitting on nests to brood their eggs.
In particular, the fossil site where the egg fossils were found had been interpreted as belonging to the relatively younger late stage of the Late Cretaceous. Similar dinosaur egg fossils had previously been reported in Aphaedo, South Jeolla, and Goseong, South Gyeongsang. Some paleontology experts therefore interpreted that "large oviraptorosaurs may have survived longer in Korea than in other regions." However, this study revealed that oviraptorosaurs existed on the Korean Peninsula from the early Late Cretaceous.
Choi said, "Looking at oviraptorosaurs as a whole, many interpretations have suggested dinosaurs moved from Asia to North America, but in the case of large oviraptorosaurs, the North American specimens are slightly older in age, raising the possibility that they appeared first in North America and then spread to Asia via the Bering Strait."
By analyzing traces that the egg fossils were affected by geothermal heat, the team also inferred that Busan at the time would have looked entirely different from today. The Dadaepo area may have had lakes and rivers flowing in a dry climate, and seismic and volcanic activity could have been quite active, more so than in today's Kyushu volcanic region of Japan.
Researcher Choi Seung added, "This study shows that regional fossils in Korea can provide clues to solve important questions in paleontology," and "Our goal is to analyze eggs on the Korean Peninsula that were thought to be poorly preserved due to significant heating and to establish benchmarks for dinosaur egg research."
References
Papers in Palaeontology (2026), DOI: https://doi.org/10.1002/spp2.70084