Evidence for a mixed-age group in a pterosaur footprint assemblage from the early Upper Cretaceous of Korea

Here we describe a new pterosaur footprint assemblage from the Hwasun Seoyuri tracksite in the Upper Cretaceous Jangdong Formation of the Neungju Basin in Korea. The assemblage consists of many randomly oriented prints in remarkably high densities but represents a single ichnotaxon, Pteraichnus. Individuals exhibit a large but continuous size range, some of which, with a wingspan estimated at 0.5 m, are among the smallest pterosaurs yet reported from the Upper Cretaceous, adding to other recent finds which contradict the idea that large and giant forms entirely dominated this interval. Unusual features of the tracks, including relatively long, slender pedal digit impressions, do not match the pes of any known Cretaceous pterosaur, suggesting that the trackmakers are as yet unknown from the body fossil record. The Hwasun pterosaur footprints appear to record gregarious behavior at the exact location by individuals of different ages, hinting at the possibility that pterosaurs gathered in mixed-age groups.

Automated summary

This study describes a new pterosaur footprint assemblage discovered in the Upper Cretaceous Jangdong Formation of the Neungju Basin in Korea. The assemblage contains randomly oriented prints of the same ichnotaxon, Pteraichnus, with high densities. Some of the individuals have a wingspan estimated at 0.5 m, making them among the smallest pterosaurs known from the Upper Cretaceous. The footprints exhibit unusual features that do not match any known Cretaceous pterosaur, suggesting the possibility of an undiscovered species. The presence of footprints from individuals of different ages at the same location hints at gregarious behavior in pterosaurs.