First report of bird tracks (Ignotornis seoungjoseoi ichnosp. nov.) from the Jinju Formation (Lower Cretaceous), Sacheon City, Korea

Abstract

This is the first report of the webbed bird tracks from the middle part of the Jinju Formation (Lower Cretaceous: upper Aptian–lower Albian) in Bito Island, Seopo-myeon, Sacheon City, Gyeongnam, South Korea. Although it is well known that the avian tracks are very abundant and diverse in the Cretaceous Hayang and Yucheon groups of the Gyeongsang Supergroup, bird tracks of the Sindong Group have never been reported. The bird tracks, which are comparatively small (about 3.5 cm length excluding hallux), tetradactyl with a functional reversed hallux, asymmetric and semi-palmate webbing in the hypex between digits II–III and III–IV and are characterized by narrow divarication angle (about 79.8°) between digits II and IV, are described herein as a new ichnotaxon, Ignotornis seoungjoseoi ichnosp. nov. Left and right footprints set showing standing traces is well preserved on the track surface. Tracks of Jindongornipes ichnosp. were also recovered from the intertidal zone of Bito Island, and is the first report of this ichnogenus from the Jinju Formation on Bito Island. The discovery of two ichnotaxa of bird tracks from the Jinju Formation demonstrates that bird diversity from the Lower Cretaceous (upper Aptian–lower Albian) to Upper Cretaceous (Maastrichtian) track record, and the record of terrestrial vertebrate diversity from the Cretaceous Period of Korea, is still in the process of being fully documented and understood.