New dinosaur tracks from the Lower Cretaceous (Valanginian-Hauterivian) Saniri Formation of Yeongdong area, central Korea: Implications for quadrupedal ornithopod locomotion

Abstract

Newly discovered tracks of a large quadrupedal ornithopod and a theropod with trail trace, and a bird track from the Cretaceous Saniri Formation of Yeongdong area are described. One ornithopod trackway is very unusual in having large (length width ∼15 and >15 cm respectively) clover-leaf-like manus tracks situated anteromedial to the pes tracks with atypical negative, inward rotation of 45°. Ornithopod pes tracks are quadripartite with three separated, elongate-oval, nearly parallel sided, wide digit impressions and a separate suboval heel impression (mean length and width about 41 and 36 cm respectively: l/w ratio 1.13). Manus track morphotypes are a clover-leaf-shaped configuration of three digit impressions, representing digits II–IV, in triangular configuration and registered just in front of (anteromedial to) pes track digits II and III. The pes morphotype is typical of Caririchnium, but the manus morphotype is quite distinct from previously described ichnotaxa, thus justifying a new ichnotaxon: Caririchnium yeondongensis ichnosp. nov., probably representing a facultatively-quadrupedal Iguanodon-like trackmaker.Theropod tracks are composed of three tapered pes digit impressions with interdigital angles between digits II and IV 45°. Length and width about 22.8 cm and 15.5 cm, respectively. Pace, stride, and pace angles are about 51 cm, 101 cm, and 170°, respectively. Theropod tracks are characteristically associated with a nearly continuous tail trace, which is up to 360 cm in length, 4.5 to 6 cm in width, and broad “U” shaped in cross section. Expulsion rims and dragging striae occur intermittently. In addition, dinosaur skin impressions, poorly preserved large sauropod tracks, a bird track, invertebrate and plant fossils are found from the lake margin deposits also containing rain drop impressions and desiccation cracks. Dinosaur tracks of the Yeongdong area represent the oldest (Valanginian-Hauterivian) dinosaur tracks of Korea.