A Reexamination of Dinosaur Trackmakers Based on Three-Dimensional Quantitative Data from the Lower Cretaceous Tetori Group of the Oshirakawa Area, Gifu Prefecture (Japan)

Abstract

Researchers disagree on the identity of dinosaurs that left footprints in the Lower Cretaceous Tetori Group of the Oshirakawa area (Japan). To clarify these identities, we quantitatively analyzed footprint data obtained from three-dimensional laser scanning technology. From these data, we identified six tracks belonging to dinosaurs. These six tracks were bipedal with a tridactyl morphology, which we could differentiate into large theropods (the ichnofamily Eubrontidae) and large ornithopods (similar to Amblydactylus-type). Our results indicate that the ichnofauna of the Oshirakawa site is richer than previously thought. Additionally, the cooccurrence of large theropod and Amblydactylus-type ornithopod footprints in the Oshirakawa area is the oldest in the Tetori Group (although a similar assemblage was identified in the Kitadani Formation, which is the uppermost part of the Tetori Group). Thus, quantitatively assessing dinosaur footprints using 3D digital data is an effective approach to identify dinosaur footprints.