Past degradation of the footprint fossils of dinosaurs in the Oyama district in Toyama City is discussed by constructing and comparing the past 3D shapes of the fossils. The 3D shapes of the fossils that appeared in different times in the past were estimated based on the replicas made by taking a mold in the past and the old photographs taken from various directions in different occasions in the past. The change in the degradation rate in the past was argued by comparing the established 3D shapes in the past. As a result, it was established in the present study that soon after the original outcrop was found by a road construction, a sauropod footprint located in this outcrop started to degrade, but that the rate is getting smaller as time passes. On the other hand, the degradation of the ornithopod footprint, newly found on the one-step lower outcrop in an additional excavation, seems to be getting larger. This study, an examination of the tendency of the degradation fluctuation in the past, will contribute to the discussion of how to conserve such fossils.
