First trackway evidence of gregarious dinosaurs from the Lower Cretaceous Tetori Group of eastern Toyama prefecture, central Japan

Early Cretaceous slender-toed bipedal dinosaur tracks are reported from the eastern part of the Tetori area, central Japan. They are small, bipedal and tridactyl impressions assigned toToyamasauripus masuiaeichnogen. and ichnosp. nov. based on biometric analysis. Thirty-three individuals ofToyamasauripus masuiaeshow the highest density of footprints of any dinosaur track-sites in Japan. This is also the first trackway evidence of gregarious dinosaurs reported from Japan.Toyamasauripus masuiaeappears to represent a small bipedal dinosaur track-maker that was relatively abundant. As no bones are known from the track-bearing beds, the footprints add much to our knowledge of dinosaur faunas at this time.