Tridactyl dinosaur footprints from the Morrison Formation (Upper Jurassic) of northeast Wyoming

Discovery of a second footprint locality in the Morrison Formation of the Black Hills provides evidence for the presence of relatively small theropod and/or ornithopod dinosaurs. The footprints occur at the top of a channel sandstone overlain by bone‐rich siltstones. The footprints are notably smaller than those previously reported from the Black Hills by O. C. Marsh and appear to be different from any reported hitherto from the Morrison Formation. The relatively common occurrence of small tridactyl footprints in the Morrison Formation indicates that small bipedal dinosaurs may have been more common in North America during the Late Jurassic than is apparent from the skeletal record.

Key words:

• dinosaur tracks
• Morrison Formation
• Jurassic
• theropod
• ornithopod