The Cretaceous Pierre Shale Group in eastern South Dakota and western Wyoming contains numerous fossils, including the flying reptile Pteranodon, 19 specimens of which are described herein. Pteranodon specimens have been found in the two lower formations of the Pierre Shale Group: 4 in the basal Gammon Ferruginous Formation, and 15 in the overlying Sharon Springs Formation. Of these specimens, 64% are associated forelimb elements. Two factors, or a combination thereof, explain the abundance of associated forelimb elements: (1) predatory preference of the muscle mass in the chest over the wing membrane, which may not have offered much nutrient...