Ancient Anatomy (IMAGE) Brown University Caption How do we know Bunostegos walked upright on all fours? The bones in four areas: 1) the shoulder 2) the humerus 3) the elbow joint 4) the radius and ulna. Credit Image: Morgan Turner Usage Restrictions with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.