Oblique ankle joint (IMAGE) University of Bristol Caption The oblique ankle joint did not allow Euparkeria to assume a fully upright posture as the foot also turns medially when the ankle joint is extended. An ankle joint allowing a more upright posture evolved later independent from the hip structure. Credit Oliver Demuth Usage Restrictions None 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.