Fig. 3. Changes in joint angles during walking at typical speeds (representative trials). Speed and step frequencies are noted in parentheses. The contact angle depicted for Eremopus and Leiobunum is the projection onto the sagittal plane of the angle between the substratum and lever arm and was used to calculate potential propulsive work due to elastic recoil. Dotted lines are inferred due to incomplete kinematic information. The basitarsus—telotarsus joint angle is diagrammed as the supplementary angle. Fe—Pa, femur—patella joint; Pa—Ti, patella—tibia joint; Ti—Bt, tibia—basitarsus joint; Bt—Tt, basitarsus—telotarsus joint.