Fig. 8. Mean kinematic profiles of forefoot (paddle) orientation during turtle swimming. (A) Trachemys scripta, (B) Apalone spinifera. The format and method of profile calculation are the same as in Fig. 4. The angle plotted is the angle between a vector pointing forwards along the anteroposterior midline of the turtle and a vector emerging from the palmar surface of a plane defined by the wrist and the tips of digits 1 and 5 on the turtle manus, transformed by subtracting 90° from each value. Thus, a low-drag orientation of the forefoot (perfect feathering) is indicated by an angle of 0°, whereas a high-drag forefoot orientation, with the palmar surface of the manus facing in the direction opposite to the direction of travel, is indicated by an angle of 90°. The bold vertical line in each plot demarcates recovery phase (R) from thrust phase (T).
