Fig. 3. Frames from video footage of swimming turtles during forelimb retraction (thrust phase). (A–C) Trachemys scripta, lateral view. (D–F) T. scripta, ventral view. (G–I) Apalone spinifera, ventral view. (J–L) A. spinifera, lateral view. The grid scale is 1 cm in each frame. As in Fig. 2, in lateral views the focal forelimb is the one closest to the viewer, but in ventral views the focal forelimb is the one closest to the bottom of the video frame. Lateral and ventral views for each species are from the same experimental trial, and the trials illustrated are the same as those illustrated in Fig. 2. As in Fig. 2, images in each column depict an approximately equivalent instant in the locomotor cycle: left-hand column (A,D,G,J), early thrust phase; center column (B,E,H,K), mid thrust phase; right-hand column (C,F,I,L), late thrust phase.