Fig. 6.

Lateral view of the paths taken by the distal-most point of the forelimb (digit 3; tip of the flipper in Carettochelys insculpta and Caretta caretta) for C. insculpta (red squares), Apalone ferox (blue inverted triangles), Trachemys scripta (green triangles) and C. caretta (black circles) showing the amount of anteroposterior and dorsoventral motion relative to the turtle’s body throughout the limb cycle. Coordinate positions of X and Z throughout the swimming cycle were smoothed and interpolated to 101 points. Paths are the average of all trials for each species, and have been scaled to unit size to facilitate comparisons of trajectories. Paths start at the origin. Position of the shoulder relative to the path is indicated for each species with a color-coded cross. Despite greater dorsoventral motion in T. scripta, the trajectories of A. ferox and T. scripta (rowers) are both horizontal. Caretta caretta (flapper) approaches (but does not attain) a vertical trajectory. Finally, in C. insculpta, the trajectory of the tip of the flipper is intermediate between A. ferox/T. scripta and C. caretta. The ratios of dorsoventral to anteroposterior motion of digit 3 designate A. ferox, T. scripta and C. insculpta as rowers (ratios less than 1: DV/AP=0.23±0.01, 0.29±0.01 and 0.58±0.03, respectively) and C. caretta as a flapper with a ratio greater than 1 (DV/AP=1.47±0.13).