Fig. 2.

Ventral view of the left forelimb showing skeletal anatomy and outlines of the paddle/flipper in (A) Apalone ferox, (B) Trachemys scripta, (C) Carettochelys insculpta and (D) Caretta caretta. Outlines of the paddle/flipper end mid-humerus to indicate where the limb protrudes from the shell. Stippling on the humerus of A. ferox (A) indicates the depression of the intertubercular fossa. The humerus of T. scripta (B) is rotated 90 deg posteriorly, providing a posterior view that highlights the dorsally oriented curvature of the bone. The radius is anterior, lateral and ventral to the ulna for each species. Digits I–V are indicated. Images are redrawn and modified from source material [A. ferox (Sheil, 2003), T. scripta (Hall, 2000; Sheil and Portik, 2008), C. insculpta (Walther, 1921) and C. caretta (Wyneken, 2001; Sanchez-Villagra et al., 2007)].