Figure 13 in Developmental basis of limb homology in Pleurodiran turtles, and the identity of the hooked element in the chelonian tarsus

Figure 13. Scheme of limb development in pleurodiran turtles. These patterns were also observed in other turtles. In the forelimbs (A and B), developmental variation involves the number of cartilaginous primordia of the central series. At advanced embryonic stages and after hatching, secondary fusion may occur in the distal carpal series. In the hindlimbs (C and D), centrale 4 may originate as a distinct cartilaginous primordium, or fuse with the intermedium condensation. The astragalus ossification will develop in the intermedium–centrale cartilage. Abbreviations: I–V, digits I–V; c1–c4, centrale 1–4; d1–d5, distal carpalia/tarsalia 1–5; f, fibulare; F, femur; Fi, fibula; H, humerus; i, intermedium; p, pisiform; Ra, radius; Ti, tibia; Ul, ulna.