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DEVONIAN PERIOD

416-359 million years ago

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Ancestral rhipidistian fish evolved pectoral fins with bones homologous to the humerus, radius, ulna, and carpals of tetrapods and pelvic fins with bones homologous to the femur, tibia, fibula, and tarsals of tetrapods.

The first vertebrates to evolve a humerus were the rhipidistian sarcopterygians which preceded the amphibians. They possessed a joint in the region of the elbow, although the rest of the fin was fairly stiff (Carroll, p. 161). Before the evolution of amphibians, rhipidistian fish evolved two bones to articulate with the humerus, the radius and ulna.The fish ancestors of amphibians possessed small bones in the region of the wrist and cartilaginous fin rays in the region of tetrapod fingers. Rhipidistians possessed an ulnare and intermedium of the wrist (Carroll, p. 163). Rhipidistian fish possessed a femur which included a joint in the area of the knee, although the rest of the fin was fairly stiff (Carroll, p. 161). In rhipidistian fish, the tibia and fibula possessed a hingelike connection with the femur (Carroll, p. 163).
Rhipidistian fish possessed a fibulare and intermedium homologous to two tarsal bones of the tetrapod foot (Carroll, p. 164)