Anyone who has eaten roasted chicken can account for the presence of a long,spine-like bone in the drumstick. This is actually the fibula, one of the two long bones of the lower leg (the outer one). In dinosaurs, and the ancestors of birds,this bone is tube-shaped and reaches all the way down to the ankle. However, in the evolution from dinosaurs to birds, and it lost its lower cessation,and no longer connects to the ankle, being shorter than the other bone in the lower leg, or the tibia. Scientists noted long ago that bird embryos first develop a tubular,dinosaur-like fibula. Afterward, it becomes shorter than the tibia and acquires its adult, or splinter-like shape.
Source: phys.org