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This primitive fin, which Gegenbaur first recognised, is attached to the vertebral column by a simple zone in the shape of a cartilaginous arch. It is also found in modified form in some of the actual sharks and pikes. Human skeleton. Skeleton of the giant gorilla. The little or fifth toe is developed from the lower end of the fin-rod.
The reduction of the radii to four was accompanied by a further differentiation of the fin-rod, its transverse segmentation into upper and lower halves, and the formation of the zone of the limb, which is composed originally of three limbs before and behind in the higher Vertebrates. There is also a complete agreement between the fore and hind limb in the stem or shaft.
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