The images above all illustrate the presence of a vestigial structure. What is this structure and why is it no longer used for its original function? A) Sacral vertebrae have disappeared in modern man. They are no longer needed as man stood more and more upright. B) Lumbar vertebrae. As man became bipedal, the vertebrate became shorter and wider. These particular vertebrate disappeared. C) Coccyx or tailbone is the remnant of a lost tail. The tail was used for gripping as well as an aid in balance and mobility. D) Iliac blade. This part of the pelvis was shortened and widened as a requirement for keeping the center of gravity stable while walking.