Because the animal has a spine in addition to the skeleton serves on the weight. The spine is involved in increasing the range of motion. Long spine increases the range of motion.
In addition, because the vertebrate skeleton will serve to weight gain then. Spine is also involved with the increased range of motion. Spine long will improve the range of motion a lot.
For vertebrates, but a skeleton will act in the body weight. The spine is also involved with the increasing range of motion. A long spine will help increase range of motion is derived.