The phylum Chordata is a taxonomic group. All animals which have a  spine, or backbone, are classified in the phylum Chordata. There  are three subphylums in Chordata: Uroch â¦ ordata (tunicates),  Cephalachordata (lancelets), and Vertebrata (vertebrates).
The 12 vertebrae in the upper back make up what is known as the thoracic spine. They curve outward and inward to provide structure for the rib cage. The bones provide structure and flexibility for the body, while protecting the spinal colu... Read More.
Thoracic Spine Definition The thoracic spine is comprised of twelve vertebral bodies (T1-T12) that make up the mid-region of the spine. This section of the spine has a kyphotic curve (C-shape). The firm attachment to the rib cage at each level of the thoracic spine provides stability and structural support and allows very little motion, which means that thoracic disc injuries are rare.