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.
The thoracic cavity is made up of 12 pairs of ribs that connect in the posterior thorax to the vertebral bodies of the spinal column. In the anterior thorax, the first 7 pairs of ribs are attached to the sternum or breastbone by cartilage. The lower 5 ribs do not attach to the sternum.