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.
It is formed by the 12 pairs of ribs, the sternum (breast bone), costal cartilages, and the 12 thoracic vertebrae. These bony and cartilagenous structures form the thoracic cage (rib cage) which surrounds the thoracic cavity and supports the shoulder girdle.