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.
1 Thoracic spine (upper back) - made up of 12 thoracic vertebrae (known as T1 to T12), which are attached to the rib bones and sternum (breast bone). 2  Because this part of the spine is firmly attached to the ribs and sternum, it is very stable and has fewer problems associated with motion.