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 ribs are anchored to the spine by the planar joints formed between the vertebrae and the ribs. The first nine thoracic vertebrae (T1 through T9) contain a pair of demi-facets, where a facet is split between two adjacent vertebral bodies.