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.
There are 12 thoracic vertebrae situated in between the cervical and lumbar vertebrae. The major characteristic that is unique to thoracic vertebrae is the presence of costal facets for articulation with ribs. These costal facets can be seen on the sides of the vertebral bodies and on the transverse processes.