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 vertebrae are the rib bearing vertebrae. In order to simplify the mechanics of expanding the chest to breath, the thoracic spine is designed to remain stiff and straight no matter what the body is doing. Spinal nerve emerges above the seventh cervical vertebra; spinal nerve emerges below it.