Question: what are the atypical thoracic vertebrae?
Answer: Atypical thoracic vertebrae. The 1st thoracic vertebra is considered an "atypical" because of the complete costal facet for the head of the 1st rib. ... Instead of two 1/2 of costal facets present on typical vertebrae, the 9th thoracic vertebra has only one fovea costalis superior at the upper edge of the body of vertebra.