Rib arising from a cervical vertebra (cervical rib), or supernumerary rib arising from a thoracic or lumbar vertebra.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 715 (https://doi.org/10.1515/pac-2015-1202)