Final answer:
Costal facets are found on the thoracic vertebrae, specifically for articulation with the head and tubercle of a rib.
Step-by-step explanation:
Costal facets are found on the thoracic vertebrae. The thoracic vertebrae have several additional articulation sites, each called a facet, where a rib is attached. Most thoracic vertebrae have two costal facets on the lateral sides of the body for articulation with the head of a rib, and an additional facet on the transverse process for articulation with the tubercle of a rib.