Costa (coral)

The term "costa," when referring to coral, describes the ridge or raised rib-like structure found on the surface of certain coral skeletons, particularly those of solitary corals (corals that do not form colonies). The costa extends outwards from the theca (the main skeletal wall of the coral) towards the base or attachment point. These costae are important diagnostic features used in coral identification and classification. The morphology and arrangement of costae can vary significantly between different coral species. The presence, absence, and specific characteristics of costae (such as their number, prominence, and ornamentation) are often used to differentiate between closely related species. In some cases, costae may be very prominent and form distinct ridges, while in others they may be subtle or almost absent. The term is derived from the Latin word "costa," meaning "rib" or "side."