coracoideus

Coracoideus is a Latin anatomical term used to refer to the coracoid element of the pectoral girdle, or, in some contexts, to musculature associated with that region. In English-language texts the bone is usually called the coracoid, while coracoideus appears as the adjectival form or in species-specific nomenclature. The term is encountered across tetrapods, including birds, reptiles, amphibians, and fossil vertebrates.

In the pectoral girdle, the coracoid bone is a stout element that lies on the ventral side of the shoulder and connects the sternum to the scapula. In birds, the coracoid forms a strong brace between the sternum and the shoulder and, together with the furcula, helps transmit wing forces during flight. In many non-avian tetrapods, it contributes to the scapulocoracoid complex and provides articular surfaces for the humerus.

Muscular relationships are also described with coracoideus in some taxa. The coracoid serves as a major attachment site for muscles such as the pectoralis, and in birds for the supracoracoideus, which influence wing movement. The exact attachments vary among lineages, reflecting different locomotor demands.

Evolution and variation: The coracoid’s size, shape, and articulations vary widely among vertebrates. Its presence and relative development correlate with ecological needs such as flight, climbing, or sprawling gait. In mammals, the coracoid region is typically reduced or incorporated into the scapula as a coracoid process, illustrating divergent skeletal evolution.

Notes: Coracoideus appears in anatomical and paleontological descriptions as part of the shoulder girdle’s anatomy, and as a descriptor for related muscular structures.