#sternum

• Ratite — A scientific term designating any flightless running bird of the order of ratites (Struthioniformes), anatomically characterized by severely reduced wings and, specifically, a flat sternum completely lacking a keel (carina), a bony structure essential for anchoring the pectoral muscles required for flight. As an evolutionary consequence, these birds (such as the ostrich, emu, cassowary, or kiwi) permanently lost the capacity for flight, developing powerful legs specialized for high-speed running instead.
• Axiphoidia — A rare anatomical condition or structural anomaly characterized by the congenital absence, incomplete development, or alignment anomaly of the xiphoid process, the lowermost terminal element of the sternum. This morphological feature can influence the delicate insertion of abdominal muscles and the diaphragm, requiring clinical monitoring if it causes respiratory or structural discomfort within the rib cage.