part of part of in taxon connected to connected to contributes to morphology of Tetrapoda Serpentes Homo sapiens system thoracic segment of trunk sternum http://upload.wikimedia.org/wikipedia/commons/1/12/Illu_thoracic_cage.jpg MA:0001331 AAO:0000765 GAID:246 breastbone galen:Sternum BTO:0001302 Single element that constitutes the postzonal area of the pectoral girdle.[AAO] UBERON:0000975 It probably first evolved in early tetrapods as an extension of the pectoral girdle; it is not found in fish. In amphibians and reptiles it is typically a shield-shaped structure, often composed entirely of cartilage. It is absent in both turtles and snakes. In birds it is a relatively large bone and typically bears an enormous projecting keel to which the flight muscles are attached. Only in mammals does the sternum take on the elongated, segmented form seen in humans. In some mammals, such as opossums, the individual segments never fuse and remain separated by cartilagenous plates throughout life FMA:7485 While its developmental origins are similar to the ribs (from the myospetum and septum of the trunk region), it is often associated with the pectoral skeleton, due to both function and physical connections (i.e. the coracoid of archosaurs). It may be a single element or a series of smaller structure (sternebrae). Based on Kardong 2012. [PHENOSCAPE:ad]. EHDAA2:0001914 A midventral endochondral skeletal element which represents the origin site of the pectoral muscles[PHENOSCAPE:ad]. relationship loss: part_of postzonal element (AAO:0000938)[AAO] vertebrate sternum in birds, either ratite (no keel or carina) or carinate (keel and carina present) Wikipedia:Sternum SCTID:302522007 EHDAA:9561 in EMAPA and EHDAA2 this is part of the skeleton of pectoral girdle; the classic def of pectoral girdle (see WP) excludes the rib cage and sternum MESH:D013249 Fishes lack a sternum. (...) A sternum is absent in the first fossil tetrapods, but it is present in modern amphibians. (...) Thus, a sternum occurs in some modern amphibians, birds, mammals and archosaurs. However, its absence in the common ancestors to these groups means that it has arisen independently several times within the field of the midventral connective tissue.[well established][VHOG] UMLS:C0038293 CALOHA:TS-0972 EMAPA:18344 NCIT:C12793 VHOG:0000856 sternal rib thoracic rib cage thoracic segment organ pectoral girdle skeleton endochondral element T Alexander Dececchi Christopher J. Mungall