An interclavicle is a bone which, in most

tetrapods Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...

, is located between the clavicles.

Theria Theria (; Greek: , wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes. ...

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...

(

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

and placentals) are the only tetrapods which never have an interclavicle, although some members of other groups also lack one. In therians, it is replaced by the

sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...

which is similar in shape and function but forms via

endochondral ossification Endochondral ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is produced. Unlike intramembranous ossification, the other process by which bone tissue is produced ...

(cartilage forming bone). The interclavicle, on the other hand, develops through

intramembranous ossification Intramembranous ossification is one of the two essential processes during fetal development of the gnathostome (excluding chondrichthyans such as sharks) skeletal system by which rudimentary bone tissue is created. Intramembranous ossification i ...

of the skin.

Monotreme Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals ( Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brai ...

s, although part of the mammalian class, do have interclavicles.

References

Bones of the upper limb Vertebrate anatomy {{Vertebrate anatomy-stub