Interclavicle

An interclavicle is a bone which, in most tetrapods, is located between the clavicles. Therian mammals (marsupials and placentals) are the only tetrapods which never have an interclavicle, although some members of other groups also lack one. Monotremes, although part of the mammalian class, do have interclavicles. In birds, the interclavicle is fused with the clavicles to form the furcula (wishbone). In chickens the furcula forms a "Y" shape and the interclavicle is the stem of the "Y".