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".

Other articles related to "interclavicle":

Clavicle - Evolutionary Variation
... retained this arrangement, with the addition of a diamond-shaped interclavicle between the base of the clavicles, although this is not found in living amphibians ... evolution of reptiles, and is not found in any living amniotes, but the interclavicle is present in most modern reptiles, and also in monotremes ... and salamanders lack clavicles altogether (although crocodilians do retain the interclavicle), while in turtles, they form part of the armoured plastron ...