Evolutionary biology: Pelvic problems for mammals

So closely has a structure known as the epipubis been associated with marsupial mammals that it has become known as the 'marsupial bone'. The discovery of epipubic bones in fossil specimens that are clearly not marsupial, but are rather of early placental mammals, makes that view untenable. It remains unclear, however, what function this bone had and still has in living marsupials.