Casuariidae Casuariidae The bird family Casuariidae has four surviving members: the three species of cassowary and the emu. All living members of the family are very large flightless birds native to Australia-New Guinea, though the extinct potential member "Hypselornis" was native to India. The characteristics of the family are those of its members. The fossil record of casuariforms is interesting, but not very extensive. Some Australian fossils initially believed to be from emus were recognized to represent a distinct genus, "Emuarius", which had a cassowary-like skull and femur and an emu-like lower leg and foot. A Pliocene Indian ratite, "Hypselornis", has
Bird feet and legs absent in diving birds. For example, in the long-tailed duck, the leg and wing bones are not pneumatic, in contrast with some of the other bones, while loonsand puffins have even more massive skeletons with no aired bones. The flightless ostrich and emu have pneumatic femurs, and so far this is the only known pneumatic bone in these birds except for the ostrich's cervical vertebrae. Fusions (leading to rigidity) and pneumatic bones (leading to reduced mass) are some of the many adaptations of birds for flight. Most birds, except loons and grebes, are digitigrade, not plantigrade. Also, chicks in the