It is known that birds have hollow bones to aid them in flight. The fact is that, not all bird species have hollow bones. Some have solids bones (marrow-filled) and is seen in flightless bird species. However, this trait is only seen in ratites and penguins. Emus (Dromaius novaehollandiae) are in the ratites class with ostriches (Struthio camelus) kiwis (Apteryx australis), rheas (Rhea sp.), and cassowary (Casuarius sp.). Which settles that the emu is one of Australia’s solid boned bird.