The Kangaroo and the Emu hold the shield in the Australian coat of arms. Why?

They are animals that only live in Australia.

I wonder if all the kangaroos and emus all over the world realise that they are still actually living in Australia.
Is it part of some master plan where Australia actually owns and rules the world?

Actually, these two animals are on Australia's coat of arms because they cannot walk backwards.

I believe what starry was trying to say is that emus and kangaroos are both native Australian fauna.
Have you ever actually found that being a nit picking meanie has helped you in life at all?

Picking nits is fun. Actually, they hold the shield 'cos it would fall down if they let go.

My suggestion to a government official who wrote an article on the coat of arms for the Australian Government:

The Australian coat of arms pictures two creatures--the
emu, a flightless bird, and the kangaroo.
The animals were chosen because they share a characteristic that appealed
to the Australian citizens. Both the emu and kangaroo can
move only forward, not back. The emu's three-toed foot
causes it to fall if it tries to go backwards, and the
kangaroo is prevented from moving in reverse by its large
tail.

His reply by email:

This may be biologically true but I doubt if this is why
they were chosen...

my bet is it is because they are large, conspicuous and
distinctive elements of the Australian fauna and that they
are of comparable size so would not look incongrouous as a
pair of supporters...

jim