One of us is tripping balls, because I see no split pin in that photo :S
Ravi, it look to me like that squashed bit is the equivalent of the split pin, ie it stops the nut spinning. Once you pry it up with a screwdriver so that it will no longer interfere with the nut spinning, you should be able to take the nut off in the usual fashion.
Unless of course there IS a split pin, then you'll need to remove that as well.
Touge?
That's what she said
Morning Mang. And other Mangs. And Colin.