"Other…" appearing on login screen

Hi

I've got a MacBook Pro mid 2012 running OS X 10.8.5. I was running some commands about the root user on Terminal and suddenly I changed the password of the root user using these commands:

sudo su

Password:*******

passwd

...

& now I see another thing on the login screen named "Other..." which is the root user(Admin) . And its password is the password that I changed using Terminal.(It is the login part for the root user)

I want to get rid of that, is it possible?

I just wanted to remove it using system preferences but it doesn't appear on that part(Users & groups)!

I think it would be possible to delete it using the Terminal.